Film Vs Digital, how much Resolution ?

By ralph

Long time film based photographers that have been entertaining the notion of branching into digital cameras often get a bit intimidated by the huge number of choices. First there�s the range of prices, models and makes, and then the question of just how much resolution, expressed in mega pixels, that they would need.

About 10 years ago Kodak pretty much set the aim point for pro use at around the 6 mega pixels that their $28,000 DCS 460 ( later 560, etc.) delivered. This was thought of as somewhat equivalent to the quality of film and has been a sort of �gold standard� ever since.

When the affordable �prosumer� cameras first appeared they had clearly too little resolution � in fact it took a couple years just to get to the first one Mega pixel, and yet those cameras have gradually clawed their way up to a good 5 MPs. At the same time competition brought the pro, 6 MP cameras down to the top end of the prices of the prosumer cameras (say $1500).

And yet the Popular Photography Magazine test on the new Kodak DCS Pro14n showed that it finally took 13.5 mega pixels of information to equal the actual detail of a 35mm negative � and in fact they chose a 400 speed negative film for comparison, admitting that a slower film like Provia 100f would still beat the new camera.

Yet watching the comments of professional photographers on internet forums I�ve learned that many of them and their customers are more than pleased by the results from 5 and 6 mega pixel cameras. They even claim they get knockout 20x30 in. prints from them. In fact a very few years ago Canon and Nikon were selling just 2+ MP cameras and showing prints of that size which had unbelievable quality.

So what�s going on here? Do we need 2 or 3, or up to 13 mega pixels for good quality?

The three big factors we look for to achieve highest quality are grain, sharpness and resolution (fine details) � um � wait, isn�t that last item redundant.? Isn�t sharpness and resolution the same thing? Well, not quite. It seems that digital images can separate these factors in surprising ways. Images of just a few mega pixels can be easily sharpened to an extraordinary degree in many stages of production from the camera or scanner to the computer software. Sharpness becomes almost independent of size or resolution. Secondly, since most photographers like grain about as much as dandelions in the lawn, much of the push to larger formats is to get that crystal smooth look that goes with minimal enlargement. Ah! but there is no grain in digital images even with fairly low resolution images (except for noise that results from excessively high ISO speeds),. The smooth textured pixels especially shine in those even, wide open tones like blue skies, which used to betray the slightest grain when shot on film . I recently got around to printing a striking shot of a blue morpho butterfly that I bypassed for years because I only had a 1.3 mega pixel image (it was scanned for e-mail use and then the original became unavailable). I was amazed how good the 5x7 looked so I went on to an 8x10 which was also quite impressive (but the edges were getting a bit wavy). I also scanned a similar image to top resolution but it made a less satisfying print because the original film grain was resolved and it detracted from the image .

It even seems hard to see any shortfall in the fine detail from those less than 14 MP cameras. Could it be because we rarely realize the full potential of film? Or is it because those fine, sharp edges so fully meet our idea of how an image should look?

At any rate that leaves us with a fairly wide range of choices on the mega pixel scale. From 3+ MPs you should get good 11x14s or more, with 4 or 5 you can push up to and past 16x20s. The 6 or more MP cameras should meet most normal needs even beyond 16x20s.

The serious amateurs and pros are of co
se, drawn to the 6+ MP, Nikon and Canon SLR (single lens reflex) bodied cameras that offer familiar handling and viewing (and of course that includes the widely adopted by professionals, Nikon D1x at 5.5 MBs). They start about $2000 and go up to about $7000 for the Canon EOS 1Ds, which seems to be king of the hill for overall superiority. Despite having �only 11 MPs�, it gets the edge over the 13.5 mega pixel Kodak because of the low-noise clarity of the image. The Fuji S2 is also considered close to the �big� Canon in the rank of quality. One of the nagging shortcomings of the pro type SLRs till recently has been the fact that the image chips were smaller than the standard 35mm film gate, effectively making lenses seem longer. That�s just fine for telephoto fans but a real downer for those who need maximum wide angle. The two new biggies, the Kodak and Canon have laid that problem to rest with full frame image chips.

It seems that the prosumer cameras up to 5 mega pixels also offer very good value, in fact many have some extraordinary virtues that even the pro SLRs can�t match.

For starters, while many photographers are turned off by the non-interchangeable zoom lenses, these lenses keep the camera interior sealed against accumulations of dust and dirt. Many hard working pros (who change their lenses often, sometimes in less than ideal conditions) find that their CCD ( charge coupled device) image chips actually draw dirt to their surfaces. The backs no longer swing open (no film) so the CCDs are hard to clean. Canned air is the usual remedy though it�s considered unsafe. Unfortunately those zooms in the prosumer cameras are pretty weak on the wide end , generally only going down to (the equivalent of) 35mm. The 28 mm zoom (equiv) in the Minolta Dimage 7 is a notable exception.

