Archive for the ‘Digital Photography’ Category

Should I Get a DSLR?

August 27, 2011

Please understand at the outset, these are my opinions.  If you disagree with them tell your friends, please don’t tell me.  If you find something  factually inaccurate let me know.

I can’t update this article every time new cameras come out, so the cameras mentioned in the article are obsolete now.

Ansel Adams, maybe the worlds most renown photographer said, “The single most important component of a camera is the twelve inches behind it.”  Good photographers make good pictures with any camera — poor ones make poor pictures with the best of equipment.

SLRs were the way to go in film days when there were no reasonable alternatives.  But, those days are long gone.  In the modern world of digital cameras the options are very different.

July 2010 Update People who read this article ask me which Prosumer camera I recommend.  My recommendations are not based on my testing, rather they’re based on reviews by major camera/photo websites. You can see one such article Here.

There’s a lot of misinformation on the web about the difference between DSLR and non-DSLR cameras.  I think much of this stems from snobbery on the part of a few camera buffs who fancy themselves amateur photographers and from marketing motives.  There’s a lot more money to be made in DSLRs than non-DSLRs.

Part of the misinformation is aided by dividing digital cameras into only two groups, DSLRs and P&S (point & shoot).  For the purposes of this article I am going to add a third group between P&S and DSLRs.  For lack of a better term I call it Prosumer (also called DSLR-Like or Super Zoom).  I once understood the term Prosumer to mean what I use it to mean in this article, but apparently it has been misused and discarded.  The term Point & Shoot should be restricted to those digital cameras that are largely or fully automatic — the camera decides everything and you pretty much have to use what it decides.  If you don’t like the word Prosumer substitute ‘bridge-camera’ or DSLR-Like or any word you like for it in this article.  I’m just trying to have a term for a high end one-built-in-lens camera.

When I see comparisons between types of digital cameras they’re almost always between DSLRs and P&S cameras.  I sometimes think they’re written by people who’ve never used a Prosumer camera or don’t know they exist.  They say things like “If you continue to take pictures you will want control over the camera, and that requires a DSLR.”  This is simply wrong.  Prosumer cameras have essentially all the controls a DSLR has.  The ability to control the image creation and camera is not meaningfully different between the two kinds of cameras.  You can control, aperture (F-stop), shutter speed and focus.  You can operate them entirely manually if you choose, but the auto-focus and auto-exposure functions have the same features.  Depending on the Prosumer camera you choose, you can use RAW images.   These comparisons also say, “All DSLRs feature interchangeable lenses, so you can change the focal length to your preference, rather than being stuck with the limited lens common to a point-and-shoot.”  Wrong, wrong, wrong.  In fact it’s exactly the opposite.  The limited camera in this arena is the DSLR.  A Prosumer camera’s zoom lens can go from 28mm to 500 or even 1000mm.  Five hundred millimeters is more telephoto than you’re likely to ever buy or lug around for a DSLR.  In addition to cost, small, light, and long telephoto zoom is the Prosumer camera’s big advantage over DSLRs.

Here are the advantages and disadvantages of DSLRs:

Advantages of DSLR:

  • Less digital noise at high ISOs (though this is changing)
  • Faster shutter response (important for action shots)
  • True through-the-lens manual focusing for close-ups & extension tubes
  • A little larger F-stops (for a price)
  • Shallower depth of field to blur distracting backgrounds/foregrounds

Disadvantages of DSLR:

  • Larger, heavier, bulkier than Prosumer cameras.
  • Have to buy extra lenses to get the range of focus
  • Have to carry these extra lenses (camera bag – not just camera)
  • Dust is more likely to get inside and on sensor
  • Long zoom lenses are larger/heavier/very expensive with less zoom
  • Have to be farther from the subject without special lenses (~ 2′ vs 3-5″ with prosumer)
  • Shallower depth of field: harder to get both far and near objects in focus
  • More expensive than Prosumer cameras

Digital Noise

This is the main advantage of DSLRs over Prosumer cameras.  Digital noise is like grain in film.  The colored specks you see in the image at right are digital noise.  I have deliberately chosen a very noisy picture to show what noise is. This picture was taken at ISO 400 with an older Prosumer camera.

