megabytes and ppi question

[crockny]

HELP! I'm entering a photo in a contest - they want 300 dpi (which I assume is ppi) and to keep the emails to 5mb ... my photo is 6.15 megabytes, 5184 x 3456 @ 300 ppi - what's the best way to meet the requirements without affecting quality ... I'm still not quite getting all the relationships ... I usually resize without resampling ...

[kcoppock]

If they're giving you a 300dpi requirement, they should be giving you a physical size as well. Preferably they should just give minimum pixel dimensions. With yours (~18 MP) you could either just resample it a little smaller (say 5-10%, Bicubic Sharper), or you could simply save as JPG with a higher compression. The compression will obviously compromise quality, but it may or may not be noticeable just to get it under 5 MB. Personally, I would go with resampling it to a smaller size.

[crockny]

Oy - How come when I look at the details in Bridge it says 6.15 MB but when I open it in CS4 at the bottom it says 51.3M? What's up with that?

[Doug Sundseth]

The number when open in PS is the size of the fully-expanded file (24 bits/pixel if using an 8-bit image).

The number in Bridge is the space on disk, which is normally significantly compressed, especially with a .jpg.

[crockny]

So how can I tell how many megabytes the file is when I'm reducing it in CS4? I don't see this measurement. So I reduce my image as per kcoppok's suggestions and don't know how many mb's until I save it and look at it in Bridge, I've reduced it three times and it's still too big -- there must be a better way ... are there any tutorials on this stuff? Also if I reduce the file and save the jpeg repeatedly am I degrading my image? I need to submit this tonight ...

[kcoppock]

As long as you're saving a copy, you're not going to further degrade it with multiple saves. If you're working from a JPG, and saving it again (compressing it further), then yes, you'll degrade the quality.

You can either just use trial and error to get it right, or you could try using Save for Web and Devices, which will give you a close estimate of the final file size in the lower left corner.

[teaking]

I have to question how anyone can request a 300 dpi image without giving dimensions and then give size limits all images will.vary in size due to content and information. If I were you I wouldnt mess about with resizing untill I got confirmation about image dimensions from them. You could save your self alot of work.

Its possible though as a lot of jpegs on a 12mpx point and shoot on fine will be just over 3mpg full size so im assuming its your image dimensions. Even a 300 x 300 pixel image can be 300 dpi I think its them not being clear enough

[crockny]

I know it seems weird to me too -- but I had a close deadline so I just reduced the big file by 75% and sent it in ... hopefully my photos qualify ...

[kcoppock]

:O

Reduced it by 75% or to 75%? Just curious.

[crockny]

Oops - TO 75% -- good catch ... still a rather large file ...