Secondly, and here�s a two edged sword, the prosumer cameras generally have pretty extreme depth of field. That�s because their actual �normal� focal length is around 9 or 10 mm, since the image chips are so tiny., and of course, the shorter the focal length the greater the depth. With my �entry into digital� Coolpix 995 camera (with a 3.3 MP chip), I found myself shooting groups of people in an interior at f2.6 (wide open) at 1/30 second and set to 400 ISO. This usually means soft and murky images but I was surprised to get bright, colorful and wire sharp 8x10s and the sharp zone went a couple yards behind the subjects. This extreme depth even shows up in the very close macro range. In a hothouse I noticed a small desert cactus with tiny orange blossoms, about 3/8 inch across surrounded by tiny red buds. The buds were about � inch lower than the blossom and hopelessly out of focus with my 105mm macro on 35mm. With the Coolpix, which has an astonishing macro range that auto focuses down to a field smaller than a 35mm frame (about one inch away) I couldn�t clearly see the focus looking at the viewscreen at arms length, so I just fired away. When I reviewed the image I was surprised at the sharpness of both flower and buds. The extreme macro is another feature of many (but not all) prosumer cameras. The downside of course, is that you just can�t deliberately throw things out of focus. The background to the average flower shots will be only a tad soft � still very distracting. In contrast, those pro SLR digital cameras, probably using lenses you already own, show no differences in depth of field to film cameras.

Incidentally I find I get many steady shots at 1/30 sec. despite the wispy lightness of the camera. I guess the lack of shutter and mirror motions helps. In fact there is no shutter. Electronics simply select the chosen interval from the continuously illuminated image chip.

That leads to an even more startling virtue of cameras like the Nikon Coolpix. They flash synch at any speed from 8 sec to 1/2000 sec. Absolutely no pro SLR can do that. In fact many of the pro SLRs have even given up the 1/250 sec. speed that was becoming the norm in recent years. Lea
f shut
ter cameras have always been considered the best for flash work since they also synch at top speeds � but their top speeds are rarely higher than 1/400 or 1/500 sec. At higher shutter speeds you can do outdoor sun and synch pictures at hand hold- able speeds for people pictures. Higher flash synch speeds also increase the distance at which you can have effective fill flash. I just tried this by shooting a flash fill shot of the whole house, in the sun, from mid street, at 1/1000 sec and f4.8 with a small Sunpak flash on a side bracket. (the 1/2000 was no better indicating that the flash duration itself was about 1/1000 sec or more). Many prosumer cameras share this trait with the Coolpix, though the otherwise excellent Olympus E-10 and E-20 top out at 1/640 sec because of an odd scanning pattern.

I almost define the �prosumer� class of cameras as those that need viewfinders because they are not SLRs. The LCD viewscreens help extend their usefulness, in fact using those screens is the only way to shoot in the macro range. Of course the main virtue of the LCDs is the instant review of your picture. One feature lacking in the Coolpix is dedicated flash but with the LCD it�s easy to shoot tests and arrive at a good macro exposure fairly quickly. To test that I moved into a closeup of the face of my watch (about 1 � inches away), swung the small sunpak flash around to the side (to clear the front of the lens), set it at 1/16 th power and stopped down to f 10 (the limit) in manual and did a test shot. Amazingly, the image was well exposed and sharp as a tack.

Framing and checking focus in the tiny LCD is actually a poor substitute for viewing in a SLR finder (it�s pretty dim in daylight) but some cameras go beyond that. The Minolta Dimage 7 series and the new Nikon Coolpix 5700 internalize the LCD and create a similar effect to reflex viewing. The view is not as sharp as a film SLR but it�s almost as useful. By the way the Olympus E-10 and E-20 are the only true SLR�s in the prosumer class. Incidentally the Coolpix 995 is no longer made but the Coolpix 4500 is the almost identical upgrade with a 4 MP chip and a lower price (about $600 to $700).

Of course, the prosumer cameras do have their downside. First there�s that peculiar delay between when you push the button and the actual taking of the image which makes them unusable for sports and other moving situations. In the Coolpix it�s about a half second. Some are even slower though others like the Olympus E 20 are comparable to film cameras. Then there�s the menu maze. Sure they can do a million things, like change the ISO or white balance, but you may have to juggle through several menus to find out how (and always keep the manual handy).

Now for a last gee whiz. Many digital cameras filter out the infrared light for various reasons like controlling color balance and avoiding meter problems, but some manage without the filtration. When those cameras are fitted out with the almost opaque infrared filters they can produce excellent B&W infrared images. One of them is the Minolta Dimage 7 and I was at a seminar where the photographer, using that camera, described the almost magic effect of putting the dark filter over the lens then looking in the enclosed LCD to see an ethereal world of beyond-human-vision infrared.