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08-18-2015, 04:21 PM   #16
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QuoteOriginally posted by jsherman999 Quote
DR is affected, as is noise when you crop and enlarge the crop to the same display dimensions.
True, but I'm not doing that. Just cropping so no change to DR.

QuoteOriginally posted by jsherman999 Quote
hopefully Pentax will offer a selectable crop amount - like 2:3 aspect ratio, square, or something like 1.2x crop (in addition to 1.5x, which is aps-c.)
Hopefully. I think Nikon has FF, 1.2x, and 1.5x on their cameras. I would like to see that on Pentax. Ideally an 'Auto' mode that reads the lens chip, an 'OFF' mode that doesn't crop no matter what and 1.2x and 1.5x crops.

08-18-2015, 09:44 PM - 1 Like   #17
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QuoteOriginally posted by jatrax Quote
True, but I'm not doing that. Just cropping so no change to DR.
But after you crop, you either view it on your screen or print, correct? Are you viewing/printing everything 1.5x smaller after you crop?

You don't need to actively 'enlarge' anything - your printer driver does it, your display does it. Enlarging after crop is the default action - you have to try *not* to do it.
.

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Hopefully. I think Nikon has FF, 1.2x, and 1.5x on their cameras. I would like to see that on Pentax. Ideally an 'Auto' mode that reads the lens chip, an 'OFF' mode that doesn't crop no matter what and 1.2x and 1.5x crops.
Yep. Nikon also has 'square' and 3:2, and despite the fact that you can just do that in post it is nice to have and can save time/effort sometimes.
08-18-2015, 10:55 PM   #18
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how is dynamic range affected by cropping or enlarging an image?
08-19-2015, 08:44 AM   #19
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QuoteOriginally posted by AtitG Quote
how is dynamic range affected by cropping or enlarging an image?
The same way noise is affected in the resulting image. I think you probably (through experience) know that cropping (and enlarging) reduces IQ - resolution is affected, and noise becomes more visible - image DR is affected as well.

Here's a very easy to understand and well-described summary: Dynamic range D800 FX vs DX

Here's Bill Claff's measurements of PDR from raw files, 800 cropped (DX) and uncropped (FX):


08-19-2015, 11:39 AM   #20
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The linear sloping part of the graph is fairly self-explanatory. I am assuming the plateau is due to the inability of DR to improve beyond (or rather below) base ISO? Also, my understanding is that this is for crop and uncrop modes on the same sensor?
08-19-2015, 02:09 PM   #21
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QuoteOriginally posted by pathdoc Quote
The linear sloping part of the graph is fairly self-explanatory. I am assuming the plateau is due to the inability of DR to improve beyond (or rather below) base ISO? Also, my understanding is that this is for crop and uncrop modes on the same sensor?
Yes, D800e(DX) is in-camera raw 'crop mode' (1.5x crop, aps-in other words.)

When Pentax introduces FF, if you shoot an aps-c lens in 'crop mode' on it, you will see reduced DR and more noise in the final image, at the same display sizes. However, I'm betting that crop mode will match or slightly exceed the K5II in IQ, so it's not like your crop-mode images will suck - they will still be very good, you'll just be giving up the FF 'advantage' in those particular images.

In other words, you'll be be able to take your time replacing your aps-c lenses, or just keep and enjoy them, shooting one body in dual modes.
08-19-2015, 02:33 PM   #22
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QuoteOriginally posted by jsherman999 Quote
But after you crop, you either view it on your screen or print, correct? Are you viewing/printing everything 1.5x smaller after you crop?
How many people view or print at 100%?
08-19-2015, 07:53 PM   #23
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QuoteOriginally posted by jsherman999 Quote
But after you crop, you either view it on your screen or print, correct? Are you viewing/printing everything 1.5x smaller after you crop?

You don't need to actively 'enlarge' anything - your printer driver does it, your display does it. Enlarging after crop is the default action - you have to try *not* to do it.
.



Yep. Nikon also has 'square' and 3:2, and despite the fact that you can just do that in post it is nice to have and can save time/effort sometimes.
Enlarging is not the default on anything I own. If I crop to 1000x2000 that is what prints. Because if I allowed it to be enlarged the image would degrade. And I don't want that.

Basically I think we agree that cropping and enlarging will degrade the image. But I am not enlarging k-3 images to 42mp. And I would not be enlarging a cropped 42mp image either. I accept that shooting a FF 42mp image with a crop lens is going to result in a smaller image.

08-19-2015, 09:02 PM - 1 Like   #24
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QuoteOriginally posted by mohb Quote
How many people view or print at 100%?
You don't view or print at 100%, you view or print at the same size as before you cropped. When you have two 8x10 prints, for example, one a crop of the other, the cropped image has been enlarged more compared to the uncropped.

The only way around this is to print the uncropped (FF) at 8x10 and the cropped (aps-c, 1.5x) at 5x7 - keeping it un-enlarged compared to the original. YOu then have the same DR in both - but 1.5x smaller dimensions as the trade-off. (I think most people would think that's usually a dumb trade-off and just accept a little more noise and less DR.)



---------- Post added 08-19-15 at 10:16 PM ----------

QuoteOriginally posted by jatrax Quote
Enlarging is not the default on anything I own.
It pretty much is the default if you ever display a crop of an image at the same dimensions as the original image.

The crop is enlarged compared to the original, even if both are not even printed/displayed at native resolution, and the relative degradation follows Bill Claff's curve - or the difference in the curves shown between say the D7000 and D800 on DxOmark's 8MP normalized 'print' tabs. (Also, this describes what the OP of this thread was asking about, and what people usually do with 'crop mode' - they don't throw out all their 8x10 paper and move to 5x7 for their crop shooting in a desperate attempt to try to keep DR the same in that little cropped image - they display/print both at the same size, determined by screen viewing window or desired frame size.)

There's no free lunch here. You don't get to crop a FF image and keep all the advantages of a larger sensor, and one of the advantages you give up is DR.

EDIT: By the way, here's a nice thread on this subject and it discusses how to derive the expected DR hit based on crop factor: D800 1.2x crop DR loss

.

Last edited by jsherman999; 08-19-2015 at 09:51 PM.
08-20-2015, 04:52 AM - 1 Like   #25
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QuoteOriginally posted by jatrax Quote
Enlarging is not the default on anything I own. If I crop to 1000x2000 that is what prints. Because if I allowed it to be enlarged the image would degrade. And I don't want that.
Do you keep them same print size? i.e. if you're printing a series of 12x18's from your k-3, but you've cropped one of your k-3 images down to 3000x4500 pixels, do you print this one at 9x13.5 or at 12x18? If 12x18, you've "enlarged" it more than the photos you haven't cropped. If 9x13.5, you'll end up with a bunch of photos at odd sizes, and I don't think this is the way most people operate.
08-20-2015, 06:58 AM   #26
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In a related vein, I have noticed that using the DX crop mode on a D610 also has an impact on the metering. On the several times I tried it, I had lots of poor exposures - usually over-exposures.

Perhaps because somewhere along the line, the camera was expecting to meter across a full frame, but had to deliver an image that was 'cut' from a smaller part of the frame. Or Nikon just hasn't get their firmware right for DX crop mode on D600/D610.
08-21-2015, 12:48 AM   #27
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Thank you jshermann for the reply. I thought that it was the tonal range that is affected by enlarging. But I'm certainly far from being an expert when it comes to this topic.
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