File Size, Print Size, DPI, PPI, blah blah blah...

Okay, so...explain to me a little bit about file size and print size. Here's your example...


A friend gives me the original file to edit, I edit it. I send him the edit and he says "Hey, the original was a bigger file size than the edit, what's going on?". I give my usual "file size is meaningless towards actual physical print size, blah blah blah..." speech that I give people when they ask about printing and sizes and whatnot. Whether I'm right or wrong, I'd like to know what the actual truth of the matter is.

What does File Size have to do with resolution, printing, pixel dimensions, etc.?? If both images are 240PPI, 15"x9", 3720x2171, why does file size change and does it matter?? What magical piece of the puzzle am I missing?

HTTP response: 404 | MIME changed to 'image/gif' | Byte size: ZERO | PHOTOBUCKET ERROR IMAGE

HTTP response: 404 | MIME changed to 'image/gif' | Byte size: ZERO | PHOTOBUCKET ERROR IMAGE

If you saved your file using a lower quality setting, the amount of compression will increase, resulting in a smaller file without changing the pixel dimensions of the image.

Edit: the changes you made to the image may also have caused the compression ratio to increase (e.g. going from color to b&w), resulting in a smaller file.

You will be better helped in the RAW and PP section.....check this FAQ out - helped me.

https://photography-on-the.net/forum/showthre​ad.php?t=138533

My guess would be compression of the file is different in both cases. If you want to see this in action, make a totally white or totally black jpeg, with specs of 240PPI, 15"x9", 3720x2171 and then see how small the file is. It should be substantially smaller than your pics above.

File sizes vary depending on, well, various things. You won't get the exact same results. You have the right image size settings, an make sure you save as a High quality.

Hmmm, maybe my question was not quite the question I thought it was. How's this...


Does file size make a difference??

And if it does, why does it make a difference?

One thing that will have some effect is the fact that when you open a jpeg, do something, then save the jpeg, your jpeg process will re-compress the jpeg image. This is "bult-in" to jpeg processing. So to minimize the re-compression "damage" you want to have the jpeg Quality set to high.

Anyway, this process will have some affect on the file size, but as to how much...well, it depends...?

So, the one thing to ensure is that you are retaining image quality. The actual file size means nothing in and of itself -- different things can affect it. Different software apps can use somewhat different processes in saving. The one thing to be concerned about is the Quality.

katodog wrote in post #13230971
Hmmm, maybe my question was not quite the question I thought it was. How's this...

Does file size make a difference??

Most of varying file size of a jpeg file is due to different quality settings when you save the file. So yes the file size makes a difference.

katodog wrote in post #13230972
And if it does, why does it make a difference?

Because the smaller the file size, the more you've compressed the image. Now whether that compression (with jpeg, "compression" also includes "loss of detail") is visible in the final product or not, you might question. But certainly if you compress from level 12 (typical in-camera least compression) to level 10 or 8 (typical print or web compression) the file will get a lot smaller due to compression.

Dave

tracknut wrote in post #13234526
So yes the file size makes a difference.

Does it matter to print size?

katodog wrote in post #13234606
Does it matter to print size?

You mean the physical dimensions of the print? Yes, it all matters, but practically the answer is always going to include the caveat: "but it depends whether you can see the artifacts from the compression". So personally I save my print files at level 10, and digital files at level 8. Why? Because when I print for some reason I can more clearly see the banding artifacts (for example in a blue sky) than I can see them in a digital file. So while I know I'm losing detail in both those files (from the original), I figure if I can't see it, my customers can't see it, and why save a larger file if it's not needed.

Dave