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01-20-2017, 02:10 PM   #1
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When using an APS-C lens on a K-1, is the only performance difference resolution?

If you used a lens for APS-C cameras in the crop mode on the K-1, do you still get the same Color Depth, Dynamic Range and ISO performance that you get with it in the full-frame mode? I am assuming the only difference is that it is a 15 megapixel image versus 36.


Thanks.

01-20-2017, 02:15 PM   #2
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Per pixel, yes. Overall, no.
01-20-2017, 02:17 PM   #3
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Yes. You are simply using a smaller area of the sensor.
01-20-2017, 02:21 PM   #4
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QuoteOriginally posted by ozturert Quote
Per pixel, yes. Overall, no.
SO how is the Color Depth, DR and ISO changed?


Thanks.

01-20-2017, 02:22 PM   #5
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QuoteOriginally posted by ozturert Quote
Overall, no.
Can you elaborate. If I take a picture in full frame mode and crop it to the same size as aps-c I have two identical images.
01-20-2017, 02:24 PM - 1 Like   #6
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QuoteOriginally posted by bladerunner6 Quote
SO how is the Color Depth, DR and ISO changed?
Remember, the reason equivalists say APSC is so much inferior is because they insist on forcing the APSC frame to fit the FF (in terms of FoV and DoF) and only compare after this. And that gives APSC a massive disadvantage and makes it look worse by comparison.
If you use APSC mode and use that photo as a 15MP photo, then it will look the same as FF, with edges cut off. IF you blow up that 15MP to 36MP, then the image will look worse than one taken directly at full 36MP, obviously. IF you take that 15MP image and change its ISO and aperture to get the same DoF and FoV as the FF mode, then it will look worse.

tl;dr: Use APSC if you wish, don't worry about it. Feel free to check threads that test DA and other crop lenses on FF, as sometimes you can get away with something more than APSC (like APSH). If you have a nice 36MP sensor, it makes sense that you use it as much as you can
01-20-2017, 02:30 PM   #7
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QuoteOriginally posted by Na Horuk Quote
Remember, the reason equivalists say APSC is so much inferior is because they insist on forcing the APSC frame to fit the FF (in terms of FoV and DoF) and only compare after this. And that gives APSC a massive disadvantage and makes it look worse by comparison.
If you use APSC mode and use that photo as a 15MP photo, then it will look the same as FF, with edges cut off. IF you blow up that 15MP to 36MP, then the image will look worse than one taken directly at full 36MP
So if I take a photo in the crop mode on the a K-1 using a Sigma 10-20, it will give me a 15megapixel image with the field of view of a 15-30 used in the FF mode?


The Color Depth, DR and ISO should be the same though?
01-20-2017, 02:36 PM - 1 Like   #8
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QuoteOriginally posted by bladerunner6 Quote
The Color Depth, DR and ISO should be the same though?
Nothing changes except the amount of pixels recorded if you are in crop mode. If you place the camera in FF mode then the camera will record the full 36mp but the image will vignette. You can then crop out the vignette and you will get an image that uses all of the lens image circle of that particular lens. It might be 15mp, or 18mp, or 20mp or 28mp or whatever. Each lens will be different. But in crop mode the camera restricts the image to the 15mp approximate.

But nothing else changes as far as the quality of the pixels produced. What you are asking about are camera functions, not lens functions. Those things would be the same with a FF lens, a APS-C lens or plastic pin hole lens. The lens is just a chunk of glass in front of the sensor.

01-20-2017, 02:40 PM   #9
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I don't think the Sigma 10-20mm is as high quality as the DFA 15-30mm, so you might notice a difference in contrast and sharpness (and bokeh, flare resistance, colors, CA, possibly even T stop brightness). And the FoV migh't appear different due to things like distortion, and the measurements of the focal length being slightly off. Often a lens is not exactly the same FoV that is written on it. For example, if you buy 50mm lenses from different manufacturers, they will not be exactly the same. But very close! Close enough for nobody to really care.
But the DR of the recorded data, and noise levels, are camera sensor properties, not lens properties, so these will depend on camera.

