Pentax 560mm lens now listed on Adorama...any takers!

Started Nov 5, 2012 | Discussions thread
Alex Sarbu Veteran Member • Posts: 7,594
Re: Resolution, diffraction limits, long lens on Q etc...

miles green wrote:

Alex Sarbu wrote:

I doubt many would be happy if Pentax were to switch to an inferior format. You are overestimating the "benefits" - a simple crop can "fix" such "issues.

Agreed, as I elaborate below.

Pentax can simply keep up with the ever increasing sensor resolution (and they obviously will).

The ever increasing sensor resolution will end when the best prime lens don't reach their peak center resolution before diffraction limits their performance. Then there will be no point in increasing sensor resolution. We're just a few years away with APS-C:

With current 16 mpx sensors, resolution is visibly affected by diffraction at f/11.

With a 30 megapixel aps-c sensor, diffraction will be visible at f/8*

With a 60 megapixel aps-c sensor, diffraction will be visible at f/5.6*

With a 120 megapixel aps-c sensor, diffraction will be visible at f/4*

* = when pixel peeping. or better when visually exploring a large print. I'm not talking about circles of confusion or viewing distance. You don't get a 80 mpx camera for "normal" viewing distance.

Can an aps-c lens resolve 30 mpx at f/8? I think so. 60 mpx at f/5.6? Maybe the very best. How about 120 mpx at f/4? I seriously doubt it!

Well, a good lens can easily resolve 16MP @ f/5.6; I guess doubling the linear resolution, for a total of 64MP, is feasible. But thinking of the precision involved, including focus... it's more and more difficult to actually use the extra resolution, outside labs.

Anyway, with Bayer arrays some oversampling would still bring benefits; but we'd have to give up looking at per pixel sharpness for the bigger picture (pun intended )

Given these physical constraints, I think that aps-c cameras will never exceed 60 mpx, FF 35mm will stop by 140 mpx, FF 645 could theoretically reach 420 mpx etc... (btw: P645 != D800)

I hope by then we'll see more imaginative solutions, e.g. replacing the Bayer array.

Alex

 Alex Sarbu's gear list:Alex Sarbu's gear list
Pentax K-5 IIs Pentax K-1 Pentax smc DA 21mm F3.2 AL Limited Pentax smc DA 70mm F2.4 AL Limited Pentax smc DA 35mm F2.8 Macro Limited +6 more
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