Hi guys, I have a few technical questions which I am very confused.

I always have been using 240dpi when saving my raw files in ACR with my FF camera. I just noticed that there's a dpi setting in the OMD as well and the default number is at 350dpi.

What number do yo use here? Would it degrade the quality of the jpeg/raw output if I set it to 240dpi?

Second question is, I am used to FF or APS-C aspect ratio (Image Aspect) of 3:2 or roughly 5616x3744 in FF. The default setting in the OMD is 4:3 or roughly 4608x3456. If I choose the 3:2 ratio I get 4608x3072.

My question is, does it degrade quality if I choose 3:2 over 4:3? Or is it just the cropping?

Thanks!

I would suspect that changing the aspect ratio would make the output area SMALLER, because you can't go beyond the size of the sensor as it is. You'd have to cut area out to get to the new aspect ratio. That shouldn't change the quality of the image, only the size.

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- DPI is a fairly irrelevant, outdated measure. Simply a flag in the EXIF that tells certain devices how big a print should be. Doesn't affect the image itself at all, resolution (pixels) is all that really matters.

- The RAW file will always capture the full 4:3 image. The other aspect ratios are crop settings and apply to JPG files, so you simply cut off part of the picture, nothing else.

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It has no effect on JPG either. It functions as a scaling factor. If your editing software defaults to 350 dpi, then a file would show as being be 4608/350 inches wide. Set it 240 and would show 4608/240 inches wide.

Not exactly, it's just as relevant today as ever. It tells the software how many pixels from the image to print within one inch of paper. If you have a 300x300 pixel image and you set the dpi to 300 you'll get a one inch square. If you set te dpi to 150 you'll get a two inch square. 600dpi a 1/2 inch square.

The thing about DPI is you can set it any time before printing, and you can change it as many times as you want since it's just a stored number.

If you always print at the same DPI it makes sense to set the default in the camera...but if you crop, and or print to a different size paper it would make more sense to set the print dimensions and et the software figure out the di for itself!

++1

The PPI setting in an image file is a very useful feature.

I didn't see an answer to the question "What number do yo use here?" I didn't realize that it was adjustable. I am used to 300 dpi, so I would change it to that. Now I need to go find out how to adjust it!

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My point is that unless you print yourself, it's pretty pointless. I don't print to a specific DPI level, I print to a certain size. I check DPI to get an impression of whether my resolution is good enough, no more, no less, and what DPI I accept depends on viewing distance.

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I will try to explain briefly the use or "DPI", please excuse my English.

Prints and printers use different numbers of "dots per inch", depending on the quality of paper and the quality of printed material. A very high quality image book could be printed with a very high "DPI" number, a current magazine with coated paper perhaps will use 300 DPI, a newspaper something around 72 DPI. It has to do with how much ink will be put on the paper, depending of the "grid" of the printer device. If you print with 300 DPI on newspaper paper, you will get a mess, if you use 72 DPI on a very fine and coated paper, the image quality will be coarse.

On the other hand, you have an image size and type that can be "adjusted" to the amount of DPI needed for printing purposes. Normally an off-set will print with at least four different inks: CYMK or cyan, yellow, magenta and black, an ink-jet printer will use just three channels: RGB, red, green and blue.

You can downscale your image to fit exactly to the size needed, but you can´t upscale it. If you do, your software will be interpolating - in other words, inventing - dots to get the amount needed. This means that, if you want a real high quality image printed on a very fine paper, you will need to start with an image that has at least all the needed information for the final size. This is one of the reasons because FF cameras are needed to produce such large images: they will allow to print large high quality images on high quality papers. If you don´t intend to use your images for this purpose, the size can be a lot smaller.

Note that if you submit images to scientific publications they insist on 300dpi as a minimum. Generally the paper quality in the printed form cannot support more than ~100dpi so it is largely atavistic holdover from who knows where.

Upsizing an image to get the print size desired so as to conform to the 300 dpi minimum is fine so long as the perceived quality of the printed image is still OK.

Try explaining this to researchers is almost pointless so I just resize the image and say "here you go" ... kind of expect more from them but really not worth the effort.

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