[beholder3]

If you used a different lens on the K1 or moved the camera forward so that the final images for two cameras were identical from a compostion stand point the K1 should be better.

Is this correct?

The different lens would need to be a lens with same aperture and x1.5 focal length at same shutter speed. Say 300/4 replaced by 450/4 (that is effectively a 500/4, currently Canon new version at $9000).
If it only was "equivalent" aperture you'd cancel out any advantages.

"Moving forward" effectively means "no cropping at all required" in your scenario and thus less need for enlargement, so yes, obviously less perceived noise.

[jpzk]

should be provided by a real professional, an optical engineer or something like that

...maybe falconeye would give a little more info regarding this debate?
falconeye - View Profile - PentaxForums.com
JP

[enoeske]

But the context is irrelevant to the original post and not correct in that context.

Would the high ISO performance be better with a crop sensor lens on the K1 compared to the K5iis?

The original post specifically (and only) asks if performance of the K-1 sensor in cropped mode be better than the K-5iis. We have answered that question.

[jsherman999]

Given the pixel density is similar between K5iis and K1:

If the image is cropped to APS-C size, the ISO performance will be identical or very close to each other. No FF advantage here.

If the lens is able to cover the full circle ( no crop here), the noise is still similar but due to 36mp density when you shrink the size of shot to the same taken by k5ii, you will get one stop advantage.

This ^ and Adam's answer and a few others are correct - if you shoot an aps-c lens on FF which auto-crops to aps-c dimensions, and then you display the images the same size, you've just given up the noise advantage that came from shooting on the larger sensor. You're basically shooting with a larger, more expensive aps-c camera then

It may still be a little less noisy because the K1 sensor is (presumably) newer tech, but it's not going to be as much of an advantage as shooting a FF lens with the same FOV on the K1 would give.

For example:

FF lens : 50mm f/1.8 shot on FF
aps-c lens: 35mm f/1.8 shot on aps-c

Gives you the same FOV, and about 1.3 stops better noise performance (and less DOF) in the FF combo, maybe a bit more or less noise depending on how good that new sensor is.

But shoot that same 35mm f/1.8 on FF and auto-crop, and the image will be about the same in FOV, DOF, noise and DR as if you had just shot the 35 on the aps-c in the first place.

(In the case of the K1 vs. K5, the resolution of the crop would be about the same too, since the pixel density is the same.)

[christiandre]

If you take a photo of a perching bird that fills the frame on the K5IIs and then take the same photo with the same lens with the K1 and crop that image to show the same amount of the bird and print the images to the same size are you not basically using the same amount of light that fell on that section of the image that is in the cropped part of the K1 as fell on the K5IIs and having the same number of pixels that recorded the image. So there should be no benefit of using a full frame sensor over a APS-C sensor of the same quality.

... but, but, but

Bird is on a tree in front of you, and you take a picture :

- with a K1, image parameters is : ISO 3200 + 1/1500s (light picture, nothing to fix)
with dslr 16Mp crop mode, or after, with photoshop taking a 16Mp portion of the bird

or

- with a K5IIs, native 16Mp full image at ISO 200 + 1/400s (darker image, less sharp...)

You have finallly two 16Mp images, but not the same quality ?
IMO, K1 crop image could be better, no ?
It's hard to believe, sorry

[beholder3]

enoeske in post #9 and HavelokV in post #14 explained it already perfectly in a nice short way and answered the question.
Everything beyond that is "noise" and seems only to confuse people more, the longer the discussion goes.

If you really want to mess things up big time, add some idiots with rambling "physics" "explanations" and this is going to be another neverending thread with no value left for anyone.

[redrockcoulee]

... but, but, but

Bird is on a tree in front of you, and you take a picture :

- with a K1, image parameters is : ISO 3200 + 1/1500s (light picture, nothing to fix)
with dslr 16Mp crop mode, or after, with photoshop taking a 16Mp portion of the bird

or

- with a K5IIs, native 16Mp full image at ISO 200 + 1/400s (darker image, less sharp...)

You have finallly two 16Mp images, but not the same quality ?
IMO, K1 crop image could be better, no ?
It's hard to believe, sorry

If using the same lens and ending up with the exact same image size on the sensors why would I shoot them at different ISO and shutter speeds.

---------- Post added 03-16-16 at 12:21 PM ----------

The different lens would need to be a lens with same aperture and x1.5 focal length at same shutter speed. Say 300/4 replaced by 450/4 (that is effectively a 500/4, currently Canon new version at $9000).
If it only was "equivalent" aperture you'd cancel out any advantages.

