[Cannikin]

I corrected my earlier mistake. The 1.5x factor is on the DIAGONAL, not the height|width. So an APS-C 16mpx sensor with the same pixel density scaled-up to FF would be 32mpx. APS-C is very close to 135/HF (half-frame) or 24x18mm, half the area of 135/FF at 36x24mm.

Um, all linear dimensions are scaled the same. If the aspect ratio is the same, then 1.5x the diagonal means 1.5x both the height and width.

Proof:
Pythagorean theorem: A^2 + B^2 = C^2 (where A/B are height/width and C is diagonal)

C = sqrt(A^2 + B^2)

(1.5C)^2 = (1.5^2)C^2 = (1.5^2)(A^2 + B^2) = (1.5^2)A^2 + (1.5^2)B^2

therefore:

(1.5C)^2 = (1.5A)^2 + (1.5B)^2


Just for reference the K-5's APS-C sensor is 23.7 x 15.7mm (roughly 24x16, a scaling of 1.5 in every dimension). 24x18 isn't even 3:2.

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Last edited by Cannikin; 06-18-2012 at 10:04 PM.

[Williunck]

You lose nothing of the sort. Focal length is independent of sensor size.
You GAIN angle of view, but the central crop is exactly the same image you would have had with APS-C.

Yeah, but who has time to crop every photo - with the smaller sensor it feels like a bigger lens, and with resolution now its better than ever. If bigger is better, why isn't everyone shooting with the Pentax 645? and even this seems odd to me, but most of the new mirrorless systems are all based on an even smaller sensor.

[Mohawk]

Therefore:

Digital APS-C (k-5) = 23.70mm x 15.70mm = 372.09 mm2 = 3.72cm2
Digital 135 (say, theoretical k-3) = 35.55mm x 23.55mm = 837.20 mm2 = 8.37cm2, scaled exactly 1.5x for each linear dimension of k-5 sensor

Equivalent k-3 sensor at the same pixel density of a k-5's 16.28 MP sensor = 16.28/3.72 * 8.37 = 36.63 MP

Uncropped k-5 @ 16.28MP (16.08 MP effective) = 4928 x 3264 pixels at max. image size
Uncropped k-3 @ 36.63 (36.19 MP effective) = 7392 x 4896 pixels at max image size

[Williunck]

Uncropped k-3 @ 36.63 (36.19 MP effective) = 7392 x 4896 pixels at max image size

OK just to be devils advocate - who needs a 36 MP image size? Maybe only a handful of professionals making huge prints at full resolution, but certainly no one shooting for magazines or newpapers. I mean you can get poster size prints and even larger that are very sharp from a 16 MP sensor. I can see where 18-24 MP sensors are uselful, but 36, and when is it going to stop? 5 years ago I read an artical where they compared a 16 MP image to the resolution of a medium format negative and it was almost (not quite) but almost on par. I don't blame people for wanting to use their full frame glass though, that is the best argument i can think of.

[ElJamoquio]

I like 36 MP because it has almost zero disadvantages compared to APS-C - I can still crop to a k-5 image.

I also like 24 MP because the files are slightly smaller. Both are ok with me.

[builttospill]

To me FF means using my FA Limiteds the way they were meant to be used... and thats reason enough for me to go FF

Exactly. They were meant to be used with a camera having a large, bright optical viewfinder. Oh wait, were you talking about FOV?

[builttospill]

I think 36mp would be ridiculous. It could also hurt sales of the 645D. I don't have a need for any more than 24mp, especially since my 10mp K10D has produced beautiful photos for bulletin/billboard ads.

[Barbarosa]

Less MPs will do that most of the lenses are still usable. It is bigger pixel on sensor if is FF and less MPs so lenses with lover resolving resolution are perfectly fine on sensor like that . Most of ppl intend to use older lenses so 24 MP would be much better than 36.

[Alizarine]

If bigger is better, why isn't everyone shooting with the Pentax 645?

Maybe because it's $10,000 brand new... and around $7,000 lowest, prolly, second-hand. Well, the 645D, at least.

[ogl]

Therefore:

Digital APS-C (k-5) = 23.70mm x 15.70mm = 372.09 mm2 = 3.72cm2
Digital 135 (say, theoretical k-3) = 35.55mm x 23.55mm = 837.20 mm2 = 8.37cm2, scaled exactly 1.5x for each linear dimension of k-5 sensor

Equivalent k-3 sensor at the same pixel density of a k-5's 16.28 MP sensor = 16.28/3.72 * 8.37 = 36.63 MP

Uncropped k-5 @ 16.28MP (16.08 MP effective) = 4928 x 3264 pixels at max. image size
Uncropped k-3 @ 36.63 (36.19 MP effective) = 7392 x 4896 pixels at max image size

It seems to me 24 MP is sweet spot. I see at K-5 that the best apertures moved a bit close to wide-opened.
I really see that my FA*24 has the best apertures at f4-6.3 at K-5 and f5.6-8 at K200D.
24 MP is very good for FF. New sensor with not much MP could be the best mix of resolution/noise/DR. Remove AA filter and it will shine.

[gtl]

Lol. I could do with both.

Exactly. They were meant to be used with a camera having a large, bright optical viewfinder. Oh wait, were you talking about FOV?

[fast50]

OK just to be devils advocate - who needs a 36 MP image size?

Manufacturers of RAM and hard discs

[Rondec]

OK just to be devils advocate - who needs a 36 MP image size? Maybe only a handful of professionals making huge prints at full resolution, but certainly no one shooting for magazines or newpapers. I mean you can get poster size prints and even larger that are very sharp from a 16 MP sensor. I can see where 18-24 MP sensors are uselful, but 36, and when is it going to stop? 5 years ago I read an artical where they compared a 16 MP image to the resolution of a medium format negative and it was almost (not quite) but almost on par. I don't blame people for wanting to use their full frame glass though, that is the best argument i can think of.

Well, I think the issue is that at 36 megapixels, full frame takes away nearly any benefit of APS-C. Any "extra length" APS-C gives to your lenses is based on increased pixel density, not on the cropped format. The only downside is that it slows down frame rate and fills buffers faster -- really, the D800 has an amazing sensor.

Really, megapixels isn't as big a deal right now as things like iso and dynamic range, but down sampling a high megapixel image often gives better results than an image shot at lower resolution in the first place.

[ElJamoquio]

Maybe because it's $10,000 brand new... and around $7,000 lowest, prolly, second-hand. Well, the 645D, at least.

Went to $6k after the D800 came out.

[Kunzite]

Well, for a while Samsung was rebadging Pentax cameras. Not sure whether that refutes or reinforces the not a "real camera" company claim.

Please, don't forgot about the smilie; I wasn't seriously claiming that.
Unlike when they were rebadging Pentax DSLRs (real cameras, just not Samsung's ), they seems to put some effort in their NX system. Strangely, though, they have almost as many gadget MILC things cameras as lenses. Electronic giant corporation line of thinking?