ISO is a number that represents how sensitive the camera is to light. Said another way, it determines how well lighted the subject has to be to take the picture.  The higher the ISO the darker it can be and still take pictures.  On digital cameras you can vary the ISO setting.  If you use a Prosumer camera at normal ISOs (80-100) you aren’t likely to have problems with noise.  But, as you go above 200 the noise gets progressively worse.  Above 400-800 you’re likely to get poor quality images. Whereas with a DSLR you can use ISOs of up to 3200 and still get acceptable quality images.  If you edit your pictures on the computer, there are programs such as NoiseNinja that help remove noise.  But, shooting action, such as sports, after dusk is one of the rare situations where a DSLR with a 400mm lens has a clear
advantage over a Prosumer camera.  And, if it’s your intention to shoot a large proportion of your  pictures in low light without flash a Prosumer may not be the camera for you.  That said,  I took this shot of my grandniece’s ballet recital from the back of a large auditorium with my Prosumer.

Shutter Response

There’s a delay between when you press the Go button on a camera and when the picture is actually taken. This delay is greater on non-DSLR cameras and people taking action shots are often frustrated by it.  This delay is much less today than it was on early non-DSLR digital cameras, but DSLRs are still faster.  However, there’s more than one way avoid this delay when using a Prosumer camera.  I’ll only mention one here.  The delay is due to the camera having to figure out what F-Stop & shutter speed to use and (mostly) where to focus.  Point the camera at the location you intend to shoot and look at the settings the camera has determined (they’re usually shown in the viewfinder), change the mode to manual and set the camera to those same values then set the focusing to continuous.  Now the camera doesn’t have to figure them out, so it shoots about as fast as a DSLR.  If you want to shoot machine gun fashion (shooting picture after picture continuously while holding the shutter release down) the DSLR may (or may not) shoot slightly faster — maybe 5 vs 4 frames per second.

Trough-the-Lens Viewing

With a DSLR you’re actually looking at the subject through the lens of the camera.  With a Prosumer camera you’re looking at an image of what the camera sees on a little monitor in the viewfinder. For great the majority of picture taking you won’t notice the difference and even forget you aren’t looking at the real thing.
But, if you do super close Macro photography — if you want to fill the frame with a bugs eye — focus becomes critical and you may want to do it manually instead of letting the camera focus automatically.  In this case you need to see the real object clearly enough to focus sharply.  Prosumer cameras have features to assist with this, but it’s not like seeing the real thing.  Also, because you can remove the lens, you can put what are called extension tubes between the camera and the lens to create extreme close-ups.  This said, some truly spectacular macro photography is done with Prosumer cameras and some people argue it’s actually better for Macro photography, partly because of the greater depth of field.  Extreme close-ups have a very shallow depth of field.  Also, the resolution of Prosumer view finders are getting better and better.

Shallow Depth of Field

Depth of field is the distance between the object nearest to the camera and the most distance object that are both in focus.  Depth of field is a mixed bag.  Sometimes you want a lot and sometimes you want only a little.   Sometimes you want to make the objects in front or behind the subject go blurry so they don’t detract from what you are trying to show.  In this case you want shallow depth of field.  In the picture at the right you can see the tractor and the closest words in the label are blurry.  Other times you want everything you can get in focus, in which case you want great depth of field.  Greater depth of field is usually an advantage in Macro photography.  The greater depth of field with a Prosumer camera may compensate for the lack of through-the-lens viewing, because DSLRs have quite a bit less depth of field than Prosumer cameras making it hard to get the entire bug’s eye in focus.

Discussion of Cons

With the Prosumer Canon PowerShot SX10 IS (and others) you get a zoom range of of 28-560mm.  (UPDATE: The Nikon Coolpix P100 reaches from 28mm to almost 700mm & the Olympus SP-800 is 28mm to 840mm.  If you could get such a lenses for a DSLR, which you can’t, it would be too heavy to carry.)  To get a 28-500 zoom range with a DSLR you have to buy a wide angle lens and a long telephoto (and one or two more lenses to cover the midrange). A top quality 500mm telephoto from a major manufacturer like Canon can cost $6000 and the lens alone will weigh 8.5 pounds. But, you’re more likely to end up with is a 70-200mm zoom lens which can cost about $1600 and weighs about 4 pounds.  From a cheap lens maker this lens will cost $900.  Together these make for about 6 pounds of camera and lens. You can get a cheaper lighter lens in 70-200mm range but it won’t have an F-Stop advantage over the Prosumer.  To get the 28mm you have to buy another lens.  If you want to get close to your subject (something the size of a Zippo lighter) you have to have a special lens.  All in all you can spend a small fortune on lenses.  Then, you have to carry these lenses with you when you plan to take pictures, and change them as the need changes.  And, when you take the lens on and off a DSLR you expose the inside of the camera to dust or trash blowing into it, and onto the sensor — the heart of picture taking with a digital camera.

