Crop Size Compared to Resolution Ratio

So I have a question on how you guys crop your photos, either for print or web. This will help with another question that I might post regarding lens comparisons.

When you export an image either for print or for web do you match the resolution to be at least a 1:1 ratio to the crop?

For instance... my Canon 5D Mark iii has a max resolution of 5760 x 3840. I want to print an image at a physical size of 5" x 7" from my 5DMiii to cropped aspect ratio of 5:7(just to keep it simple), usually I print to a resolution of 300 PPI. So the image I need to export from LR or PS will have to have a minimum resolution of 1500 x 2100 pixels. This being the case I will not crop the original image to anything less than 1500 x 2100 so as to keep a least a 1:1 ratio. If I crop any tighter the cropped image will have to be "blown up" to meet my 300 PPI resolution, which depending on how much it is blown up would create some pixelation.

Pretty much what I am saying is that if I am planning on creating an image with a short edge of 1000px I will make sure that I have at least 1000px cropped on that side.

Do you guys do anything similar?

I realize that when exporting for posting here on this forum or the web that image size doesn't matter so much since many browsers resize images larger than they normally would be, particularly on my Apple MBP Retina display. When I export for Instagram I keep the horizontal edge of the image to 1080px, so that allows me to crop much tighter than I would be able to if printing for a resolution 300PPI. When exporting for wallpaper for my 13" MBP I keep the short edge to 1600px, so a little less to crop than 1080px.

It seems to me that when looking at the lens sample forum, some of the images are cropped beyond at 1:1 ratio caused some pixelation and softness when viewed online.

Any thoughts?

I will usually crop the image for composition, but accepting that I will need to adjust the aspect ratio to match my chosen print size. If I am truly stuck with an aspect ratio, then I know I will have to use a custom cut mat when framing it, or just trim it to the required aspect ratio. I don't particularly worry about the number of pixels at this point though, although it will always be a concern. If I don't have a lot of pixels to play with I may generate an image that I know will only be used online in small sizes.

When exporting a file from Lr for printing then I will do the necessary resampling myself as part of the export process. Usually in that situation I will export the image so that it matches exactly the requirements of the printing device. The amount of resizing that an image can take will usually depend on the content of the image. For example I have some images that started out at about 1200 Px on the long edge that when printed at 16×12", requiring a file of 4800×3600 Px from Lr produces excellent prints. There are other images that I would never try that on.

A lot also depends on the viewing conditions; a 16"×12" viewed from 20" will be visually identical to a 16 yard by 12 yard image viewed from 20 yards, even though it is a 36× linear enlargement. If the viewer cannot get any closer than 20 yards for the big image you won't need to worry about any additional image data.

Of course ideally you will only need to crop the image minimally for aspect ratio for the print size you are going to use. You will normally be able to work with lenses with a suitable focal length so that you can fill the frame with your desired subject. I realise that this is not always possible, since with my subjects of choice I often find that I am limited even when using a 600mm lens. in normal situations though when you are not FL limited you are just going to resample either down some for a small print, or up a bit for a larger one. Back when I shot film and had my own darkroom I usually printed at 5×7 and 10×8, but now with digital I don't normally print anything smaller than 16×12, resampling the image to 4800×3600 Px.

Remember usually cropping and resampling are two different processes, used for different purposes.

Alan

I agree. What it seems like to me is that some of the images in the lens sample forum are cropped so tightly to fill the frame with the subject that the image has to be resampled to enlarge it to such an extent that pixelation starts to become noticeable. Then when I look at the images I begin to wonder about the IQ from that lens. I notice this mostly with the super telephotos and zoom telephotos. Some of the shots I'm looking at and saying to myself: "Nope never trying that lens". But I think the issue is not so much the IQ as the processing and resampling of the image.

I will crop a photo to well match the ASPECT RATIO of the print to be made, and ensure that the file I send is at least 300 pixels per inch of print.

So if a photo starts 3000 x 4500 for example, and
if I want a 5" x 7", I send a 3000 x 4200 pixel file
if I want an 11 x 14", I resize by 1.1x and then send 3300 x 4200 file

I do pretty close to what Wilt does as well. I crop for composition and aspect ratio. If the resulting output has to be a certain size, I resample accordingly if needed for the dimensions needed for that output at 300dpi.

In lens sample threads people will often crop the image so that it is at 1280 px or less on the long edge, to match the maximum size for display on POTN, or for older posts 1024 Px which used to be the max size on this site. This would be what is known as a "100% crop" and ensures that the image is reproduced on screen pixel for pixel without any interpolation*. These crops are used so that you can accurately judge the quality of the image without any of the software being used affecting image quality. Anything that requires the computer to resize the image for display on the screen will usually favour speed over quality, and so be a bad thing.

* Windows 10 has now got a built in screen resizing system that effectively allows you to run the computer screen at a different scaling to the native screen resolution (and I hope that OSX has one as well now). This has been introduced mainly for those that are using very high resolution monitors. Your average computer monitor generally runs at a linear resolution of between about 96 and 110 PPI, Windows for example has assumed a screen resolution of 96 PPI since at least the introduction of Win 95. The thing is though that modern QHD and higher screens are at much higher resolutions than this. I'm using a Dell UP2715K monitor that has a resolution of 5120×2880 pixels giving a linear resolution of 219 PPI. While a 27" 4K display will be IIRC something like 180 PPI. Windows by default sets my screen to run at 200% so that all the screen features look to be the same size as on a screen that was running at 109.5 PPI.

I actually run my monitor at 175% as I find this scaling is still easy to read, and I get a little more screen real estate. I have a friend who uses a 3-4 year old iMac and he has to change the actual screen resolution down from 2560×1440 to the next lowest setting because of poor eyesight, as we can't find a screen zoom control on his version of OSX. He has to do the same on older Windows computers too. This method of changing the screen resolution on an LCD display is not very good at all, so he would do much better with the screen zoom control in Win 10. As with a normal resolution screen he could set the zoom to a higher value, and Windows would handle the interpolation of screen features in a much better way.

Most web browsers now also seem to have a general page zoom function, well Chrome, my browser of choice, Edge and IE all seem to have this. This also allows you to generally change the on screen size of various page elements. So it is perfectly possible that you could be running both the OS and the web browser at other that 100% view, which of course would mean that you might not actually be viewing an image on screen at the expected 1:1 image:screen pixel relationship. So it can be worth checking this stuff out in your computer settings, to ensure that you are seeing what you expect to see.

Also be aware that most actual image viewing and editing programs will be aware of the screen magnification settings, so that when you view an image at 100% you are getting a true 1:1 representation on screen.

Alan

Oh and sorry the addendum ended up being longer than the actual post, but I thought it was useful information to know about.

I do not crop on export, I print from LR.

kf095 wrote in post #18429202
I do not crop on export, I print from LR.

apparently the TF thought otherwise!