"Moving forward" effectively means "no cropping at all required" in your scenario and thus less need for enlargement, so yes, obviously less perceived noise.

The reason I gave for using the same lens or moving the camera forward was to be using the full sensor on the K1 and filling the frame which you could not do with using the same lens and the same spot with the two cameras. In that case of using the same lens on each camera and wishing to use the same compostion you are using the same sensor size, in other words none of this total light gathering stuff would matter, you are using a APS-C slice of the FF sensor and only that part of it. Why should having more sensor outside the image area give one a better image?

[christiandre]

If using the same lens and ending up with the exact same image size on the sensors why would I shoot them at different ISO and shutter speeds.

---------- Post added 03-16-16 at 12:21 PM ----------

because k1 can go higher than K5IIs in ISO levels ? And so, i can increase again shutter speed, maybe for a better IQ ?
... read on this forum, 1600 ISO K1 = 6400 on K5 or something like that

So my question remains

same size, same lens, same natural light, same bird, same tree OK
don't understand why the K1 can't give a better image than the other, even with the same size same lens etc ? Sorry

[enoeske]

because k1 can go higher than K5IIs in ISO levels ? And so, i can increase again shutter speed, maybe for a better IQ ?
... read on this forum, 1600 ISO K1 = 6400 on K5 or something like that

So my question remains

same size, same lens, same natural light, same bird, same tree OK
don't understand why the K1 can't give a better image than the other, even with the same size same lens etc ? Sorry

It can and will provide better image quality when you use the whole sensor. When you use an APS-C lens on it, it doesn't use the whole sensor. So, you won't get better, only equal, image quality in that case.

[pete-tarmigan]

so... for wildlife or birding, compared with an K5IIs, the loss of range on a K-1 can't be offset by any other advantages...

...unless the autofocus tracking and speed improvements of the K-1 over the K-3ii are substantial.

[christiandre]

OK, thanks guy
So... two solutions for me
waiting for a k-mount 150-600 tamron or sigma + K1 (D810 with tamy @600mm = amazing results sometimes)
or waiting for the next Kxx APS-C with some K1 tech (AF, DR...)
now, just keep my K5IIs / 150-450 for little birds.... cheers

[2351HD]

+1

And you might add:
you will see less dynamic range.
you will see less DoF
you will easier see AF deviations
you will likely see more CA

How on earth will you see less depth of field. It's the same lens, same aperture on the same sensor. It won't change one bit.

Where you people get this rubbish from is beyond me.

This is out of control.

[enoeske]

How on earth will you see less depth of field. It's the same lens, same aperture on the same sensor. It won't change one bit.

Where you people get this rubbish from is beyond me.

This is out of control.

He's assuming that your subject to distance ratio (perspective) will change with the switch from FF to APS-C as you will have to stand farther back for the same framing with APS-C.

[2351HD]

No he is not. We are talking about cropping a picture, that is all. Apsc sensor vs FF with same lens, same settings, same distance, but cropping the FF to match.

[beholder3]

How on earth will you see less depth of field. It's the same lens, same aperture on the same sensor. It won't change one bit.

Where you people get this rubbish from is beyond me.

This is out of control.

Rubbish:

1. Defocus behind/in front of the focal plane leads to a point being imaged as a blurry disk ("circle of confusion").
2. What is considered the DoF is the extent of the image where points are either points or at least very small disks. And this "very small" has to be less than the defined "maximum circle of confusion" or in easy words "what you consider sharp / in focus".
3. So DoF is basically defined by the "disks" under a certain size limit
4. Now you crop and print the crop to the original frame size, you thus enlarge the crop.
5. Thus you enlarge every part of the image, including your details, which consists of points and different size disks.
6. And now an area previously consisting of acceptably small disks (you did consider them sharp/in focus/within the DoF) consist of disks too large to be acceptable. They now are blurred. Out of focus. Out of DoF. Now a smaller part of the image seems to be within the DoF.

Test:

Take a portrait with a fast 50/1.4 wide open, where you think the full face is still within the DoF. Crop it down heavily and look at the crop in the same size print/screen as the original picture. Don't you now see more blurry stuff and don't you now perceive more of the image as blurry and out of focus and thus have a smaller in focus area = less DoF?

This is all about enlarging things. Here: enlarging the non-sharpness of areas not perfectly in the focus plane.