batch process - uniform file size - how?

A client wants 3Mb JPegs maximum (to save server space)- there will

be hundreds of these - I'd like to hit that 3Mb on the button for

quality reasons but cannot find a way to batch process for a final

file size preserving picture proportions - in either PS or Pro Photo

Zoom - anyone know how to do this ? apart from 3am sessions which

I'd rather avoid as there's a few hundred more to shoot each day for

the week. Thanks for thinking.

I don't need uniform width and height - just uniform file size - indeed there will be a fair amount of cropping and adjusting with variable frame sizes as a result - what I then need as a final step is a resize to make them all hit 3Mb - which seems like something PS could manage if I talked to it nicely.

Derek, JPEG compresses based on the content of the picture e.g. sky (less detail) is more compressed than trees (more detail). This is why you won't find an easy way to control to exact file size. You would have to iterate and check, change compression ratio and do again. Even then you wouldn't be able to get "exactly" 3mb. You would be better off, for quality purposes, to aim for an average file size of 3mb. The best you could do the other way would be an average less than 3mb.

You'd probably have to write a script to try a setting, then try another setting that gets you closer etc. until you've come up to a file size close enough to 3 MB (or was it megabits you meant? a significant difference.) Needless to say, this isn't very practical, so what I'd do is guesstimate a good compression factor that typically keeps you below your limit and batch process with using it. Adjusting quality for a gain for a few percent is just a waste of time.

Use "Save for Web" and click on the Right Arrow on the preset pane to reveal a drop-down menu. Select "Optimize to File Size".

Oscar - tell me more about Mbytes v megabits - the spec document actually says "3 Megabit" - which I took to mean 3 Mb and looking the word up doesn't show a difference I find significant - thanks to all others with differing approaches - my problem is I'll be filing 300 pictures per day for five days and that doesn't leave time for individual attention - at present I have actions that will do all of what I think I need except hitting that final size parameter - my simple mind reckons that if PS can recalculate the file size from resample data then it ought to be possible to do that the other way around and tell the prog the final size desired and picture proportions. thanks all keep 'em coming.

There is no easy way to do what you want to do automatically,

and perhaps your goal is unrealistic. Some programs try to do this, but they recompress the Jpeg's which is a bad idea. Save for Web>Optimise is your best option.

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Some digicams include this option, but they must use the same iterative procedure mentioned by Oskar, since this is not a standatd Jpeg feature.

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Jpeg2000 does include this option, but that won't help you with ordinary Jpegs.

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Read more in my article on <a href="http://www.photo.net/learn/jpeg/">Jpeg Compression</a> (http://www.photo.net/learn/jpeg/)

"I'd like to hit that 3Mb on the button"

 

The client's request for a certain file size is due to his server limits. He has not asked that each file be exactly 3mb. You are imposing this yourself, or atleast that's the way it reads to me.

 

Why jeapordize image quality by adding your "personal" requirement that each file be spot-on that size. I would pick a x and y dimension and a compression that give approx. 3mb, and leave it at that. I would think he would be less than impressed by varying file dimensions and compression.

The contract specifies files no larger than 3 megabit (sic I hope) Their maximum print selling size is 12"x8" so it had better be Megabytes. I find that file size small and want to be as close to the limit as possible. Whilst processing an estimated 300 pics per day I also have to be taking 300 pics per day all week - hence the need for as much auto processing as possible.

Any Jpeg larger than 2MB should be adequate for an 8X12 print!

Make sure that you have the pixels to print at 300 DPI (i.e. 2400X3600 pixels).

 

What you should try is a batch conversion at a fixed quality setting, and then redo those files that are too large or too small. It is time consuming, but there is no easier way.

Re <I>1 byte is 8 bits</i><BR> 4 bits is one 1 nibble; or 1/2 a byte. There are 2 nibbles per byte. Thus a 3 Megabyte image is a 6 Meganibble image. :)

Thanks Gordon (and everybody - but Gordon hit the thumbnail on the head at my sort of level). So now I have a 300dpi 3600x2400 pixel action and saving at High Quality "11" gets under the wire - so if I have a landscape and a portrait action I should only need to sort them into those categories ( or rotate the portraits until processed but I prefer not). PhotZoom Pro say their prog can do it - so having read the manual I've asked them to explain - if PZP can indeed achieve the aim I'll let youz all know. Thanks - much happier now than I was last night worrying about all this. Now I just have to take those 300 (usable) soccer shots a day - simple.

Agree with Gordon, but are you sure that the images to be on the server are to be printed at 12x8"? I mean for some uses to have large files for printing, small pics to put on the server would be more natural. Usually we talk about MB (megabytes), except in telecommunication where transfer speeds are commonly in megabits/second, Mbps (confused?) It would probably be good to make sure that they mean megabytes and not bits.

 

Kelly, you forgot that many machines used non-8 bit bytes ;-)