Whereas with a Prosumer camera  you can get a zoom range of 28mm-500mm+ all in one complete camera weighing less than 1.5 pounds, for about $450. That’s about what the body alone of a DSLR weighs with no lens. And, it’s the camera manufacturer’s lens (the lens on my Prosumer camera was made by Leica — the prince of lens
makers).  Also, with this lens you can just about fill the picture with that Zippo lighter.

Another advantage of Prosumer cameras is they can use flash at all shutter speeds.  This can be a real advantage if you want to present your subject against an all dark background.  An electronic flash is faster than any shutter speed.  This means you can set the shutter speed on your Prosumer to it’s highest setting and the flash will still light the picture correctly.  There are two advantages to this.  1)  If the area around you is lighted, just not enough to take the picture, if you use a slower shutter speed this existing light will partially light your picture and give a ghost image of the surrounds and a blurry ghost image if you move the camera.  This problem is eliminated if you set the shutter speed high.  2)  You often see close-ups of insects or flowers where the background is dark.  This is a nice effect which you can get by using a shutter speed high enough only the flash will light the object and the more distant

background will go dark.  You can’t do any of these things with a DSLR.  DSLRs use a special kind of shutter called a “focal plane shutter”  that limits the shutter speed with electronic flash.  I have a recent DSLR and the highest shutter speed that can be used with flash is 1/200 second.  A Prosumer camera can use it’s full range of shutter speeds, as high as 1/2000 second or higher.  This will eliminate the ambient light in any interior shot and many exterior ones.

I’m 78 years old and have been taking pictures since I was 14 (actually 6, but I only got something more than a box camera at 14).  I had a wet darkroom in my home during my forties and have probably read a couple or three hundred books on photography.   All this isn’t to say I’m a hotshot photographer, I’m not, rather it’s to explain I’m not a newbie.  If you’re going to devote your free waking life to photography, and are willing to tote a bag of gear and a tripod everywhere you go then by all means gear up with a DSLR, but before you do, get a good Prosumer camera and give it a try for a month or three so you’ll know what you’re really getting for all that pain.

If sensor technology continues to improve, DSLRs may someday become the dinosaur of digital photography.

Scanning vs Upsampling to Enlarge

June 21, 2008

mea culpa

I have to eat some crow and apologize to Steve. In the HAL-PC digital photography SIG on Saturday June 21,2008, I gave some advice and made statements about this subject that were in one case probably wrong and in another uncertain.

Technology had passed me by. A few years ago home flatbed scanners could not really (optically) scan at resolutions above 300-600 ppi. As I understood the example given in the meeting, the question was, “If you are going to scan a 2″ x 2″ print and enlarge it to 8×10 inches should you scan at 300 ppi and upsample to get the required resolution or should you let the scanner produce a scan of the required resolution.”

To be clear at the outset, if you scan and enlarge a print more than a modest amount the result will be a degraded picture. This article assumes you want make such an enlargement anyway and are prepared to accept a poorer result.

First, except in rare circumstances, no more image content/detail can be obtained by scanning a print at greater than 300 ppi. So, to make a bigger print, in one way or another pixels must be generated that do not increase image detail, but instead simply “pad-out” pixel count.

To scan a 2″ print and enlarge it to 8″ requires a 4x increase in resolution. If you want to print the image at 300 ppi and 8″, four times 300 ppi is 1200 ppi. One can either scan the small print at 1200 ppi or scan it at 300 and upsample 4 times in your photo editor. Until recent years if you scanned a print at more than about 600 ppi the scanner interpolated/upsampled (faked in pixels) to create the higher resolution. I said in the meeting the upsampling algorithm in your photo editor will probably be as good as, and maybe better than the one used by the scanner, thus if I must enlarge a print I scan at 300 and upsample in Photoshop. In saying the scanner must upsample the image to get the higher resolution, I was probably wrong. That’s no longer necessarily true.

