The Fallacy of Judging Image Quality Online
Leica M9 with 90mm f/2 Summicron @ ISO 500
I alternately chuckle and get steamed up when I read someone on a web forum either condemn or praise a camera or lens based on a web images. This is utter nonsense. What can one possibly tell from a 100ppi image on a screen, except of course how it looks on a screen at 100ppi? What screen, was it calibrated, and how long ago, and what are the viewing conditions, and.....
Now, if judging a camera or lens' performance by means an image on-screen is your idea of a good time – well, fine. But, except for the Flickr crowd that's not what fine photography is about – at least it isn't for me.
Fine Art photography has always been about the print. In the recent world of digital imaging and the Internet there is a new dimension to viewing images though, and that's fine. You just have to look at this web site to understand that I am firmly ensconced in this environment, and am no Luddite on the matter.
But if we are going to judge photographs and the equipment used to produce them based on online viewing of 800 pixel images then one is simply wasting ones time and money. Might as well get a nice little pocket cam and be done with it, for all the difference it makes.
There's more. Web images are in sRGB which means that their colour gamut is highly compressed. Many photographers are now using monitors that can display Adobe RGB when provided wide gamut files, and most new printers can print colour even beyond that. A web image becomes very poor reflection of what a good print's colour palette may look like.
Web images are also JPGs, which means that they are highly compressed, and image data has been thrown away to achieve this compression. Some photographers who post their images online take the effort to prepare minimally compressed images, but most simply automate the process and end up with small files that display quickly but which are highly lossy.
But what about looking at images at 100% on-screen? There one can see the differences – right? Well, yes, one can see the difference of how they look on-screen at 100% magnification. The fact that this has little to nothing to do with how an image will appear in a print seems to escape many people. This applies to judging high ISO noise, resolution and more.
Especially ISO quality, when cameras of different resolution are compared. High resolution cameras can have lower high ISO noise than a lower resolution one, because when similar sized prints are made the lower magnification needed plays a significant role in allowing the noise to be reduced in visibility. By the same token, a camera with lower resolution will likely appear noisier when it is enlarged to match a larger one – because what noise there is will be enlarged along with the image. This is one of the reason's that high resolution CCD-based medium format cameras, though they may appear to be noisier than DSLRs in 100% on-screen crops at any given high ISO, are actually less noisy in display prints.
Bottom line – it's only in a photographer's final print that one can really make these determinations, not with 100% on-screen enlargements, which may indeed show the opposite of what is actually the case.
I would feel less riled up about this if it wasn't for the fact that I encounter people almost daily that come to my gallery and say, "I can't believe how different your images look in prints to how they look on your web site." It's almost as if these folks are reading from the same script. Talking to other photographers who both show their work online and then in large prints, I hear the same thing; how people can't believe the differences. In fact I know quite a few widely exhibited fine art photographers who refuse to show their images online because they feel that this misrepresents how their work should be seen.
Whether your photography is ultimately destined for web display, or as prints, isn't the point. Both can be appropriate venues. But please, please, stop judging the technical quality of photographic equipment by looking at small web images. And, while 100% crops can be helpful in comparing certain technical aspects of image quality, this usually bears little real-world relationship to how a photograph will appear in a print. In my experience its rare that the pixel peeping that the online image analysis that many people love to do bears any real-world relationship to how an artist's image will appear in a final display print
Photography is a pursuit that involves esthetics as well as technology. The later serves the former, and it is only when seen in the context of an image's final form of presentation that it is possible to evaluate the technology that helped produce it.
Leica M9 with Tri-Elmar @ 50mm. ISO 160