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04-13-2020, 08:29 AM   #1
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can you "uncrop" older lenses on APS-C (pentax KP) camera

I've just bought myself a Pentax KP (absolute steal so couldn't say no). Up until now I've been using film cameras (Pentax LX and KM yes i know it's 2020 but it's how i got back in photography) and as the lenses (all M and A series primes) were designed for them what i saw was what i got, well what i saw was what i got 2-3 weeks later when i finally got round to developing them.

Now I know about crop factor but I'm finding it a difficult transition to what i'm seeing in my viewfinder to what's actually coming out in the pictures. Is there any way to crop your viewfinder so that what you see is a little closer to what you take or is there a way to uncrop the picture, or is this just something i'm going to have to learn to work around?

I'm sure there will be many helpful hints and tips on these forums about that area but i'm struggling to find the info.

04-13-2020, 08:34 AM - 1 Like   #2
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The viewfinder on an APS-C camera is cropped. A 100% viewfinder on a KP is showing you 100% of what the sensor "sees". By way of comparison the KM viewfinder was 93% (of 36x24 vs 23.5x15.6 for the KP). The KP viewfinder is also .95x magnification while the KM is .87x.

Last edited by boriscleto; 04-13-2020 at 08:43 AM.
04-13-2020, 08:34 AM   #3
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You should be seeing in the viewfinder what is on the sensor. In fact, most viewfinders, by design, show slightly less (typically 5-10% less) than what is captured on the sensor.
I don't know of any camera, either film or digital, that shows more in the viewfinder than is captured.
04-13-2020, 08:39 AM   #4
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I think the KP has a 100 percent pentaprism viewfinder. What you see in it should be what your sensor sees (give or take a tiny bit).

04-13-2020, 08:42 AM - 1 Like   #5
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The photos are not actually cropped, the sensor itself is smaller or "cropped" so you are getting the full picture the camera captured. The angle of view is different, a 50mm lens on the KP would have the coverage as a 75mm lens on 35mm film camera. Looking through the viewfinder you should be seeing what would be captured, a full frame lens on a crop sensor camera is not going to give a wider field of view.
04-13-2020, 08:55 AM   #6
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Ok thanks, maybe it's my mind playing tricks on me or i'm remembering my film pictures differently and i'm too used to the "numbers" to those and just not used to the angle of view. My first digital camera after years of film, so it just all "feels" different to what i'm used to.
04-13-2020, 09:09 AM - 1 Like   #7
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Pretty much What-You-See-Is-What-You-Get with the KP viewfinder. Film cameras typically had a built-in cutoff on the viewfinder to simulate the frame cutoff you'd get with slide mounts on the 35mm frame.

And the other oddity is the 35mm frame has an aspect ratio of 3:2 (36× 24mm) while 10 × 8 in prints have a ratio of 5:4 (1.5 vs 1.25). Why don't viewfinders have markings for this cutoff?

04-13-2020, 09:27 AM - 1 Like   #8
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QuoteOriginally posted by lifeincolour Quote
Ok thanks, maybe it's my mind playing tricks on me or i'm remembering my film pictures differently and i'm too used to the "numbers" to those and just not used to the angle of view. My first digital camera after years of film, so it just all "feels" different to what i'm used to.
Yep...the best viewfinders with a 35mm film SLR are like looking through a window, while those on an APS-C dSLR are a little like looking into a box with a screen at the end. Your KP is about as good as it gets from APS-C as far as percent coverage and magnification (100%, 0.95x).

FWIW...If you were moving from a medium format film SLR to 35mm, you would feel much the same way.


Steve
04-13-2020, 10:33 AM   #9
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QuoteOriginally posted by stevebrot Quote
Yep...the best viewfinders with a 35mm film SLR are like looking through a window, while those on an APS-C dSLR are a little like looking into a box with a screen at the end. Your KP is about as good as it gets from APS-C as far as percent coverage and magnification (100%, 0.95x).

FWIW...If you were moving from a medium format film SLR to 35mm, you would feel much the same way.


Steve
That's exactly it, it just feels wrong (not wrong as in bad, wrong as in i'm just not used to it) the looking through a box really is a great description for it.
04-13-2020, 11:53 AM - 1 Like   #10
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The "crop-factor" crap-factor strikes again.
04-13-2020, 12:46 PM   #11
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Ok. So I thought I understood crop factor. I did not. I’ve swapped the same lenses between my LX and my KP and I now think I do. Something new to learn.
04-13-2020, 12:52 PM - 1 Like   #12
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QuoteOriginally posted by lifeincolour Quote
Ok thanks, maybe it's my mind playing tricks on me or i'm remembering my film pictures differently and i'm too used to the "numbers" to those and just not used to the angle of view. My first digital camera after years of film, so it just all "feels" different to what i'm used to.
It took me a while to learn how to 'think' in APS-c terms when I transitioned from 35mm film. It comes as second nature now. You certainly picked a great camera for your first DSLR. You'll love it once you get used to it.
04-13-2020, 12:55 PM - 4 Likes   #13
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QuoteOriginally posted by lifeincolour Quote
Ok. So I thought I understood crop factor. I did not. I’ve swapped the same lenses between my LX and my KP and I now think I do. Something new to learn.
I'd like to offer some advice regarding crop factor.

You can dwell on it
You can bang your head against a concrete wall
you can go take pictures.

The first two options have largely the same result; but the third is much more enjoyable and satisfying.
04-13-2020, 01:11 PM - 9 Likes   #14
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QuoteOriginally posted by lifeincolour Quote
Ok. So I thought I understood crop factor. I did not. I’ve swapped the same lenses between my LX and my KP and I now think I do. Something new to learn.
Its easy! The basics are:
  • Going wide is harder than on 35mm
  • Going distant is easier
  • Macro is the same except that for a given reproduction ratio (e.g. 1:1) there is less subject in the frame
  • Infinity is still infinity
  • Minimum focus distance remains the same
  • >60mm is long
  • 200mm is the new 300mm
  • 50mm to 58mm is portrait length
  • 28mm to 35mm is normal
  • 24mm and below is wide
  • 16mm and below is ultra-wide

Corollary...If anyone mentions the word "equivalence" or suggests that apertures or anything other than focal length be multiplied by crop factor, react as if the comment is a matter of politics or religion.


Steve

Last edited by stevebrot; 04-13-2020 at 02:50 PM.
04-13-2020, 02:46 PM - 3 Likes   #15
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QuoteOriginally posted by stevebrot Quote
Going wide is harder than on 35mm
Going distant is easier
These were the things that struck me most when I got my first (APS-C) DSLR after many years with an SLR.

Most people coming to APS-C with a set of vintage lenses will need to consider getting extra coverage at the wide end - ie lenses with focal lengths that previously seemed unimaginably wide. There are numerous threads discussing the options. Even if you prefer primes, don't rule out zooms - they are often a good affordable way into wide coverage and there are some very high-quality modern zooms in K-mount.

Congratulations on the KP, @lifeincolour - it's an amazingly capable camera. I'd suggest getting the KP ebook written by the late lamented Yvon Bourque - it's full of useful practical information.
QuoteOriginally posted by stevebrot Quote
If anyone mentions the word "e*****lence" or suggests that apertures or anything other than focal length be multiplied by crop factor, react as if the comment is a matter of politics or religion.
Mind your language Steve. ;-)

Last edited by Des; 04-13-2020 at 02:51 PM.
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