I have a nice locomotive engine I found in SketchUp that has a very poor texture map.  The details are horrible.  Can I redo this map at a higher resolution in photoshop?  It's a simple design and I can blow up the existing map and redo it at a larger size and resolution.  What is the max size for a texture map in Poser?

There isnt one as far as I know. If you go bigger than 4,000 x 4,000 or so I run into memory issues.

What size is the original map ? 

512x512 is a good size for background things in the far distance

1024x1024 is a good size for medium background size objects

2048x2048 is a good size for screen size objects

4096x4096 is the max size per material group => for close up or detailed work.

Example:

You can use a 4096x4096 for the face material.
Another 4096x4096 for the body matarial , etc.;... ... ...

Or? As the face is a lot smaller than the rest of the body.
A 2048x2048 map for the face and a 4096x4096 for the rest of the body
Or a 1048x1048 for the face, a 4096x4096 for the rest of the body, and a 512x512 for the lashes.
Just examples.

A HUGE object, you can cut into more material groups if you need them.

Yup, as Vilters said...also make sure that your UV mappings aren't the problem. Good textures cannot solve poor unwrapping.

My computer can't handle a bunch of textures at 4000 x 4000. If I have only a couple items in the scene, it's not a problem, but when rendering a full scene I have to go and resize all of the textures to no longer than 1024 on the longest side.

@Acadia

Does reducing the bucket size help you with your memory problem?
It should.

Well, now you guys have me wondering...

Q: Any real difference --in render quality, or memory usage,-- between simply lowering the Maximum Texture Map Size in Poser's 'Render Settings', versus rescaling the original map in Photoshop or other external app?

Posers render "PREVIEW" settings only scales the map for preview. NOT for the final render. The slider says it: "Preview texture resolution".

The map used for rendering is the map resolution you import in the material room.

So to answer your question: changing this slider has an impact on the preview quality, but has NO influence on the final render outcome.

Render time, memory usage, render quality will all stay the same for the final render.

"Max texture size" is in the "FireFly" tab, not the "Preview" tab, the slider says "Max texture size" not "Preview texture resolution".  At least that's how it is in P6, I would be surprised if they had removed "Max texture size" from later versions.

Every question should include the Poser Version  and OS.

Sorry Les, I never had P6, but jumped from P5  to P7, then P8 and PP2010.

Sorry, you are right, vitters -- My Bad! 

Yes, the question was in reference to the map scale slider in the Firefly Render Settings in P6.

Kinda surprised to see that one was subsequently removed.   I use it quite a bit during test renders as it does appear to greatly reduce system demands & speed the process along.    But... I've never actually compared two side by side, so... now I'm wondering if I've just been kidding myself.   DOOH!

Well, with the Windows Task manager you can follow the memory load during a render and measure the difference between a low and a high setting in P6.
Ctrl+Alt+Delete and run in foreground monitoring CPU and Memory load.

That and bucket size changes could reduce memory load if needed.

Reducing Max texture size would reduce render quality.
Reducing the bucket size would have NO impact on render quality outcome.

Quote - @Acadia

Does reducing the bucket size help you with your memory problem?
It should.

Nope.  Tried all kinds of things.  It's either hide stuff and render a bit, then unhide and hide other things and render a bit and reassemble in PSP, or resize the textures.

Sorry if this is an obvious question, but if I redo the map at a larger size with more detail and keep it at the same aspect ratio and position, when I replace the old map with the new one it should increase detail. 

Yes, but maintain aspect ratio.

Not knowing what programs you use; You can always check your mapping in UVmapper free.

Poser 7 and up use a different texture cache mechanism during the render where texture size does not matter too much. (It uses a predetermined amount of memory). That is why the max texture size box was removed from the firefly settings.

Max Texture size in the Preview settings influences how much memory Poser uses for textures in the preview mode. Reducing that gives you more memory. Higher gives you better preview quality but reduces the amount of memory available for the rest of Poser

So for Poser 7 and up you do not need to lower the resolution of texture maps

Thanks vilters.  I'll check in UVMapper and then get to work in photoshop.  What file format is best for maps?  I've heard Jpeg can cause artifacts. 

jpg is pretty common. You are only openinng to view the jpg , not really recompressing it so you wont intriduce artifacts. I save the original image as png or psd as layers.

Thank-you wimvdb - for the explanation of why the Max Texture Size was no longer relevant.

     Another option for texturing large models economically is to use asymmetrical seamlessly tiled images. And it's OK to also use a non-tiled image on the material, for example overlaying a displacement map giving rivets and weld seams on top of a tiled image of wrought iron.  Most of my models are too big to even consider using a single (non-tiled) map to texture the whole model.

     If you see a blurry smear on the model when rendered, but only in a few places,  it may not be due to small texture image size;  the model might have a highly acute (sliver or needle-shaped) triangle in the mesh.  These are notorious for causing UV mapping distortion.

     I seem to recall reading that P8/PP2010 can use maps of twice the resolution of earlier versions of Poser.  Can anyone either confirm or deny this?