But you can do your own test. Grab a zoom lens and take photo at two focal lengths, and use FF mode and then APSC mode. (shoot raw) Open both in Photoshop or Lightroom or whatever you use to PP the photos. Now you can easily compare
01-20-2017, 02:57 PM - 2 Likes   #10
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QuoteOriginally posted by pschlute Quote
Can you elaborate. If I take a picture in full frame mode and crop it to the same size as aps-c I have two identical images.
Exactly. "Physics. Not just a suggestion. Its a law."
01-20-2017, 03:08 PM   #11
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QuoteOriginally posted by bladerunner6 Quote
The Color Depth, DR and ISO should be the same though?
Per-pixel, characteristics are of course the same, but looking at he whole picture, the above properties are different. See https://www.pentaxforums.com/forums/169-pentax-full-frame/318574-does-larger-...ml#post3602078 for a statistical explanation and way more discussion on the topic than you'd likely want in the rest of the thread.
01-20-2017, 03:08 PM   #12
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This is where the "total light" argument may be invoked.

In theory depending on what side of this camp you fall on - either the total light the entire sensor area used has will matter or it will not. In this model you might use the full area to resample things to the size you might need and this total light is supposed to be important in this way. The other side will say - same size pixels with the same cpu and noise reduction etc. leads to the same results but fewer pixels. Essentially saying that if there was a updated K-5 with the same electronics as the K-1 then the output of it and the K-1 crop would be very very similar.

Me I'm not sure what to think. I lean towards the latter view - that the pixels size, type, etc. and the electronics drive this not the total light.
01-20-2017, 03:10 PM   #13
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QuoteOriginally posted by bladerunner6 Quote
So if I take a photo in the crop mode on the a K-1 using a Sigma 10-20, it will give me a 15megapixel image with the field of view of a 15-30 used in the FF mode?


The Color Depth, DR and ISO should be the same though?
I have both lenses, and a K-1. I could make a a test, but how do you want to measure Color Depth, DR and ISO ?
I guess that you would do these measurements on RAW files, but how do you downsample the 36MP image taken with the 15-30 to a 15MP RAW that could be compared with the 15MP APS-crop RAW? Or can you simulate the downsampling after having done the measurements on the original RAW?

In theory, if you take one picture with the 10-20 at f/5.6 and ISO 100, and the other with the 15-30 at f/8 and ISO 200, the results (for 15MP images, and in terms of color depth, dynamic range and noise) should be similar.
01-20-2017, 03:18 PM   #14
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QuoteOriginally posted by Ptitboul Quote
In theory, if you take one picture with the 10-20 at f/5.6 and ISO 100, and the other with the 15-30 at f/8 and ISO 200, the results (in terms of color depth, dynamic range and noise) sould be similar.
This is where the confusion comes in. How do you compare the photos, and what is being used as the basis.
Both of those photos will have the same dng standard with the same bit depth and same amount of noise per pixel. But once you start enlarging the APSC shot, or downsampling the FF shot, or you try to get the exact same DoF and FoV.. this is where the comparison method itself can introduce a lot of bias. This is why I say "dont worry about it" because a lot of people get obsessive over some numbers and try to make them fit in some way. When in reality, an average audience viewer would have a hard time telling apart a K-5IIs photo from a K-1 in ASPC mode. Especially if you are shooting in normal light conditions with decent PP. Its only photographers who obsess over every bit of depth and every little speck of noise. Things like printing type or different computer monitors or different PP software can introduce bigger differences in the final image.
01-21-2017, 06:42 PM - 2 Likes   #15
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QuoteOriginally posted by Na Horuk Quote
When in reality, an average audience viewer would have a hard time telling apart a K-5IIs photo from a K-1 in ASPC mode. Especially if you are shooting in normal light conditions with decent PP.
That is absolutely correct from my personal experience with the K1 and my old K5IIs. If circumstances are identical, the results are too as far as the naked eye can see.

The huge difference is that the K1 will focus instantly and accurate in situations the K5IIs would not. It makes a ton of difference in the number of keepers. Low light is a whole new experience with the K1 as well as shooting wildlife in brushy situations where the K5IIs tended to hunt for the focus subject.

I love the Crop Mode for my Bigma, and it is a FF lens but the Crop Mode works best for me. In effect, I have two cameras in one...FF and APS-C! Gotta love it!

One of my favorite K1 shots in Crop Mode.


One of my favorite K5IIs shots.


Both are superb cameras!

Regards!
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