I rarely have occasion to upsize a print, and the world changed while I wasn’t paying attention. Today it’s common to have home scanners that will produce real scans at 2000+ ppi. So, my statement that to make a marked enlargement the scanner must upsample is no longer true. If you have a modern scanner it can probably scan at 1200 ppi or more without upsampling. Thus, today the choice is between increasing the scanner resolution beyond the useful picture content it can produce in order to pad-out the extra pixels, or scan at the highest meaningful resolution (300 dpi) and upsample in your photo editor.

After doing some some Googling, I haven’t found an understandable discussion of this choice. Some theoretical considerations suggest if there’s any difference you may get smoother edges in high contrast areas, but my tests didn’t bear this out. And, in making these illustrations I found it was much faster to scan at 300 dpi and upsample, so one downside to using higher resolution scans is, it takes longer. I asked a authority on scanning and scanners whose opinion I respect and he said,”My opinion is neither method will be very satisfactory but the larger scan is your best shot.” For reasons that are unclear to me, my tests did not bear this out.

When doing my tests I found that using the bicubic “smoother” algorithm, which Adobe recommends for upsampling, produced a loss of image definition compared to the higher resolution scans. Regular bicubic did not cause this loss. The illustrations I link to below use regular bicubic.

Unfortunately, I wasn’t able to put my hand on an ideal image to illustrate the difference. To my eye these results of using the two methods seem to give better definition using upsampling. Perhaps there’s a sharpening effect from the bicubic algorithm.

The images in my tests were scanned from a sharp 4×6 print.

I couldn’t figure out how to make “mouseover” comparisons in this blog editor, so Click Here to see the results of my trials.

The images are fuzzy because they have been magnified 2 1/2 & 4 times the maximum useful resolution of these prints as would be required to print 4 x 6 scans as 16 x 24 — 4x, or to print them at 10 x 15. This is the same as enlarging a 2 x 2 print to 8 x 8 or 5 x 5 respectively. Thus such a large size change is going result in a big blurry image.

Below is part of the image from which the samples were taken. It’s shown at a reasonable resolution — about 250 ppi. This crop a small portion of the original picture.

.

As I said earlier, these pictures are not ideal for illustrating the difference between the two methods. To best illustrate the difference the picture needs to have some high contrast shapes, like a clock face or the text on a sign. If I run across a better picture for this I’ll swap these out.

When Using Flash, Is AUTO White Balance (AWB) Really Used?

July 21, 2007

At the July 21, 2007 HAL-PC Clear Lake Digital Photography SIG meeting there were a couple of questions/issues of disagreement. This article covers one of them. If I find time I will prepare an article on the other later.

When using Flash with white balance set to AUTO, does the camera in fact not use the AUTO white balance after all, even thought it says in the EXIF that it did?

I wasn’t able to find a definitive answer to this question on the web. My guess is it isn’t stated because AUTO white balance is used when the EXIF data says it’s used, thus no one sees a need to post articles stating something that’s normal/as expected/as assumed.

Below is some of the little I’ve found on this. My indirect conclusion from these references leaves me assuming AUTO white balance is used with flash in the same way it is used with any other light source(s). An exception would be some cameras that have a special “Flash white balance.” A subset of these cameras switch to this mode when shooting Flash. The only cameras I know of that have Flash white balance are DSLRs, which most people don’t have. But, the very fact that they have a Flash white balance mode must mean it’s different from AUTO white balance. None of the five digital cameras I have owned have/had a Flash white balance mode. But, if one your camera has one and it is used, I assume (and hope) the EXIF data would say that, thus making it clear AUTO white balance was not used.

This article has examples of pictures shot under various modes. This camera used has a Flash mode and the images illustrate that the image shot in AUTO white balance have a different color balance than the one shot in Flash white balance.

This post says:

“There’s no doubt that all of the test photos shot on the Flash white balance setting (including mine, yours and Bruce’s) are off-color. And it’s also true that the photos shot on Auto white balance appear to be much better.” [emphasis added]

Again, this statement makes a clear distinction between shots made in AUTO white balance and those made in Flash white balance.

This article says:

“So, here I am on Auto WB and using flash. . . . because the D2x is functioning in a “mixed” lighting environment, it must deal with both types of light…the 5400K flash, and the 4200K fluorescent” [emphasis added]

The statement clearly suggests his Auto WB is taking into account all sources of light, not just the flash.

Again, this post says:

“Auto WB does a great job on my D70. Even when my SB-600 [flash unit] fires. I’m pretty sure the camera’s on-board computer calculates the optimum WB after the image is recorded. Which makes sense. I wouldn’t want it effectively fixed at the “Flash” temperature just because I have a flash unit attached. I may be shooting fill flash . . .”

