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11-07-2022, 05:11 AM   #1
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K-3iii cropping function

Has anyone used the cropping function when taking images with the K 3iii. I am thinking of the scenario of wildlife, where you want that extra reach from your long lens.
Did you find this function useful and does this function degrade the image quality compared to the full frame equivalent image.
Looking forward to your comments.

Update - I have taken some sample images in RAW and confirm some of the replies below, that for RAW files, the image size in MB for the 'standard' frame size and the cropped frame size remain pretty much the same. Also examining the images at 100% and above, there is no reduction in image quality when using the cropped function, when viewing the RAW files.
I am very impressed with this and gives the equivalent option of a pseudo teleconverter. Another innovative Pentax function. The only negative aspect I see is that the reduction in JPG file size reduces the maximum print size, if printed from this format.
For an image comparison, file sizes are for the same subject are shown below:
Standard frame
RAW DNG 35.2 MB
TIFF conversion 73.1 MB
JPG conversion 15.7 MB

1.3 x Crop Frame
RAW DNG 33.7 MB
TIFF conversion 43.1 MB
JPG conversion 10.6 MB


Last edited by Robert N; 11-08-2022 at 05:40 AM. Reason: Further testing of cropping function
11-07-2022, 06:01 AM   #2
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QuoteOriginally posted by Robert N Quote
Has anyone used the cropping function when taking images with the K 3iii. I am thinking of the scenario of wildlife, where you want that extra reach from your long lens.
Did you find this function useful and does this function degrade the image quality compared to the full frame equivalent image.
Looking forward to your comments.
I don't have the K3 III, but I understand the function is similar to the K1 and K1 II crop mode.

It wont give you "extra reach" per se. Your subject's (say a bird) size on the sensor and the number of pixels that record it is the same. The automatic crop that the mode provides gives you nothing in image quality or magnification that you could not do yourself either in the cameras playback cropping menu, or in post processing the image yourself. If you don't pp your images and use the jpegs straight out of the camera then I can see it can be a useful mode. The mode displays a cropped border in the viewfinder to aid framing.

The other advantage it may confer is that the camera may process the images and empty the buffer quicker, useful if you are shooting in continuous high mode.
11-07-2022, 07:54 AM - 1 Like   #3
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QuoteOriginally posted by pschlute Quote
I don't have the K3 III, but I understand the function is similar to the K1 and K1 II crop mode.
Not exactly, IMO. The K-1 has two sensor readout zones. One FF readout that covers the whole sensor and provides an additional square crop defined by a square region in the raw file, and a second sensor readout zone covering the APS-C area. The second one yields to faster continuous mode.

I also don‘t own a K-3 mk iii. My understanding is that this camera doesn‘t offer two sensor readout areas. So the crop mode isn‘t faster and covers the original full APS-C size at raw file level. Opening a crop mode raw file with software that doesn‘t recognise the crop region should show the full size APS-C image.

Last edited by acoufap; 11-07-2022 at 08:04 AM.
11-07-2022, 09:00 AM - 1 Like   #4
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I've used it a number of times. It's a 1.3x crop (the same that is used when shooting 4k video). It's handy if you don't have the HD 1.4x teleconverter. Recorded pixels = just under 16 MP.

11-07-2022, 09:05 AM   #5
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QuoteOriginally posted by Kobie Quote
I've used it a number of times. It's a 1.3x crop (the same that is used when shooting 4k video). It's handy if you don't have the HD 1.4x teleconverter. Recorded pixels = just under 16 MP.
Megabytes of the raw files same as non-crop raw files?
11-07-2022, 09:43 AM   #6
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QuoteOriginally posted by acoufap Quote
Megabytes of the raw files same as non-crop raw files?
I'll double check in a bit. But I recall it being much smaller for the crop raw vs full raw.
11-07-2022, 10:51 AM   #7
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QuoteOriginally posted by acoufap Quote
Megabytes of the raw files same as non-crop raw files?
I'm pretty sure crop mode with mk III does really crop it. There is no up-scaling done.
However, the images from mk III are so good, I feel I'm not losing much by using it.

11-07-2022, 11:09 AM   #8
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QuoteOriginally posted by Lloyd_Christmas Quote
I'm pretty sure crop mode with mk III does really crop it. There is no up-scaling done.
However, the images from mk III are so good, I feel I'm not losing much by using it.
Guesswork doesn't help.

If the Pentax K3-iii would have a real second readout for crop mode this would be indicated in the manual by a second raw size. But there only is one RAW format mentioned: (26M:6192x4128).

An owner of the camera can test it - and that's pretty easy: install the camera on a tripod and shoot the static scenery with raw files in full and crop mode, then compare sizes of both raw files. If the the file size of the crop mode file is significantly smaller than the full APS-C size raw, then crop mode also means crop at raw level, otherwise ... . Takes only a few minutes.

Last edited by acoufap; 11-07-2022 at 11:14 AM.
11-07-2022, 11:14 AM   #9
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The crop size remains the same in raw but gets converted when processed as a jpeg.
1) Standard Jpeg
2) Standard Raw
3) Crop mode Jpeg
4) Crop mode Raw
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11-07-2022, 11:16 AM - 1 Like   #10
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QuoteOriginally posted by Kobie Quote
The crop size remains the same in raw but gets converted when processed as a jpeg.
Many thanks for posting this clear comparison.
11-07-2022, 02:23 PM   #11
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i used a lot 1.3 crop mode on k3 iii , even customize playback button to crop . all crop mode pictures has same DNG file size as APSC , only difference when you convert DNG to JPG .
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