Photography and Art

Friday, October 31, 2008

Law of Diminishing Returns and the Canon 50d

Last week, I had the pleasure of attending an art auction fundraiser for Art City Toronto, a store-front art drop-in centre for under-privileged kids in Toronto. I donated a couple of works to the silent auction and I'm delighted to report that an 18x12 framed print of my Phonehenge image sold for nearly $400. Here's the image:

It was fascinating to watch people in the silent auction as they looked at the artwork. For this particular image, a lot of people did a double-take when they noticed the old English phone booths (the photo was taken on a farm in southern Ontario in Canada). Many people walked up close to the photo to look at the details and, I'm happy to say, at 18x12, the details hold up just fine. The photo is quite sharp at that size.

Nowadays, I take most of my photos with a full-frame 12.8 megapixel camera, a Canon 5d, but the Phonehenge image was taken with an 8 megapixel APS-C camera, the Canon 20d. With the recent advent of the 50d and the 5d mk II, I've been starting to think about upgrading the 20d. In fact, I've placed the 20d on permanent loan to my son while I cogitate about an upgrade.

You can imagine my interest level when DPreview published an in-depth review of the Canon 50d. After reading the review and looking at the resolution stats and the RAW noise levels of the new camera, I must admit that I now have misgivings. With the current state of the art in sensor silicon, it looks like the sweet spot for APS-C sensors is around 10-12 megapixels. Any larger and noise levels start to increase. Not only that, but system (i.e. camera and lens) resolution becomes a matter of diminishing returns. Look at the following tables extracted from DPReview:

Camera Measurement
Canon EOS 50D Horizontal LPH 2250 2700
Vertical LPH 2200 2700
Nikon D300 Horizontal LPH 2200 2600
Vertical LPH 2100 2600
Pentax K20D Horizontal LPH 2250 * 2300
Vertical LPH 2250 * 2500
Sony DSLR-A700 Horizontal LPH * 2200 2900
Vertical LPH 2100 2800
Canon EOS 40D Horizontal LPH 2100 2300
Vertical LPH 1800 2300

Camera Measurement
Canon EOS 30D Horizontal LPH 1850 2100
Vertical LPH 1650 2100
Nikon D200 Horizontal LPH 2100 2250
Vertical LPH 1700 2200
Canon EOS 5D Horizontal LPH 2300 2500
Vertical LPH 2000 2500
Canon EOS 20D Horizontal LPH 1850 2100
Vertical LPH 1650 2100

Looking at the absolute resolution, moving from 8 MP (20d) to 10 MP (40d) to 15 MP (50d) results in a gain in horizontal resolution from 1850 to 2100 to 2250. If this was correlated to the number of megapixels, you would expect 1850 to 2336 to 3608. Clearly, there is something (e.g. lens resolution) hitting the wall that is preventing these new sensors from delivering on their promise. Not only that, but noise seems to go up beyond 10-12 megapixels, so the extra resolution may be getting obliterated by extra noise.

All other things (i.e. automatic sensor cleaning, larger LCD, LiveView) aside, is it worth paying $1,500 to get an uplift of 22% in resolution at the expense of more noise? Consider this in the context mentioned above, where an 18x12 image produced at a resolution of 1850 lines holds up to a room full of people examining the image up close.

I'm thinking that I might wait for the 40d to come down in price and buy a good used model instead.

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