APP
Topic Author
Posts: 502
Joined: Mon Feb 21, 2000 7:11 am

TIF Vs Jpeg / Compression

Thu Oct 19, 2000 8:15 am

2 QUESTIONS.........
I've noticed many of you use the TIF format to work on your pictures before converting to JPEG for submission, what's the advantage in doing this?
also, I realise that this is probably a dumb question but how do you alter the compression for submitting pictures. (I'm using Adobe PhotoDeluxe Business Edition 1.1)
I've currently got 82 photos on the site and am finding it increasingly difficult to get more of my shots accepted, and am therefore exploring ways of improving the quality af my scanning/manipulation to get back on track.
Thanks in anticipation.
APP
 
Brick
Posts: 1488
Joined: Wed Aug 04, 1999 11:08 am

RE: TIF Vs Jpeg / Compression

Thu Oct 19, 2000 9:39 am

Basically, anytime a file is compressed there is a loss in data. TIFF files have no compression (1:1) which is why they are so large. JPEG files are compressed which results in some data loss. Depending on how you want the quality and file size, generally JPEG is 1:4.

When the digital processing is done on images (color correction, gamma adjustments, etc...) you want all of the pixels present while doing this....thus you use TIFF format. When everything's done the way you like it, the final step is to save it in a compressed format like JPEG.

Mark Abbott
Minneapolis, MN
A noble spirit embiggens the smallest man...
 
hawaiian717
Posts: 3139
Joined: Tue May 18, 1999 2:46 am

RE: TIF Vs Jpeg / Compression

Thu Oct 19, 2000 9:45 am

The problem with JPEG is that its compression algorith is lossy, meaning it drops some data each time it is used. In plain English, your file gets worse every time you save it. Thus, you want to make saving in JPEG format the last thing you do before uploading.

But often times you will want an original copy that you can later work on without having to rescan, or perhaps you are scanning in one program and editing in another, or making edits in more than one program. Thus you will need to save your image in a format that does not lose data each time like JPEG does. TIFF is one such format that is popular; personally I use PICT which is a more common format on the Macintosh. But both TIFF and PICT are much too big to be used on the Internet. For example, one of my photos that I have in both PICT and JPEG format on my hard drive is 1.4MB as a PICT, and 92kB as a JPEG.

Regarding your second question, I don't know Adobe Photo Deluxe specifically, but in most of the image editors I have used, there is some sort of "Options" button in the "Save As" dialog box, if you click it while JPEG is selected as your format, there should be some sort of option. It could refer to either "Compression" or "Quality". For Airliners.net, you want maximum Quality or minimum Compression. This is because Airliners.net has its own routines to optimally compress the image, so you want to give them the best image you can to start with. These files are generally pretty big, so if you are uploading them to your own site, you will want to save another copy (from your TIFF original, not the JPEG you just saved; see what I just wrote above) with a slightly lower Quality setting or slightly higher Compression setting. In one program that I have used a lot, GraphicConverter, the setting refers to Quality. Airliners.net images saved at 100% Quality are often over 400kB, while versions of the same imaged saved for my own web site are done around 75% Quality and file sizes tend to hover near 100kB, with very few visible differences.
 
bodobodo
Posts: 545
Joined: Wed May 03, 2000 6:43 pm

RE: TIF Vs Jpeg / Compression

Thu Oct 19, 2000 12:12 pm

One thing that should probably be clarified to avoid some confusion. You can also have compressed TIF files (lzh-type compression if I remember correctly) but this is lossless compression much like the sort of compression in Zip files where nothing is lost but somehow the file size can be reduced. The amount of compression possible for a given Tif file depends on the nature of the data in the image. There is no danger of lowering the image quality when doing so. The only disadvantages of working with compressed Tifs are that some programs can't handle compressed Tifs and the decompression/compression required when opening or saving a compressed Tif file takes a bit longer. It's probably a good idea to keep them uncompressed while you are actively working with them and then perhaps compressing them (within the image editing program by choosing Save As and choosing an option for compressed Tif or by just incorporating many of them into a zip file) when archiving them on your hard disk or CD-R for later use. The situation is different with .jpg because the lossy compression method there actually discards information as the file size is compressed further. This is why most image editing programs indicate jpg compression on a sliding scale based on % compression, image quality, or file size. For Tif compression it is either compressed or not.

Cheers,
bodobodo
 
PUnmuth@VIE
Posts: 3119
Joined: Thu Aug 24, 2000 9:31 pm

RE: TIF Vs Jpeg / Compression

Thu Oct 19, 2000 4:05 pm

I'm using irfanview to reduce my files in tems of size. That's a really good freeware to manipulate your pictures. I think here are no webpages allowed ao mail me for the URL if you would like to know it. I'm reducing the size of my camera files (I'm shooting digital in jpg mode because TIF takes a lot too long to save the file in the camera) from 2048 on the longer side to 1024 and set thte jpg compression to minimum (equals highest quality) to submit the photos to airliners.net
Peter
-
 
USAir_757
Posts: 949
Joined: Wed Jun 14, 2000 12:30 am

RE: TIF Vs Jpeg / Compression

Thu Oct 19, 2000 4:36 pm

In PhotoDeluxe, you go to Export, then go to Other Export, save as a JPG and click OK. After you do that, it will display a box. Click Options on that box, and under quality select Maximum.
-Cullen Wassell @ MLI | Pentax K5 + DA18-55WR + Sigma 70-300 DL Macro Super
 
APP
Topic Author
Posts: 502
Joined: Mon Feb 21, 2000 7:11 am

RE: TIF Vs Jpeg / Compression

Fri Oct 20, 2000 7:09 am

Thanks for all your input, you've all cleared it up for me pretty well. I'll rework some of the photos that have been rejected and see how it goes. (Fingers crossed!)
Watch this space!!
Cheers,
APP
 
User avatar
Bruce
Posts: 4935
Joined: Tue May 18, 1999 2:46 am

RE: TIF Vs Jpeg / Compression

Sat Oct 21, 2000 2:43 am

Maybe that is one of my problems too? When I scan it saves them as TIF right off the scanner, so maybe I should do the editing before coverting to JPG ??
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
bodobodo
Posts: 545
Joined: Wed May 03, 2000 6:43 pm

RE: TIF Vs Jpeg / Compression

Sat Oct 21, 2000 2:47 am

Bruce,

Definately keep them as .tifs throughout the editing process. Make saving them as .jpgs (with minimal to no compression) the last thing that you do before submitting while keeping a copy of the original .tif as an archive.

Cheers,
bodobodo

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