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[OM] How many megapixels? (Was Rethinking the Olydak)

Subject: [OM] How many megapixels? (Was Rethinking the Olydak)
From: dreammoose <dreammoose@xxxxxxxxx>
Date: Sat, 05 Oct 2002 00:32:31 -0700
I, and others, I believe, have said before that a 2mp image from a good digital camera is capable of producing a really excellent 8x10 print. A lot of the bad things you hear about digital quality are the result of assumptions and resulting experiences and like you had. A good part of the problem is simply learning curve. If you were getting really lousy results from 35mm and a wet darkroom, you would know from the general experience/knowledge all photographers share as a group that some part of the process was failing, and likely have some idea where to look. This isn't the case yet with digital and there is a lot of misunderstanding and misinformation floating around.

If you read the interchange between me and Joe Gwinn, you know some of the issues of grain (granularity) aliasing in digital scanning. It appears that, with certain films, upgrading from 2700 to 4000 dpi could actually give worse results! There is, however, another technical issue that can greatly affect the quality of digital prints from digital files.

When I got my Epson 1280 and then my 2700 dpi scanner, I was puzzled by my first results. I made a nice 8x10 from about half of an APS negative. Grain was visible if I looked for it, but it was a good looking print and equivalent to about an 18x27" print from a full 35mm frame! Then I made a print from a different frame with very little cropping and it came out with a strange granular look, almost like some kind of subtle solarization mixed with lots of graininess. I fussed and puzzled a bit before coming to the idea that it was probably a software problem. Thinking it through, I realized that arbitrarily sizing of a digital image could easily lead to strange results. If the dpi of the image at the set print size is not an even divisor of the dpi of the printer, the printer driver has to interpolate. Lets say it has to print 11 pixels from each 7 or 9 pixels in the source. There is no mathematical way to do that and maintain the integrity of the image! The software will do it's best, but the result will inevitably be poor. On the other hand, converting 10 to 5 pixels or 3 to 9, etc. isn't a big problem to do.

So I tried letting the size of the image decide the actual size of the print. I made a chart of dpis that are even divisors of the 1400 dpi resolution of the printer and only printed at those dpis. So an 8x10 may turn out to be 7.7x10.2, depending on how it is cropped, etc. The immediate result was uniformly good prints, so I've stuck to this procedure. When downsampling scanned images for the web or other purposes, I also only downsample by simple integer divisors of the image resolution, never to arbitrary sizes. I'm not claiming that this is the specific solution to your problem, only that pixel resampling and interpolation is a crucial part of the digital darkroom that needs to be understood and addressed in order to get good results.

I got a call from my older son a few days ago. He just got a new iMac with iPhoto software and wanted to know why the pictures he was printing from his 3+mp camera mostly looked so much worse than the ones I made, not only from 35mm, but from my 2.1mp camera, and why they were so variable, some looking almost decent and others quite bad. When I asked, sure enough, he was cropping and then arbitrarily sizing to 4x6 (or whatever).

I know some of us would like the digital darkroom to get us away from all that complex stuff with choice of developer, dilution, times, yada, yada, yada. Maybe that time will come, but for now we have to learn how to use the new tools to get the results we want. I think software needs to get smarter and warn us when we are making choices that will degrade the image. My print driver should say "Printing this image at 5x7" will not give good photo reproduction. Print at 5.17 x 6.93 inches?" or some such.

I've made really good looking 8x10 prints from cropped digital images of around 1000x1200 dpi, or about 1.2mp. That means to me that 5mp is good for 16x20 prints, as our E-10 and E-20 users have said. Why ask for cameras with huge output files if they aren't needed for the desired end result? An Olydak 4/3 with 5-7 mp and a line of good quality interchangeable lenses would make me quite happy. Even better, how about greater dynamic range, greater sensitivity and less noise in the sensors, rather than piling on the megapixels? Those kind of improvements would be much more useful to me for improving my ability to make the images I want.

Moose

Chuck Norcutt wrote:

My first impression of the Olydak was negative based on the perceived low resolution of the current 5 megapixel Kodak 4/3 sensor. I have heard some of you E-10 and E-20 users praise the enlargement quality of your 4 and 5 megapixel sensors but it didn't seem like it could be so great. After all, here I am scanning film at 9 megapixels on my Acer Scanwit and an 8x10" is about as large as I can go since the "grain" begins to show much beyond that. I've placed "grain" in quotes since it's not clear to me that's actually what I'm recording.

For the past several months I have owned a Nikon CoolPix 800 which I bought refurbished from B&H for $199. It's a 2 megapixel camera which I bought just to get my feet wet in digital and to be able to make quick snapshots and web quality shots. I've always considered that I needed to print at 300 dpi for good quality output and this camera's 1200x1600 resolution should (in my mind) only support a 3x4" print.

Well, a couple of weeks ago I decided to try a 5x7" print which required dropping the resolution to 225 dpi. I was amazed since it still looked pretty good. I never considered going beyond that until this morning when I tried an 8x10" print at 150 dpi. Amazing! This 2 megapixel image still looks very good even at 8x10". So, now it seems to me that a 5 or 6 megapixel sensor probably is capable of handling any size enlargements I'm likely to need.

And now the last point. I assumed that the Olydak would be built with Kodak's current 5 megapixel sensor which happens to have a 4/3 size ratio. However, after visiting their site this morning are reading what they had to say about their deal with Olympus it's not at all clear that this is the sensor to be used. Their official statement says only that details of the 4/3 sensor will be released in the future. That's a pretty strong implication that the sensor to be used is not the current one. Perhaps that sensor will have an even higher resolution.



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