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Equivalent digital resolution to film

Paul Heagen , Apr 06, 2010; 08:08 a.m.

My old Canon EOS elan II film camera has now lost its mind and needs to be put down. I am shopping for a digital to replace it (and hopefully be able to use my AF lenses?) but am not clear on what resolution of digital is equivalent to 200 or 400 ASA film in 35mm.

I heard that my film camera had a resolution that was equal to a 15Megapixel camera, which i know I cannot afford.
Is there any way to equate the effective resolutions of film and digital? There are plenty of used 8Mpx cameras out there that would work for me if it is not a step back in picture quality.

Thanks for any help.


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Matt Laur , Apr 06, 2010; 08:12 a.m.

How large do you print?

Mike Stemberg , Apr 06, 2010; 08:34 a.m.

Just by chance I found myself at this page earlier today, which has points that may help you in your thinking:

link:Digital SLR vs Film Scans

Mike Earussi , Apr 06, 2010; 08:36 a.m.

Depends on who's test you use. According to Popular Photography even the best Sony 24 mp camera only just comes close to ISO 100 film in 35mm format in absolute resolution. But other tests have shown that a good 12 mp camera can produce images as good as a 645 MF camera. For example, here are a few of the tests:
http://www.kenrockwell.com/tech/2008-09-new.htm (under Sept 20)

and there are many more.

Matt Needham , Apr 06, 2010; 08:59 a.m.

Is there any way to equate the effective resolutions of film and digital?

An excellent way is to compare prints side by side. Assuming good shooting technique and processing I think 8mp APS easily matches 35mm at low ISOs, and as the ISO goes up is much cleaner looking than 35mm.

David W. Griffin , Apr 06, 2010; 09:19 a.m.

The limiting factor is probably your scanner, especially these days with film scanners on the decline. My old scanner was about the equivalent of a 6MP DSLR for my eyes. File sizes aside, my better Nikon Coolscan V ED (no longer sold) seems to give me images that seem pretty equivalent to a 10MP camera or so. I think my Canon 5D (mk I) probably has more useable resolution. I suspect any modern DSLR including the Rebels would probably satisfy you as far as image quality is concerned.

The truth is that I was pretty amazed at what my first DSLR could do (Konica Minolta 5D 6.1MP). I dont' think you have to buy a really expensive Canon to reach the same conclusion.

Craig Big , Apr 06, 2010; 09:27 a.m.

I have just recently seen excellent reviews that have indicated that the resolution of 35mm film is undefineable by digital standards. It could conceivably continue to yield additional detail up to 100MP, but this cannot be proven yet with today's technology. This has so much to do with technique, that many of the online reviews are misleading. If a reviewer "proves" that film is only 8MP, he has usually used a cheap film scanner or some other simple mistake. The best reviews I've seen involve printing an enlargement from the film first, up to 20 times the size of the negative. Then they'll scan the print under high resolution, like 4000dpi or greater. When comparing this to a digital image from a 24MP camera, the film can easily be shown to give more detail under close inspection. Just how much more will have to wait to be proven. Until we see a 35mm digital camera with a 100MP sensor, we still won't know the comparative limits of film resolution. Here's the review I recently found: http://www.imx.nl/photo/Film/page169/page169.html I have seen other similar reviews before, but failed to bookmark them at the time. Of course, this still doesn't address the issue of, "Does this even matter?" We've all seen by now that an 8MP digital camera can make comparable prints to 35mm film, that hold up under scrutiny surprisingly well, at least until you get really, really close, or magnify really, really large. So the common-sense answer is that it just doesn't matter which system you use from a resolution standpoint. Personally, I would shoot for at least a 12MP camera from the latest generation of digitals. This has the best chance of impressing you, rather than disappointing you.

Robert Gussin , Apr 06, 2010; 09:28 a.m.

If you are happy with film, buy a used film camera from a reliable dealer. Even a cheap, old film rebel will work with your lenses. And some of the last are pretty nice! Even a used Elan II is less expensive than a digital camera.

Alan Johnson , Apr 06, 2010; 09:37 a.m.

The number of line-pairs per millimeter a film will resolve may be in this table:
To get from line-pairs per millimeter to pixel equivalent for 35mm film, multiply ( lppm x2 x24 xlppm x2 x36 ).
It's an approximation that ignores a lot but gives a rough idea. 63 lppm gives about 14 m-pixels.Higher than this even a good lens may be limiting.

Danny Low , Apr 06, 2010; 12:35 p.m.

I went through this calculation years ago when deciding when to convert to digital. The limiting factor is not film resolution but lens resolution. With the best film around, you can expect lens resolution to top out around 80 lp/mm. This is under perfect laboratory shooting situations. In real life, you will get less due to various real life complications such as camera shake. I calculated that 16MP was good enough to be 35mm equivalent.

However an even lower limit was paper and screen resolution. Unlike slide film, you never look directly at a digital image. Like negative film you have to "print" it either to paper or a computer screen and the resolutions on those mediums is far less than what the lens or film can record. The practical reality is 5MP will give you an 8x10 print that most people will say is better than film. The reason is digital images have no grain and the lack of grain makes digital images look much better. Digital images have noise but that is not as noticeable as grain.

So there are factors with digital that make it better than film that has nothing to do with resolution. Color rendition is another. Different films were known for their different looks due to the way they recorded color. Afga films were known for their pastel colors while Fuji films had a neon brightness. A friend who was a painter found that some films could not accurately record certain colors when the paint was acrylic but worked fine with oil paints. Digital tends to be far better in recording colors accurately.

I also found that the digital darkroom was far superior to the wet darkroom. I could manipulate my photos in ways that were not possible with film while sitting in a well lit room and breathing the aroma of fine coffee rather than developing chemicals. With digital, you want to do darkroom work as it is so easy. Most editing programs have automated the most common functions such as red eye removal.

However the best reason to go digital is the cost. You can shoot your digital photos, download then to a computer, clear the memory and you are ready to shoot again. Total out of pocket cost is zero. With film, you have to process the film and buy replacement rolls. That averaged about $25 a roll when I last shot film. As a result I paid for the cost of my digital camera and lens in just one year from the savings in film processing and purchases.


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