CGTalk - Annoying jpeg filesizes, when "SAVING AS"

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Undseth

07-01-2003, 11:45 PM

Usually, when I save a jpeg form the Maya renderview, Maya outputs a jpeg file with 100%. (whatever that actually means in terms of compression)....

And when I open up these files in photoshop for cropping, and then saving as... as jpeg file again... the file sizes are simply great... and the quality is great too... Vague example; some ok canvas-size with filesize at 20-35 kilobytes...

BUT...

With other jpeg files, say directly from my digital camera with initial size up to say 1200x1000 something... the file size is initally about 400-500 kilobytes.

So I want to crop them, but when I save the cropped file, the file size is pretty huge (like compared to the ones I get from Maya) like 60-90 kilobytes... which is pretty big files I think.

Is there some magic thing with the handling of jpeg files, cropping and then saving as... ?

Even when I pull the slider to 0-1 compression quality for jpeg's, the file size is pretty huge (about 30 Kb).

I don't get this. Am I missing some thing here about jpeg files? Do I have to convert the jpeg file at some stage, before saving a jpeg file, with ok compression quality, and affordable file size?

Does this make sense to you?

bumskee

07-02-2003, 12:14 AM

hey undseth,

instead of using "save as" try "save for web" it will allow more control.
image size will depend on what the actual image is as well as the size and quality (jepg), so if you are working with jpeg, certainly save for web is the best option.

hope that helps, cheers,

Undseth

07-02-2003, 12:19 AM

Thank you!!!

I'll try that.

I just had the idea that by cropping an image to a smaller size and compressing it into a "simpler" jpeg file, the file size would automaticly get much smaller. But there seem to be a limit sometimes. Like lowering compression quality really really low, yet ending up with a file size of say 30 kb, when a "maya jpeg" could get cropped and end up as a 9 Kb file.

Ok, enough from me. I'll go check this out!

mOOb

07-11-2003, 12:14 AM

Im not entirely sure but i think it may have to do with the noise from photos taken with the camera. I did a test in pshop 2 pics each 400X400 one with a noise filter and one split in half with 2 colors. Both were saved at 5 quality the one with noise ended up being 135 kb while the one without was 10 kb.. it has to use more data to accurately represent the detail in the picture. I may be wrong though :)

Protoplasma

07-11-2003, 11:39 AM

the image size depends on the informations that are in images. (colors)
if you have 2 pics with the same size and there is a huge area with mostly one color in one of them - this image will be smaller than f.e. a photo in the same size. I don`t know what your rendered but in wips f.e. is mostly a monochrome bg. there is no noise in a rendering like mOOb mentioned. If you have a black area in a photo - there are several informations in that are not obvious. You can see it when you increase the brightness. A black area in a rendering is black.
I think that is why your renderings are smaller jpgs than your photos.

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