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DPChallenge Forums >> Stock Photography >> Upsizing...I'm confused. 53 MB or 6MB?
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 09/20/2007 03:50:51 AM · #1
I'm making this new thread so I won't hijack the Alamy thread.

idnicexplained about upsizing for Alamy.

the photo has to be 5300 pixels on the longest side and a minimun of 48MB at 300 DPI.

OK I'm clear on that and started to edit a shot this morning just to test what quality I would be left with. That's not too bad at all!
Im PS >image size< it said my shot was 53MB at 240 DPI. OK great!

But then I uploaded it to an online professional printshop (allways use them, very good quality) just to see what it would look like on a 20-30 CM photo. My file turned out to be only 6 MB.

So that is what's confusing me. What is it? 53 MB or 6 MB??

I also saved it as a maximum quality JPG file. Should I save it as a different file for Alamy and other stocksites?
 09/20/2007 04:31:49 AM · #2
I believe that you would have to save it as a TIFF
 09/20/2007 05:07:19 AM · #3
Your 8 bit 48+Mb file should be saved as a Jpeg for Alamy. This will give a file size in the region of 6Mb, maybe more or less depending on the content :)

Message edited by author 2007-09-20 05:08:00.
 09/20/2007 05:15:06 AM · #4
Originally posted by Puckzzz:
So that is what's confusing me. What is it? 53 MB or 6 MB??

You're confusing image size with file size.

The image is 53MB; however, when you save it as a JPG file that data is compressed and only takes up 6MB. When someone like Alamy is specifying size requirements, they are referring to image size (the 53MB figure in your example) and not file size.

(incidentally, ignore the DPI stuff; it's just fluff that adds to some people's confusion and has nothing to do with image size in this context)
 09/20/2007 05:42:35 AM · #5
ah OK! thnx for the info!
 09/20/2007 05:43:51 AM · #6
Originally posted by Puckzzz:
the photo has to be 5300 pixels on the longest side and a minimun of 48MB at 300 DPI.

Where did you get the '5300 pixels' info from? - I just checked Alamy again and can't find this requirement. The only requirement I can find is the 48MB minimum size one.

Okay, this is what Photoshop gives you. On the bottom left of the screen the arrow lets you see various bits of info about the current image. Click 'document sizes' and that shows you the pixel size. You can see below it's the number on the left (17.2M).



Next the Image Resize dialog also shows the image pixel size, so I use this dialog to get the image up to the 48MB requirement, using trial-and-error. We're starting with 17.2M, I need to increase the dimensions until this is at least 48M.



Here you can see I've increased the height to 3400 pixels, which results in a pixel size of 49.7M (I just kept increasing the value until I got a pixel size greater than 48M). If you're upsizing like this in PS make sure you use 'Bicubic Smoother';


09/20/2007 05:47:11 AM · #7
Originally posted by Puckzzz:
I'm making this new thread so I won't hijack the Alamy thread.

idnicexplained about upsizing for Alamy.

the photo has to be 5300 pixels on the longest side and a minimun of 48MB at 300 DPI.

OK I'm clear on that and started to edit a shot this morning just to test what quality I would be left with. That's not too bad at all!
Im PS >image size< it said my shot was 53MB at 240 DPI. OK great!

But then I uploaded it to an online professional printshop (allways use them, very good quality) just to see what it would look like on a 20-30 CM photo. My file turned out to be only 6 MB.

So that is what's confusing me. What is it? 53 MB or 6 MB??

I also saved it as a maximum quality JPG file. Should I save it as a different file for Alamy and other stocksites?

You're in good shape.

Alamy wants a minimum 48MB uncompressed file size. You've hit that no problem. The 6MB file size is the compressed JPG you ended up with. At highest quality you're fine here as well. The only restriction Alamy has on JPG size is it can't exceed 20MB (I think - would have to double-check that number), and a 20MB JPG would be huge in an uncompressed state.

In both cases, your 53MB and 6MB files, are file sizes - nothing to do with image size which is usually refered to in megapixels (MP).

One thing I'm not clear on is the 5300 pixel longest side you mentioned. Didn't think there was any actual size requirements (it goes without saying your image will be large enough at the 48MB minimum file size). Generally your images will be around 5300 on the long side (could be a little less, say 5150, if the image has a lot of detail to it versus a lot of clear blue sky), but it's not a requirement.

Now after saying all of that, I need to revisit the submission guidelines again! :P

edit - I took too long typing while trying to eat breakfast. jhonan beat me to it I see. :)

Message edited by author 2007-09-20 05:48:57.
 09/20/2007 06:15:12 AM · #8
I think the 5300 was a ballpark figure mentioned on the other thread; without cropping I tend to upsize the short side to 3500, which gives me 50Mb or so, give or take.

So that 5300 is not a requirement, any more than my 3500 is; it's just a handy guideline to give you a starting point. I'm too lazy to worry about getting it bang on 48Mb and I find that aiming for 3500 gives me about the right size even with a small bit of cropping. I suspect idnic takes the same approach but happens to use the long side rather than the short :)
 09/20/2007 07:29:06 AM · #9
yeah that 5300 was something i read in the other thread. but i understand that is flexible.

thnx all for the great explanations.
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