Obviously, the confidence you can place in the above references is limited.

The following reasons leave me believing AUTO white balance works the same with flash or without.

  • the EXIF data says AUTO white balance was used
    in mixed lighting images using fill flash would not be properly balanced if not corrected AUTOmatically
  • the implications of above references
  • the absence of links to the contrary
  • my experience

If a camera is using Flash white balance, it is not using AUTO white balance, and I assume this is made clear in the EXIF data.

Someone suggested there were different meanings for AUTO white balance — one meaning when using flash, and an entirely different one at other times. I think this is unlikely.

I welcome any clear/unambiguous and authoritative references that will settle this question without having to read between the lines.

Get More Pictures on Your Camera’s Memory Card

April 22, 2006

Fewer Pixels or More Compression?
posted April 16, 2006

At the last HAL-PC Clear Lake Digital Photography SIG (Saturday 4/15/06) the question came up whether increasing JPEG compression or reducing the number of pixels recorded will result in the better image.

Sometime you may find yourself in the situation where you don’t have enough memory/storage space to record all the pictures you want to take — for example, you’re on a weekend trip and only have a memory card that can record 100 pictures at the best quality. Depending on your camera you may be able to increase this to 400-800 pictures by sacrificing a little image quality that you may never miss.

There are two way to increase the number of pictures you can record in the same space. One way is to decrease the number of megapixels you record for each picture. The other is to increase the JPEG compression used to store each picture. Either method sacrifices some picture quality. This raises the question of which method will result in the better image — which prompted this article.

NOTE: In this article the terms megapixels, MP, number of pixels,
and resolution all mean the same thing and are used interchangeably

JPEG is a “lossy” file format. The JPEG method of image storage can achieve a remarkable amount of compression (reduction in file size). It can reduce the file size by a factor of 20 and still have a reasonably good image. But, there’s no free lunch. To achieve its remarkable compression it throws away small amounts of the original image, and the greater the compression the more of the image gets thrown away. On the other hand, using a lower number of pixels to record the image results in an innately lower fidelity image. So, which method is best?

To create this demonstration I took two shots. They were taken with my 8 MP (megapixel), Olympus 8080 camera. The high resolution shot was taken at 8 MP (3254 x 2448), and the lower resolution shot at 2.8 MP (2048 x 1336). 2.8 MP was selected for the lower resolution because it produces roughly the same file size as the higher resolution when using increased JPEG compression. The target was a piece of striped cloth. The two shots were taken one after the other with the camera on a tripod.

The image on the left in both the upper and lower pair is the same crop from the shot taken at higher resolution and lower quality (higher JEPG compression). The image on the right in both pairs is same crop from the shot taken at lower resolution and high quality (low compression).

For the images to be comparable they must be the same size (same resolution/PPI). To do this, the low resolution image must be up-sampled (made larger) or the high resolution must be down sampled (made smaller). Anticipating an issue over which of these methods might yield the best results I have done it both ways. The pair on the top were done by up-sampling the low resolution image, the bottom pair were done by down-sampling the high resolution image (and magnified to make them large enough for comparison). Other than this, the upper and lower pair are the same — that is, the same crops from the same two images.

__________________
High Resolution
High Compression
File Size 1503Kb
Low Resolution
Low Compression
File Size 1605Kb
The low resolution shot above has been up-sampled to make the images the same resolution/PPI
The high resolution shot has been sampled down to make the images the same resolution/PPI.  The down-sampled pair has been magnified so the images are large enough to compare conveniently
__________________

Conclusion

To my eye the higher resolution/higher compression
images on the left, are clearly (pun intended) sharper


Addendum

So, if I’m right and you need space for more pictures, first increase the JPEG compression. That is, choose a lower “quality” setting. If that still doesn’t give you enough pictures, start lowering the number of pixels (resolution). Step down through each lower resolution until you reach the number of pictures you need. I probably wouldn’t go below 1600×1200 (2 megapixels) if you intend to print your pictures. If you only intend to display them on a computer or TV you can go down to 1200×900 (1 megapixels). It’s important to remember, reducing the number of pixels you record limits the amount of cropping you can do and still have enough pixels for a good print.

I recommend you experiment with this by shooting and printing at the higher quantity settings before using them on something you can’t do over if the results aren’t good enough for you. Following this procedure on my camera with a 512 MB memory card, you would see the following increases in space available for pictures.

