Not being a serious photographer I keep all the photos downloaded from my camera as *.jpg files. Material that I scan I used to keep as *.bmp files (being a non-lossy format). Recently however I have started to keep scanned material as *.png files which appear to have the advantage of being non-lossy with a reasonable amount of compression.
Apart from apparently not being compatible with Yahoo e-mails do other members have any views on this subject ?
Thank-you "Administrator" for creating a new board for my query - I think the whole question of Board-Headings on this Forum probably needs reviewing in the light of a few months usage and before it becomes impossible to change.
Post by numbercruncher on Sept 7, 2018 13:14:23 GMT
For the BMP's consider zipping them which brings about the same compression as PNG. Your comments on PNG are correct, however, I'm unsure why scans need to be 'lossless' (24-bit colour depth still means colour approximation, although the human eye can't make the distinction), and a high quality jpg still takes a lot less space than a PNG. Actually I would probably save my photographs as 'raw' and my scans as JPG.
For good measures I've run a test just now, a JPG (of an Antonov-2 parked at Xertigny-Moyenpal) made by a Canon EOS, 4608 x 3456 pixels, transformed to BMP, then to PNG, and zipped the BMP twice. Differences are: JPG: 5.169 KB ZIPX: 22.245 KB PNG: 26.098 KB ZIP: 31.802 KB BMP: 46.657 KB
Interesting to note is that the proprietary 'superzip' of WinZip (licensed software) achieves better compression then PNG.
So, yes, PNG achieves better image-per-gigabyte ratio then 'bare' BMP, but I'm unsure about the reason for lossless scans. But that was out of scope anyway.
The important thing with jpg's is the compression factor Save and open a file at 70% each time and after 3 shots you are at 70%x70%x70% which, in my head, is approx 35% of the original quality. I only ever save jpgs at 100% now but often start from RAW anyway and using Lightroom, you leave your original untouched and export your changed file to a jpg, dng, TIFF or whatever Using 100% I see no degradation whatever from the original Just looking at the Fokker (He typed carefully) in this album www.flickr.com/photos/elaref/sets/72157631706129587/ 2 images were opened, saved and closed 50 times. Compare full screen with the original
Thank-you for your responses which have given me food for thought. A few words of explanation might not come amiss.
As I said, I am not a serious photographer and I am certain that my simple camera will output nothing but jpegs. Most get deleted immediately they hit my computer and the better ones simply get stored with little manipulation (perhaps straighten and crop).
Scans on the other hand are mostly taken from old black and white prints which are usually dog-eared, scratched, and creased, whilst the standard of original processing often leads a lot to be desired. I sometimes spend days using Photoshop to remove these types of imperfections from a copy of the original scan and often go through many iterations until I achieve a satisfactory result, although I draw the line at any manipulation that alters the basic subject of the photograph.
I hope this explains the background to my original question.