Film vs. digital:
I've started shooting 4x5 instead of digital APS-C and right now I'm going for a "f64" look, mostly with longish lenses for the subject matter (primarily landscape). This means some serious stopping down. Sometimes. On a 300mm lens, f45 and f64 are sometimes necessary...
Since 4x5 is a little more expensive per shot ($6 vs free) than digital, I'm wondering if, with the next generation of dSLRs, 4x5 will offer no advantages--for my purposes.
Here's the hypothetical that bugs me:
Let's say I'm shooting the same scene with a Canon 7D and a 45mm tilt/shift lens as I'm shooting with a 300mm lens on 4x5. It's a pretty deep focus scene so I stop down to f64 with the 300mm lens.
On 4x5 I'm diffraction limited at 25lp/mm. And 25lp/mm*2 lines/line pair*120mm (width of 4x5 film)=6000 lines of resolution. Thankfully most film can resolve this just fine with acceptable contrast. Unfortunately, since diffraction also softens lower frequency detail than the absolute extinction limit indicates, these are 6000 fuzzy lines of resolution. This is being generous. I've read repeatedly that in real world situations no one ever gets above 25lp/mm, except maybe in the very center, at any stop in 4x5.
On the 7D, to get the same depth of field, I need to shoot at around f11. Now I'm diffraction limited at 141 lp/mm. And 141lp/mm*2 lines/line pair*23mm (width of 7d sensor)=6486. The difference between this and the figure for 4x5 film is just due to me using imprecise equivalents. It's really the same in both cases. Anyhow, since the 7D has a 5184 pixel wide sensor, we'd get 5184 semi-fuzzy pixels in this case.
The resolution of both images should be closer to identical.
With this generation of digital cameras, this problem only arises in extreme situations (300mm at f64, which is used but not often in landscape photography). It's still kind of humbling to think that an APS-C sized sensor matches 4x5 in some real-world cases, though.
Megapixel counts are still increasing at huge rates. Will the quality advantage of 4x5 over dSLRs still exist in four years? Before you cry foul, there are some lenses which are diffraction limited at f4-f5.6 and live view allows you to implement tilt/shift with per-pixel precision.
It seems digital sensors and modern lenses are getting so good that lens diffraction, not sensor size, will be the limiting factor in coming years, and instead of medium and large format we'll be dealing with full frame and APS-C digital virtually exclusively as "professional" formats.
But my non-inflammatory question is this: it seems there's a given resolution limit for a photo, irrespective of format, based solely on FOV and DOF....so why are my eyes so much sharper than a 1:1 print? Maybe they really aren't.
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