Small JPEG's

[craiggorton]

I'm just curious- why are my renderings (saved as jpeg's usually) so small (file size)?
I think it's a good thing- very easy to email. But if I capture my shaded Rhino viewport, it's much more kb's than a similar sized rendering. Why is that?

Thanks

[joe_b]

Re: Small JPEG's

I'm not sure - could be compression techniques?

[drybarr]

Re: Small JPEG's

yeah the JPGs from vray look horrible. I save the testrenders as png and finals as tif

[Micha_cg]

Re: Small JPEG's

PNG compress lossless, so why not use it allways?

[dalomar_cg]

Re: Small JPEG's

I'm to pngs myself. Better compression + integrated alpha. For finals I try to save as either hdrs or exrs. I think exrs are better when it comes to file size.

[drybarr]

Re: Small JPEG's

PNG compress lossless, so why not use it allways?

because I had no idea it was lossless and had an alpha will use it from now on.

small meaningless correction to my previous post - I used tga and not tiff, vray doesnt even export in tif if I remeber correctly now..

[craiggorton]

Re: Small JPEG's

I was about to report that I have been looking more closely at jpg's since I'm starting to do more post-processing, and I agree, the jpg's are not good.

But am I doing something wrong with png's- when I open them (windows viewer or PS) the background is gone. There's no clouds and sky where the alpha is. I do a lot of yacht renderings where you can see a lot of the background image (sky) so this is important. An accurate horizon is crucial, so I can't wait for infinite groundplanes.

So I tried tga and that works well. Any reason to use png instead of tga?

Thanks,
Craig

[dalomar_cg]

Re: Small JPEG's

Yea the png thing is the integrated alpha channel that I was talking about. The vray plane is on its way, but for the time being I just use a really large circle surface thing. Targas do work well, and I used them allot when I worked more with max. The thing about them is that the windows picture viewer can't read em, which is annoying when I just want a quick preview or something. IMHO targas are inbetween pngs and hdr/exr in that there good, but because they can't be viewed easily and are bigger than pngs then in my book its not that good for everyday use, and once I'm bumping up the quality why not go all the way to hdr/exr and preserve the float point data.

[craiggorton]

Re: Small JPEG's

Ok, but why does the alpha channel of the png clear that area? I like to use windows viewer too, but it seems like the png output is not saving any data from the background (other than the fact that it's the background). Is this really intentional?

[dalomar_cg]

Re: Small JPEG's

yes this is intentional, remember that the png is reading the info from the alpha channel not the rgb. It just so happens that we set an image to be a background, but the png doesn't care. I agree that it is annoying (when it matters I might save as a jpg or something). Maybe we should have an option to disregard the alpha output when saving a png...you could sign me up for that one.

[Micha_cg]

Re: Small JPEG's

PNG workaround: I use the great image browser XnView (www.xnview.de) : I select an image and copy it to the clipboad and at photoshop: create new image and past from the clipboard. Works well, the background is visible.

[craiggorton]

Re: Small JPEG's

Either add an option for the background in png, or just don't compress the jpg.
I have to have others (my boss) be able to look at renders without a special viewer. I'm trying to avoid a many steps as possible when getting a render from the frame buffer to completion, I don't want to cut and paste backgrounds every time.
Why would you want to lose the background from the png anyway? You can always save an alpha channel separately. Wouldn't that be better?
Again, I think uncompressed jpg would be good.

Craig

[joe_b]

Re: Small JPEG's

Again, I think uncompressed jpg would be good.

An uncompressed jpg is a bitmap - so you might as well just use a bitmap. It also won't cut out the background.

[craiggorton]

Re: Small JPEG's

That's what I needed to hear! Thank you (and excuse my image filetype naivete.)

[joe_b]

Re: Small JPEG's

np - its hard to remember all the differences between them all. I agree it is kinda irritating that the background is just assumed to be on the alpha channel