Today’s Question: At times I need to upload a photo for online judging, and the site requirements are for a JPEG file of at least 1200 pixels on the long side and a maximum file size of 5MB. What’s the best way to save a JPEG and greatly reduce the file size down to 5 MB without lessening the photo quality?
Tim’s Quick Answer: I recommend saving the JPEG images with pixel dimensions of 2,000 pixels on the long side and with the Quality set to about 80%, which virtually guarantees you that the files will be smaller than 5MB.
More Detail: There will always be some degree of image quality degradation when reducing the pixel dimensions of an image and saving as a JPEG file that always involves lossy compression. However, with adequate pixel dimensions and a relatively high setting for Quality, the results will be perfectly adequate for evaluating the images. For example, a sharp image won’t appear to be out of focus when saved with these settings.
JPEG images will generally be smaller than 5MB in size until you get closer to around 3,000 pixels on the long side with the Quality setting at about 100%. The file size will vary for each image based on the content of the images, but even with these settings most images will be smaller than 5MB. There’s no need to adjust the pixel per inch (ppi) resolution, as that doesn’t impact the file size as long as you’re resizing based on pixel dimensions.
In most cases images are likely to be reviewed with a monitor display resolution of around 2,000 pixels across, though this can obviously vary wildly depending on who will review the images and what type of display and settings they’re using. But in terms of evaluating images for a photo contest, an image that is 2,000 pixels on the long edge is totally adequate in my view. If you’re concerned about the level of detail, especially if you feel the judges will zoom in, you can increase the size somewhat, but this will risk causing some files to exceed the 5MB limit.
A Quality setting of around 80% (a value of around 8 to 10 if you’re using Photoshop to save the images) will result in very good quality. Quite frankly, if a judge reviewing a JPEG image deducts points due to the detail not being as great as the full-resolution image or due to visible JPEG artifacts, they really shouldn’t be judging this type of contest.
Also keep in mind that you’ll have a relatively level playing field if all images are being submitted with the same basic limitations. But pixel dimensions of 2,000 pixels on the long side with a Quality setting of about 80% will pretty well ensure that all images are smaller than 5MB while still providing perfectly adequate quality for evaluating the images.
