Hi folks. Wonder if I can get some help. I don’t enter photo contests very often but I did enter one which apparently has made the final step. They have asked for a high resolution JPEG file with a maximum of 20mb.
What settings do I use to yield the highest quality JPEG? Under the resize option in PL4, what resolution do I indicate? Do I also check enable resizing and enter 20mb for sizing? What interpolation do I use? Any help is appreciated. Thanks in advance.
The problem you have is the mixture of terms that the contest organisers and yourself are using.
On the one hand they are asking for a high resolution file with a maximum file size of 20MB.
On the other, PhotoLab doesn’t have an export option explicitly for file size; the nearest you can get is Megapixels, but that can give you all sorts of file sizes depending on what quality you specify for the jpeg compression.
Let me take one of my files from a Nikon D810, 36 Megapixels where the RAW file is 79MB.
I export it at full size and 100% jpeg quality and get a jpeg file of 75MB. The resolution is marked as 72ppi but that is totally irrelevant because changing that will only change the physical printing size, not the size or quality on screen.
Next I export it at 80% jpeg quality and, this time, I get a jpeg file of just under 15MB; exporting at 90% gives me just over 22MB.
You asked what settings you would use to to create the highest quality jpeg, but then you ask what resolution to use. As I said, resolution is irrelevant unless you are wanting to print the image to a certain size - exporting at 300 ppi yields exactly the same file size as exporting at 72 ppi.
You don’t need to worry about interpolation unless you are reducing the pixel size of the image.
If I were you, unless your image is already smaller, I would enter a “longest edge” figure that gives you a 24Mpx image size (at 3:2 proportions, that would be 6000px). The resolution can be anything you want (most modern larger screens are around 110ppi; for printing you would set it to 240ppi). Then I would use bicubic interpolation if your original file is significantly larger or bilinear if it is already at or near 24Mpx. Finally, I would start at 100% jpeg quality and just keep on reducing that until the file size is smaller than 20MB.
I can’t think of any other way without losing control of the quality of the output, which you want to be the best possible within the given file size.
The RAW file is 85MB.
They want a print quality for the magazine in case it is a winner.
This stuff is really confusing to a newbie!
Any advice?
Thanks Joanna. Very much appreciate your help.
So I tried what you suggested. I get a 17.9MB JPEG with dimensions 4003x6000 and 400x400 resolution. Would this be a high quality image they can use for printing?
How would I increase the file size to 20MB as they asked?
This is really confusing for a newbie. Is there a tutorial on exporting files? I don’t understand the longest edge part of your response. What did you suggest 24mpx and how did you arrive at 6000px?
Thanks again for your help.
Like I said before, you can use whatever number you want for the resolution. For printing you would expect to use 240ppi (no higher) for a print that would look good at arm’s length.
Either increase the dimensions or the jpeg quality.
It’s pretty confusing for most people but competition organisers seem to delight in throwing up something to trip people up.
24Mpx is the average APS-C sensor size and, if the format is 2:3, 2 equates to 4,000 and 3 equates to 6,000 - 4,000 x 6000 makes 24,000,000.
What size in Mpx is your original file? Or what are the original dimensions?
Thanks Joanna. The original RAW file says 85.7MB and 7952x5304 in the EXIF data.
Really appreciate your help. I will eventually figure this out. I was using a SONY A7r3 which is a full frame 42mp camera I believe.
Dale
I think you are just going to have to try different combinations and see what gives you the best result.
Sorry but fitting that much information into 20MB is always going to be a compromise.
Wonderful! Thanks so much for your help Greg. I am forever grateful!
If I had a dollar for every time I was asked to help create the likes of a “high resolution JPEG” or such for online use… 
Fortunately there are still great people out there who are willing to help others who are learning. I am sure at one time during your photography journey someone has given their time to help you. Or perhaps not - maybe you were a know it all from the beginning.
It’s easy to sit behind the safety of your keyboard and be rude. It’s much harder to help others.
for printing you would set it to 240ppi
Huh? As far as I know Canon and HP printers have a native resolution of 300dpi. I know for a fact that my, and other, Epson printer’s default is 360 dpi. Given that why would you use 240?
stuck
Sorry, that didn’t come across as I intended. My eye rolling is reserved for people who set requirements in obscure or impossible ways.
Because pixels in an image are not dots of ink. Printer resolution is measured in dpi, image resolution is measured in ppi.
With larger prints, you need more than one ink dot to represent one pixel and most of those printers are usually used at multiples of their “native” resolution
2287x1525=3487675 pixels. Since we’re talking about jpeg, every pixels takes 3 byte so that image will be 10463025 byte or 10Mb. Irrelevant of the desired ppi.
George
Sorry. You’re trying to find an image size in pixels that will give a file size of 20mb. I didn’t see that.
George
pixels in an image are not dots of ink
Ah yes, I made the schoolboy error of mixing terminology, dpi and ppi. That in turn made me do some Googling, which turned up this post on the Cambridge in Colour forum:
https://www.cambridgeincolour.com/forums/thread58433.htm#post670050
I think I’ve got my brain around it now.
stuck