Image streaks

[Bundie]

Hi Guys,,

I just finished rendering this image, put it into photoshop for post and ended up with a whole bunch of streaks happening. I didnt realise while I was tweeking in PS due to the direction I was sitting with the monitor.
Does anyone have any suggestions as to why this is happeninig? is there such a thing as tweeking to much in PS?? I rendered the image at 2000x1080, is that to small? could it be my render passes and how the mix with the original render? ( it was my first try with render passes, so could be over tweeked

any help would be greatfull?

thanks

[Froggit Jake]

When you say streaking, are you referring to the banding on the walls where it appears to show a spectrum of colours as opposed to a gradient?

If so, that could be an issue with how you compressed it for taking into photoshop, i.e gifs only allow 256 colours, jpegs allow 16.77 mil, and RAW allows whatever is captured i believe.

Try saving the renders in different formats perhaps, and if that doesnt work, maybe someone else here can offer an explanation.

[bobman]

i would personally use .png its a more widely used format and can be uploaded pretty easily into photoshop without plugins or anything i would also try to stear clear of jpg format in general when doing renders

[Bundie]

yep, its the banding im refering to, sorry didnt know how to explain it to well.

I saved the render into a .tiff at 8 bit to bring into PS, but then saved it as a .jpg to upload to the web and use as my wallpaper. Ill double check when I get home if my image inside photoshop has the same banding before I saved as, I believe it does, but not as much as when I save as a jpg

would you recomend saving the render as a .png, working on it in PS and resaving the final render as a .png again? is that your saving workflow?

thanks

[Froggit Jake]

We've been having a few lectures on this sort of thing at university at the moment, you should bring into PS as the best quality image you can, or at least one that uses lossless compression, so the tiff. is okay for that because it retains each pixels value.
I think it's just the export then, so trying a png or a higher quality jpg, could be the answer, stay away from gif though haha. if its just for a wallpaper, jpg or png should be appropriate though, but there are ways to embed tiff images, though a little more complex than jpg's and png's... How to embed TIFF files in HTML documents

I guess its just to remember, if its going to be behing text and other images then the banding shouldnt matter if you can get it less severe, but perhaps if its going to be downloaded to be viewed on its own, have a high-quality tiff alternative?

All i can think of at quarter to 7 am

[MrTom]

Originally Posted by Bundie

...I saved the render into a .tiff at 8 bit to bring into PS...

.....and you're surprised it looks like that?

A little explanantion.....

• A 1 bit image means 2^1.....or on/off or 2 colours....or black/white.
• A 4 bit image means 2^4 (2x2x2x2) = 16.......colours.
• An 8 bit image means 2^8 (2x2x2x2x2x2x2x2) = 256 colours.
• A 16 bit image means 2^16 = 65536
• A 32 bit image means 2^32 = millions

So saving at 8 bit is not really that much better than saving in gif format.

Your 8 bit image is really divided into 4, RGBA.
Each of these channels must only have 2 bits to control it.....8(bit)image has 4(channels) so each channel must be 2 bits.
8=4*2

From above 2 bits = 2^2 or 2*2 which is 4.

Therefore saving at 8 bit means you have limited each channel (RGBA) to only 4 different shades of each colour and 4 shades of alpha (transparency).

Saving at 32 bit may seem a bit excessive but there's a reason behind it.

As you know there are only 3 colours that we use to create every other colour......Red Green and Blue. Each colour can range (In the Max colour swatch), in shade from 0-255 giving 256 different shades in total.

If we look back, 256 is equal to 8 bits.
Apply that for each colour....so

• Red = 8 bit
• Green = 8 bit
• Blue = 8 bit
• TOTAL = 24 bits.

Add in an alpha (transparency) channel also at 8 bit and........

....you get a 32 bit image with millions of colours and transparency.

Froggit Jake is right in saying you start off in PS with the best quality you can get.......stands to reason really. It's very easy to remove information from an image, but extremely difficult to add it.....in fact it's impossible to add it exactly as it should be.....a good guess is the closest you'll ever get, the more expensive the application you use the better at guessing it will be.

If you don't intend to use alpha channels (produced via render pass) then saving an extra 8 bits of info for it seems a waste of time, but its always better to save too much info and remove some in PS than not have it and need to introduce it....so whats the conclusion to all this?

Save out at 32 bit. That will give you 256 shades for each channel rather than 256 shades total.

Hopefully you can apply this to a 48bit image and see that it would give you 2^12 colours per channel........

48bits / 4 = 12bits per channel.
12bits = 4096 shades per channel, as opposed to the 256 we work with in Max.

A 64bit image involves numbers too large for my tiny brain to even comprehend....let alone explain......

And if that doesn't confuse you then I must try harder....LOL.

Regards.

[Froggit Jake]

Well confused Mr Tom, congratulations

I remember the human eye as only being able to view around 10 million colours, so an 8-bit per channel for red, green and blue ought to be enough, giving out 16.7 million, but maybe its to do with the way the software interpolates the colours it has. Either way, try the 36-bit image with a 12-bit transparency too, so that it has the most you will ever need. If you need more... then i dont know, ever :P

[MrTom]

Originally Posted by Froggit Jake

.....Either way, try the 36-bit image with a 12-bit transparency too, so that it has the most you will ever need. If you need more... then i dont know, ever :P

You shouldn't even need to go as high as 48bit for general renders really.

That kind of information is normally only needed for high-end productions that ultimately end up being used for film.....and pretty big image frames. 64bit being used as the equivalent of 70mm film for IMax etc.

It's all relative, but for most situations and especially anything used with digital media, 32bit is enough.

When all said and done digital images are just a bunch of numbers.....how many numbers you allocate to those images will define how good/bad it looks, reflected in the respective size of the resulting file.

When you render an image in Max, all the information is there for the taking....it's done the number crunching....it's then down to the individual as to how much of that information you want to store with the image when you save it.....which of course depends on what you intend to do with it, (Hence the option to save as many different file types).

Regards.

[Bundie]

fantastic information, confusing, but at least I know to use 32 bit

cant wait to go home and re render the scene so I can save it as 32bit

I have saved another render as a 32bit, but when I bring it into PS, it seems I cant duplicate the layer??? and some of the icons are greyed out???
If I then save it as say a 16 bit, it enables all those icons.

anyone know what im doing wrong?

[MrTom]

Normally an image that won't duplicate has indexed colours, it will say "Index" as the Layer title (as opposed to "Background") and should be locked.

If you change the mode (Image>Mode) from "Indexed Color..." to "RGB Color..." the Layer lable will change to "Layer 1" (and should unlock) and you can edit as normal.

This usually only happens with gif files though, but I guess it's possible with other formats if you've saved them at 8bit....I couldn't say for sure, I've never saved anything but a .gif @8bit.

Regards.