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Increasing JPEG filesize without losing quality

Anton Bredell , Jul 23, 2006; 12:51 p.m.

I am currently using Rawshooter essentials to convert RAW files to JPEG.The resulting JPEG's are 3.1MB in size.After converting them to JPEG, I use Photoshop7 to retouch if needed.I am submitting to a site that require 6MB and larger JPEG's.How do I go about increasing the JPEG filesize without losing quality? Is this the best workflow to use? Do I lose image quality each time I work on and resave a foto? Will appreciate any feedback. Thank you

Responses


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Pico diGoliardi , Jul 23, 2006; 01:20 p.m.

You cannot increase a raster image's size without loosing something, unless perhaps it's a subject with no luminance changes, flat colors, all within the scope of a GIF file (for the web). It is a matter of physics, of fact.

The best you can do is to interpolate in 10% increments with very modest unsharp mask applied at certain stages. In your case the increase is not severe so try that. I forget if PS7 has actions, but if it does, use them and be happy.

Just don't waste any money on Fractal Magic and similar theftware.

Joseph Allen , Jul 23, 2006; 01:41 p.m.

Anton, if you need to save, do edits and resave, etc. then jpeg will lose some quality each time. You are better off converting to a TIFF file, doing all of your editing and saving/resaving in that format and then converting to jpeg as the last step if you want to send smaller files to your lab or whatever. Incidently, if you feel the need to resize them to bigger files to send to your lab for printing, I personally wouldn't bother. I would just sharpen appropriately and trust the lab's printer to do the interpolation for you. In my experience they have always done as good or usually BETTER job than I could do myself of resizing.

Bill Tuthill , Jul 23, 2006; 02:02 p.m.

If you discared the original RAW files, as you seem to be implying, you'll find that the Lanczos filter (free in ImageMagick or IrfanView) does a better job of upsampling than Photoshop, even the 10% at a time trick Pico recommends. Hopefully you saved high quality JPEG with 1x1 chroma subsampling, because those up-res fairly well.

In the future, save your frickin' RAW files!

David Arran , Jul 23, 2006; 07:32 p.m.

Is the 6 Mb requirement compressed or uncompressed? If you look at a jpeg file size on disk, then you're looking at the compressed size. However, if you open the file in (say) Photoshop, then the software decompresses the file and reports the uncompressed size, which will be a lot larger. Check with the site that you're submitting to.

James Hart , Jul 23, 2006; 08:24 p.m.

If you HAVE to submit the files as JPEGs, then lower the compression rate. I usually use Paint Shop Pro, which allows me to change the compression rate when converting a file into a JPEG. I assume Photoshop does as well since it has more features than PSP. You could also increase the # dots per inch/cm. It would be best to do either of these things the 1st time you are saving the file as a JPEG, since as another person above noted, you do lose data every time you re-save a file as a JPEG.

Steve Dunn , Jul 23, 2006; 08:33 p.m.

JPEG is not a good file format to use for an intermediate file; if you have to save a file from your RAW converter before opening it in your editor, save it in a file which does not use lossy compression, and if at all possible, it would be wisest to save it at 16 bits. If you save your intermediate files using lossy compression (which is what JPEG uses), then yes, you lose image quality each time you go through an open-work-save cycle.

I don't shoot for any sites which are dumb enough to set such a minimum file size so I haven't had to upsize files to meet such an arbitrary requirement. But others have given you some suggestions on how best to resize so hopefully you'll be OK there.

Peter Blaise Monahon , Jul 23, 2006; 08:34 p.m.

.

I think that you might be misunderstanding their requirement.

A 6mb JPG means nothing since JPG file sizes depend on too many variables to be predictable, like mage content (complex or simple, sharp or unsharp), image size (pixel dimensions), and compression ratio - all could ve vastly different to make a srotage file size of 6mb.

I think they mean 6mp capture, meaning

~3,072x2,048 pixels = 6,291,456 pixels = 6mp for film scans at a 1.5:1 aspect ratio, or

~2,929x2,148 pixels = 6,291,456 pixels = 6mp for typical non-35mm digital capture of 4:3 aspect ratio, or

for square film = 6mp^2 = ~2,509x2,509 pixels = 6,295,081 pixels = 6mp.

Maybe they mean 6mb after expansion on screen, and in Adobe Photoshop, it tells your the "expanded" file size regardless of the original JPG compression, and it's 3x the pixels dimension since it really has 3 pictures inside - one red, one green and one blue!

35mm scan at 1.5:1 aspect ratio then = 1744x1183 pixels = 6mb

digital 4:3 aspect ratio = 1673x1255 = 6mb

square = 1449x1449 = 6mb

It all depends on thier meaning of 6mb expanded file size on screen in 8-bit color, or 6mp camera is required as a minimum capture? Tell us more.

And JPG is a final output format never to be re-edited again (a crime and a sin to edit a JPG and resave as a JPG), especially by you. You should work in TIF and only convert to JPG once before sending the file out at 100% (or 0% compression) for stock, and anything lower for display only, like 65% to 85% for web display, but of course, web display also expects resizing down to only 1,024x wide or less, of course making smaller storage files.

Let us know some specifics of the place your're sending them to so we can read the requirements and help you interpret them better.

Or ask them to explain and tell us waht they say - don't make us speculate when you don;t know enough to quote and understand their entire requirements!

Click!

Love and hugs,

Peter Blaise peterblaise@yahoo.com Digital Photographer http://www.peterblaisephotography.com/

Tony Torres , Jul 24, 2006; 04:38 a.m.

well there is a great program called Geniune Fractels thats a program that would definitely work for you Tony

Peter Blaise Monahon , Jul 24, 2006; 07:19 a.m.

.

Ahh ... we need to wait for Anton to get back to us with answers to our questions - what are the specifics (links?) of the requirement, as "6MB JPG" seems to be a misunderstanding.


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