Resolution/Compression Setting Megapixels photos Shots Times X
3264×2448 / low compression 8 MP 130  
3264×2448 / high compression 8 MP 260 2
2592×1944 / high compression 5 MP 410 3
2288×1712 / high compression 4 MP 515 4
2048×1536 / high compression 2.8 MP 638 5
1600×1200 / high compression 2 MP 1000 8
1280×960 / high compression 1.2 MP 1600 12

One thousand shots is the equivalent of about 30, 36 exposure rolls of 35mm film; or 50, 20 exposure rolls..

JPEG Compression — Devil or Angel?

April 21, 2006

JPEG Compression — Devil or Angel?
posted April 23, 2006

You only have to fool with digital photography a short time before someone says something like, “Try to avoid JPG, it degrades your images, and each time you save the image it becomes worse and worse.” And they may add, “You need to buy a camera that supports RAW images and use that exclusively.” In this article I will try to shed some light on the pros and cons of using JPEG normally call JPG. JPEG is simply a file compression method. To identify files compressed using the JPG method they’re given the extension jpg (The letters after the dot at the end of a filename are called the extension.). Digital images tend to be large and so use a lot of storage space (and web resources). To combat this, ways of compressing image data have been devised. By far the most widely used compression method is JPEG. [GIF and PNG are also compression methods. They are best suited to graphical images that only have discrete colors.]

The JPEG method of image storage can achieve a remarkable amount of compression (reduction in file size). It can reduce the file size by as much as a factor of 20 and still have a reasonably good image. But, it’s not a free lunch. To achieve its remarkable compression it throws away small amounts of the original image data, and the greater the compression the more of the image gets thrown away/lost. For this reason it’s called a “lossy” compression method. This is why people are warned against using JPEG.

I’ll start by saying if it’s about as easy for you to record/store your images in one of the lossless format such as TIFF or RAW, by all means do so. But, it’s impractical to use large uncompressed images on the web and they bog down email, particularly for those who use dialup. And, let’s say you can take 100 of the highest quality (least compression) JPEG pictures on your camera’s memory card. You’ll likely only be able to take about 15 pictures using TIFF. Also, you may be able to shoot 6-10 pictures in rapid succession using JPEG, where you’ll have to wait 10 to 20 seconds between shots for the camera to finish recording each TIFF picture.

You’ll hear people talk about JPG artifacts. They may say saving an image over and over in JPG is like passing it through a copy machine repeatedly — the image degrades every time you save it. I hope to to shed some light on these things.

Disclaimer — I am not expert in these areas. For example, I don’t know how the JPEG compression algorithm works. I will simply show you some images I have fooled around with in PhotoShop, and tell you what I think they show and let you judge for yourself.

For these illustrations/comparisons I want you to see the pictures side-by-side. In order to do this I will sometimes use the same pictures more than once. When I use the same caption name, it is the same picture. The original picture used in these illustrations is at the top of the page. I’ve magnified the demonstration images to make differences more apparent, so the image named “Original X3” is the original picture magnified three times.

This first illustration is a comparison of the original (magnified 3 times) with a JPEG of the same image using moderately aggressive compression (50 in PhotoShop’s Save For Web). You may not notice much difference at first, but as you study the image on the right you will begin to see areas where it is disintegrating. Look carefully near the outer edges of the upper petals. Also, look on the petals around the yellow “eyes” Also, at the small petal at the 4 o’clock position. This is JPG artifact.

Original X3 1st generation JPG of original

Below, when you compare the original with the same JPG compressed image in actual size (not magnified) you don’t see the artifact, but of course, you and I know it’s there, so our obsessive selves can brood about it.

Original 1st Gen JPG

Now about the copy machine analogy. The picture on the left below is the same as the one above on the right. The picture below on the right is this very same picture saved ten more times using the same compression (50 in PhotoShop’s Save For Web). The first generation of compression left obvious JPG artifacts, but many subsequent saves at the same compression level caused no further degradation. And, I’m not even a guest star on Mythbusters. The answer is, as long as you use an amount of compression less than or equal to the amount used for the first JPG it will not further degrade the image — the damage has been done, but it’s not made worse. Nonetheless, for reasons too messy to explain here it’s my opinion that repetitive saves in JPG are almost always unnecessary and should be avoided.

