[Leica] Large JPEGS, TIFFs, C-41

[hlritter at bex.net (Howard Ritter)]

+1

I know the purist lore is to shun JPEG like someone just back from the Ebola 
zone but when I have my camera save an image as both a JPEG file at 
relatively low compression and a RAW file and then view them side by 
side?whether small, medium, large, or pixellated large?I have rarely been 
able to detect any difference. (I guess that?s due to the fact that the ?PE? 
in JPEG stands for ?photographic experts?.) That?s why I basically stopped 
saving RAW files and now have the camera record just highest-quality JPEG 
images. If you have your film processed by a facility that scans only to 
JPEG, talk to them and make sure they use the lowest compression (i.e., 
largest file size/highest quality) setting available on their equipment. 
That?s the first key.

The second key, as Sonny says, is not to save a manipulated JPEG image as a 
JPEG. Open, view, and close, OK. Open, massage, and save as JPEG, not OK, 
because serial compressions will degrade image quality. Open, massage, and 
save as TIFF, OK. The only problem might arise from the fact that that a 
TIFF file is 3x the size of even an original RAW file: RAW saves the 
single-color information from each R, G, or B sensor photosite, and display 
software interpolates a full suite of RGB information for each pixel when 
the image is opened. When it?s saved as JPEG, only the individual R, G, or B 
value is saved for each pixel. But when it?s saved in TIFF, the interpolated 
suite of all 3 color values is saved for each pixel. So the 10 MB 
max-quality JPEG image I just now looked at from my 24 MB sensor (that would 
have yielded a ~24 MB RAW file) became a 72 MB file when I opened it and 
saved it in TIFF. This bloat can be somewhat ameliorated by electing 
lossless compression of the TIFF file if your image-processing app offers 
it. When I saved the TIFF file with LZW lossless compression it shrank by 
~50% to 37 MB. The ZIP file of the same TIFF was even smaller, 33 MB, and is 
also lossless. Serial open?massage?saves with lossless compression won?t 
introduce artifacts because here the decompressed file is an exact duplicate 
of the original.

I don?t know if there?s a lossless file format that saves only single-color 
information for each pixel, mimicking an original RAW file.

You probably know all that already, so take this as one user's experience 
that virtually nothing visible is lost with a primary low-compression JPEG 
file.

?howard


> On Apr 29, 2015, at 7:19 AM, Sonny Carter <sonc.hegr at gmail.com> wrote:
> 
> Peter, the loss with pegs comes when you re save as JPEG over and over.  
> If you keep the JPEG, or a direct copy of the file as a master, you'll 
> incur very little loss. 
> 
> For good documentation on scanning, see www.scantips.com  page 9 is about 
> file types. 
> 
> from my iPad
> 
> Sonny Carter