Very Large Maps, is it a problem?

[su_liam]

* In photoshop (and i think GIMP) you can set the bit depth of each channel. Going from 8 bits/channel to 16 or 32 greatly increases the file size and processing time. For map-making you will not regret leaving it at 8 bits/channel.

Can you really? Do tell. If I could work out how to do this, it would be enormously helpful. I'd give a lot to be able to edit the elevation data in 16- or, better, 32-bit grayscale and apply gradient maps and lighting effects(I wish that was a layer effect) in 8-bit RGB.

EDIT: That, by the way, wasn't intended to be as smarmy, smug and generally asinine as it came out. I just really, really want to know how.

[jwbjerk]

Can you really? Do tell. If I could work out how to do this, it would be enormously helpful. I'd give a lot to be able to edit the elevation data in 16- or, better, 32-bit grayscale and apply gradient maps and lighting effects(I wish that was a layer effect) in 8-bit RGB.

OK.



To be clear you set the bit depth for the document as a whole. 32-bits was added recently CS3 or CS4, but the 16 bit option has been around at least for several versions before that.

[su_liam]

Okay. I gotcha. I usually do my HF editing and color texturing in separate documents anyway, when I don't just use Wilbur. Interestingly 32-bit was really crashy in the windows machines at school, but seems more reliable on my mac. Adobe and Apple get along so well inside the computer its a little odd how hammer-and-tongs they've gotten out here in the world.

[a2area]

I don't know about GIMP, but in photoshop zooming to 100% means that every pixel on your screen represent a pixel in your document. I.E. there's a one-to-one correspondence. DPI or PPI is irrelevant to how "100%" looks on screen.

Actually, you are right.. which means that PPI is totally irrelevant in relation to document fidelity unless your image is resampled as well. Still.. the original point remains.. if a document is 100 pixels by 100 pixels... then it remains so whether it's set at 1ppi, 10ppi or 100ppi etc..

[Hai-Etlik]

Actually, you are right.. which means that PPI is totally irrelevant in relation to document fidelity unless your image is resampled as well. Still.. the original point remains.. if a document is 100 pixels by 100 pixels... then it remains so whether it's set at 1ppi, 10ppi or 100ppi etc..

It's an option to choose which behaviour you want: View -> Dot for Dot

[Natai]

Here's an excerpt from a post I made in this thread Question on huge size images

The image is 20122x11634 @ 450 px/in. The PSB file is about 3.7GB saved, and PS consumes around 7.75GB in memory while I'm working with it. So tilt's point is a good one - go with 2-3 times the amount of RAM relative to the saved file size.

So, bottom line if you're working with files larger than about 1.5GB, you will probably benefit from upgrading to 64-bit. Just be sure to keep in mind what Redrobes posted - you're entire system has to be 64-bit, the CPU, OS and the application.

That thread might be useful as it contains some good information about RAM, memory pointers, etc. And just about all the posts are referencing maps at the scale you were talking, 20k x 10k and up.

[Antheon]

Of course the dimensions will stay the same. ppi isn't pixel-related, it just says how many pixel can be filled within an inch of length. So, if I want a document with 100 pixels in both directions, it will still be 100 pixels, regardless of the ppi selected. Also the file size stays the same. Working on the screen it doesn't matter what ppi you select as you are working with pixels and not inches/centimeters/millimeters/whatever. But if you do it the other way around and configure the "real" size of the image the pixel dimensions will change of course. It's simply because the pixels used for a document depend on the "real" dimensions. Open a new document in any graphic program you like, may it be the GIMP or PS or whatever, and create a 100x100@300ppi. Then do the same at one pixel per inch. Both documents seem to have the same size, you say? Of course they do! You entered the same pixel length. It doesn't matter if there can be 100px or 2px within one inch, 100px still are 100px. The difference is, that the first one fits perfectly inside this inch and the other on is 50 inches long. If you change the dimensions in your ruler to inch or something else, you might notice the difference between both examples. : )


Antheon
hoping he doesn't talk nonsense ...

[a2area]

Hey, stop repeating me Antheon! (0:
Now which is heavier.. a pound of feathers.. or a pound of lead? he he..


actually what i'm still going on about (like a senile old man) originates from an earlier post where someone said

but just wondering, cause if your doing a 12,000x10,000 at 72 dpi thats a lot different than 300 dpi

... in reality there is no difference in your working environment.


I have no idea what bit-depth is for however.. although have often wondered.. i suppose i should look into it at some point.

[jwbjerk]

Hey, stop repeating me Antheon! (0:
I have no idea what bit-depth is for however.. although have often wondered.. i suppose i should look into it at some point.

Bit depth controls how many different colors a channel can have. For instance an 8 bit greyscale document can have 256 different "colors": black, white, and 254 greys in between. 256 is a number that requires 8 bits to store. With 256 levels each of red, green and blue, you can mix ~16 million distinct colors -- weather or not your monitor or eye can distinguish them.

A number that takes up 16 binary bits is much larger-- you get 65,000+ levels of grey in a 16 bit greyscale document. And some trillions of possible colors in RGB.

[Antheon]

Yeah, I know that I was repeating you but it seemed that there is a misunderstanding about ppi in the workflow. : )
As for the bit depth it defines the colour palette you can use. 1-bit simply means 2^1 colours - therfor we have black and white. With two bits we can apply four colours: black, white and two greyish ones. With eight bit we do have 2^8 = 256 colours. I think we called that VGA back then. With 32-bit at our disposal we do have 4.2 billion distinct colours but often the program does only use 24-bit and 8-bit for alpha etc. Up to 48 bits we already have 281.5 trillion colours and there are graphic cards able to go even beyond that and support 64-bit colour!


Antheon
ready for Mr Sandman

EDIT:
Argh, I was too slow. *laughs*