1st generation JPG of original 11th generation JPG

The following is an illustration of what you get when minimal JPEG compression (75 in PhotoShop) is used. Now that you know what you’re looking for you can probably find the minimal JPG artifacts in the image on the right, but they’re fairly minor and you would certainly never see them in the actual size image.

Original X3 Minimal JPG compression

To demonstrate that you cannot tell the difference, the final two images below are similar to the two images above, except they’re normal viewing size — that is, not magnified. Like the above left image, the below left image has no JPEG compression. Like the above right image the below right image has been JPEG compressed, and by the same amount (75 in PhotoShop). I can’t see any difference. Can you?

No JPEG compression Minimal JPEG compression

I end by repeating, lossless file formats maintain the full fidelity of your images, so by all means use them whenever practical. However, it’s my opinion that modest JPEG compression does not do serious damage to your images even if you compress/save the same image time and again.

JPG Compression — Part 2

April 20, 2006

Iterative Compression, With Changes
posted April 30, 2006

This is an attempt to address the issue Johno raised in his Comment to my previous article “JPEG Compression — Devil or Angel?” If you haven’t read that article it may make it difficult to understand this one, so I urge you to read it first.

In the earlier article we established that repeatedly saving the same image at the same or less compression does not further degrade the image. But, when changes are made to the image between saves the effects of the compression will be somewhat different, raising the question of whether, and by how much, this causes further observable degradation. For this test I repeatedly made a modest (not small and not major) Curves adjustment to the image. Though each adjustment was modest, the cumulative effect of these adjustments was a major and unacceptable increase in image contrast. For the reference/control I repeated the adjustment to the image in PhotoShop four times and then saved it with the same moderately aggressive compression I used in the first article (50 in PhotoShop’s Save For Web). For the test image I started with the same image used for the control (the original from the earlier article). After making the first adjustment, I saved it (50 in PhotoShop’s Save For Web). I then loaded this first generation JPG image in PhotoShop, repeated the adjustment, and repeated the JPG Save For Web; creating a second generation JPG. I repeated this procedure two more times creating the third and fourth generation JPG.

To be clear: for the control, the adjustment was applied four times, ending with one JPEG save. For the test image, after each adjustment the image was saved as JPG — this JPG was then used to make and save the next JPG, etc., such that the final test image included four adjustments and four JPEG compressions. The two images below show the result. Though the two are different I’m not sure which is better. In some areas the control looks better, in others the test image looks better. Neither seems obviously superior to me overall. Both seem about the same amount different/distant from the original — your opinion may differ.

Images below are magnified by three.

 


Reference/Control

Test Image — 4th Generation JPEG

Below you can compare the single JPEG compression from the original article with the control image in this test. Each image has been subjected to only one JPEG compression, but the contrastier reference/control image has more conspicuous JPG artifact. I included this comparison in case you were thinking, ‘Wait! Something else is different — the artifact are more prominent in both of the images in this test. They are; apparently because the image is more contrasty.

 


1st generation JPG of original

Reference/Control

 


Original X3

I have included the original image so you can see where we started before any adjustments or JPEG compressions.

© Copyrighting Photographs

March 30, 2006

How Do I Copyright My Pictures?
posted July 16, 2006

At the July (Saturday 7/15/06) HAL-PC Clear Lake Digital Photography SIG meeting the question of Copyrighting photographs came up.

Simply stated, a copyright attaches the moment the shutter is released. That is, you automatically have the legal copyright to pictures you take without doing anything.

US Copyright law does not require you add a copyright notice to your photograph for it to be protectable, but notice prevents an infringer from claiming he/she did not know the work was copyrighted. Notice consists of the symbol © (or the word “Copyright” or the abbreviation “Copr.”), the year of first publication and the owner’s name.

Though registration with the US Copyright Office isn’t required, it provides certain rights. For example, you must register a copyright before you can sue an infringer. So, if someone uses your photograph without your permission, before you can ask a court to stop him you must register the photograph. You can do this after your copyright is infringed, however it will delay you getting relief.

Registration costs about $45 and can include many photographs, not just one.

This article contains additional information on the subject http://photography.about.com/cs/businessmatters/ht/ht_Copyright.htm

Disclaimer: As with almost all law, and particularly Federal laws; copyright law can be quite complex with many exceptions to generalizations. This article is intended to be a quick thumbnail of a thumbnail. Entire books are written on this topic. If you have a serious need to copyright your photographs you will need to do some extensive reading. You can start here.