[Turokess]

Okay, I've got this really large file I'm working on and there's some stuff going on I don't understand. To begin with, my original file is a CMYK psd, 14513 x 5850 at 300dpi, and it has to be that big too. I have to do several different versions of the image, changing some elements, time of day, etc. The trend is, the file gets bigger with each new version. I haven't been adding new layers with each one, but changing what is on the layers accordingly. My last image topped out at 462mb, the previous one was 391mb. This new one, built from the 462mb one, has just reached 631mb. I think it has even less layers than the 462mb one. So why on earth is it getting so big? Wouldn't it stay around the same file size? Does it have to do with about of color and surface area covered on each layer. My computer is handling it so far but I've had to tell it not to keep any history. I'm afraid it will get to the point where I can't work on it and I have yet another version to do. Well, if someone can tell me about the workings of CMYK and what affects the file size so much would be appreciated.
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[Chruser]

I made some experiments with a 2000x2000 (72 dpi) canvas to find various results. It seems that the amount of colours used defines the size of the picture a lot more than their actual area. Gradients or soft brushes would clearly add a LOT of value/colour variation, and soforth increase the memory usage significantly. I've never experienced any such thing as photoshop actually LOGGING old junk for no reason just to increase the file size. .psd is a good format in my experience. I illustrated some examples for you (call it abstract art if you like ) as mentioned above:



(211 kb, low colour variation, high area)



(235 kb, same colours, more overall areas, no large image size difference)



(370 kb, more colours, some area increase)



(6,482 kb, three gradients applied on top of previous image, one of which is transparent, all containing a large range of colours)



Note: My server is getting wiped tonight for a complete reinstall of Linux. If the images don't work, I'll make sure they do later on. Anyway, I'd love to make a 4096x4096 px (16.7 million pixels in total) canvas where every single pixel gets its own colour out of the 24-bit palette assigned to it just to check the size of that, but I haven't figured out a way to do that yet.

[Strawberrysauce]

Just the way it goes im afraid, more layers or content on the current layers = bigger file but does your file really have to be that big? If its for a print banner or something can you not work at half resolution?

I remember a couple of years ago producing a huge stand, something rediculous like 20ft high for a local company, the graphics were quite fancy so it was a photoshop job and the resulting file was over 2gb and that was only with around 30 layers or so.

It took the G4 about 15mins to open and save it

[math]

wasnt there some way to split some pic up in many smaller pics? some idea from me...u could add like 1 red(for example) pixel on the borders of each smaller pic, so if u put them together u exactly know how to.
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[Turokess]

Hey, thanks for the help everyone. I worked with my files a bit and got the size back down through some of the more paint covered layers. Yeah, it's a pretty big size; the reason is they are going to be 21' x 8' stage backdrops. I just got the last of the four done an hour ago. Yes, we use old Mac G4s at work. I hate them. It takes mine over twice the time it takes my home PC to open and save the files.
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[cheney]

The image is going to have a large file size due to the pixel size. The number of layers you use in this image is mostly irrelevant to the file size. What is important is what is contained in each layer and channel. If you are creating complex textures that fill large areas of the image your file size will be incredibly huge. Consider the following:

I have this former website layout made to look like a book with photos. The graphics for this site were created using only three PSD images. The primary PSD image contains approx 2500 layers. Saved as a PSD the file takes up roughly 65mb of space, but opened it takes up about roughly 750mb of scratchdisk space. I used 5 layers for each text group to give a more naturally saturated look for added realism. Each layer contains very little data, so they don't add up to much.

The heaviest image I ever created was a post called "23" for my brother. This image contains only 20 layers, but when saved as a PSD it is over 2gb file size. When it is opened I am estimating it requires about 40gb of scratch disk space, but this is a gross approximation that is diffecult for me to determine. This image most entirely a texture study where numerous texure elements were created in both layers and channels. There is not much to the image, so each texture layer fills an enormous area.

Both of these are available on my website as examples if I did not explain them well.
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