How do I prevent banding with the PS gradient tool.

[AndrewEllinas]

I take photos on a 10D and use Photoshop CS.

Occassionally I like to fill in white skies (and we get a lot of them at this time of the year in the UK) with a faint blue gradient using the Photoshop tool.

How can I make the graduation from light blue to transparent as smooth as possible and prevent it from 'banding'?

[Scottes]

It's been a long time since I've done this, so maybe someone will come up with a better way...

I would create another image on the desired dimensions and work in 16-bit to get more levels of blue - remember that 8 bit gives you 255 blues - so if you go from a mid-dark-blue to a mid-light blue you're down to about 64 levels.

Create your gradient, reduce to 8-bit with a dither to reduce banding, and then blur. Cut and paste that into your desired image into a new layer with a blending mode or modify opacity to get final desired effect.


Option 2, take many pictures of blue skies and cut and paste them in. Much more natural. Get up somehwere high and spin 360 degrees taking pictures along the way - this way you'll get the sunlight at various angles to better match the lighting in the finished product. Take the pictures at a natural angle - ie; don't shoot straight up - to once again get more natural lighting to match.

Digital film costs nothing - do this every time you go out and soon you'll have hundreds of various skies for a library.

[AndrewEllinas]

Thanks. The sky library is a good idea.

[PacAce]

AndrewEllinas wrote:
Thanks. The sky library is a good idea.

I've used gradient colors of all sorts many a times and I've never come across a case of banding. Are you sure you have your video setting set to use 24 bit or higher (true color)?

[john_houghton]

Yes, the answer is to work in 16 bit mode as far as possible - now much easier with PS CS. A simple plain gradient can look rather bland and, well, fake. You should always apply a small amount of noise to match the noise in the original image. This will also help eliminate any suspicion of banding. For wider views, such as panoramas, you should also consider giving some left to right variation by placing two slightly different gradients on different layers, with a mask on the top layer to control the transition between the two.

John

[ssim]

I was putzing with this very subject last night.

I have developed a small library of sky backgrounds that I use. These seem to work pretty well.

I was playing with the Filter-Render-Clouds menu choice last night and came up with the following:

http://www.pbase.com/image/23835064.jpg

This to me looks better than the gradient ones that I had come up with.

[PhotoAZ]

Simple, Think of it like film. Since the graduate is a color graphic and not an image all you do is add Noise. Go to Filter/Noise/Add Noise for this.

A grapic is not the same as the image and just like with film and grain, noise is needed for graphics to blend with images. The same is true if you are placing two images into the same image that where done by differant cameras or two differant ASA settings. Adding a little noise will balance the images. A good trick is to use layers and just add the noise to the layer and not the entire image.

[Scottes]

Ssim, I can imagine that this looks better than gradients, but it still doesn't look right. The lighting on the clouds looks flat, while the building is receiving light at an angle. With a sky library you could do something like this:

http://nexus.int.itsanadventure.com/postimages/MagnoliaCove_0231.jpg

Certainly a lot more natural looking. The angle of the sun is correct, color temperature is correct, viewer's angle to the clouds is quite close to correct. Not quite perfect, but then again I know what I did to this image.

[ssim]

I agree that the cloud library works better but I was only showing what else was possible.

I took the liberty of grabbing your picture and putting some of my clouds behind it.

http://www.pbase.com/image/23892464.jpg

What do you think. This will only stay on my pbase site for a few days.

Sheldon

[marcel wouters]

Impressive!
But it's really not the good sky for this pic!
You need a low sun with a red yellow cast of late afternoon as in the original pic!

[Scottes]

Sheldon, your clouds *do* look good, but as Marcel said - "Not with this pic"

My pic of the cove was taken about 20-30 minutes after sunrise, and the sun was kinda behind to the left. In my clouds, the sun is obviously low in the sky, and more or less off to the left. Both pics were in Raw mode, so I could adjust the color temperature to match naturally. The picture of the clouds was taken at the same angle as the picture of the cove, so the clouds gradually darken and blur as they get further away.


As pure and simple clouds your clouds look great. They're very natural looking, but they don't match this picture.

Your clouds look like you shot the camera straight on at noon-time. The edges of the clouds "closest to you" are brighter, making it look like the sun was behind you. There's no gradation near the horizon. They're too big for the image.

When faking an image like this you must take care to match lighting and angles and colors of both images. Otherwise the differences stand out to the eye. Someone might not be able to tell you what's wrong, but the eye will know that *something* is wrong. My clouds aren't perfect, but I bet they'd pass the inspection of most non-photographers.

[SWPhotoImaging]

I have to agree with Scottes. Lighting angle difference is the surest way to make even untrained eyes think something is amiss in hybrid or manufactured images.

Even out-of-proportion clouds, or unrealistic cloud shapes can be made believable by proper lighting and coloring, matching the angle and color of the sun.

I can only hope to someday achieve the level of expertise that Scottes obviously has in hybrid image creation, but even in his excellent rendition, I can see that the cloud lighting angle was mildly skewed from the landscape lighting angle My first impression is "WOW!, great picture, awesome lighting, wish I was there!"

Unless you are being asked to notice the clouds and lighting, as we are being asked to here in this thread, you'd stay with the first impression and never notice the very minor lighting angle difference. You have to be specifically looking for how well it's matched to even detect any minor variation.

It's the ones where the sun angle makes the landscapes orange or red, but the clouds show no orange or red, that your mind automatically says "fake" even before your eyes figure out why.

By the way, all of you are far above my skill level with PS, including Sheldon with his perfect clouds in pristine blue skies at all hours of the day.

I haven't graduated to attempting to create things yet, I am still working on color and image tuning.

Thanks for the great examples and learning material.

-Gizmo-

[Scottes]

sdwike@hotmail.com wrote:
I can only hope to someday achieve the level of expertise that Scottes obviously has in hybrid image creation,

Actually this was quite simple to do. I used RAW mode and exposed twice - once to get the ground good, and then I overexposed to get the original sky blown out. I put each image in a seperate layer, good image as background.

On Layer 2 (overexposed sky) I magic wand selected the blown-out sky and deleted it. Overexposing this makes it simpler to select this way. I then used hand erasing to get the edges correct. (Doing this between branches on a fall tree is TOUGH - try to avoid this, or erase trees on the horizon.)

So Layer 2 now consists of an over-exposed ground and emptiness where the sky was. Select the sky section with magic wand, and fill with black, no anti-alias or feathering. Selection... Inverse and Delete the overexposed ground. Layer 2 is now a black blob shape matching the shape of the sky.

Magic wand select this, flip to Layer 1 (background). Hit Delete to remove the old bad sky completely - make sure it fills with white. Layer 1 is now just the good ground.

Add a Third layer, the good sky. Flip back to second layer (the black blob shape) magic wand select this shape. Flip back to good sky layer, do Selection... Inverse...(to select non-sky) and Delete to get rid of everything that is not sky. Now I have a chunk of good sky and nothing else on layer 3.

Basically I created a black blob shape matching the sky. On the good sky layer I made a selection matching this shape, thus getting good sky in the same shape. On another layer, the ground, I selected the inverse of this black blob shape, thus getting good ground in a shape NOT matching the black blob shape. Merge the two good layers and you have a single image - good sky with good ground.

Hopefully you get an image with no seams. You might want to play around with feathering the edges, or overlap them in some way (make each 5 or 10 picels too big) and do judicious erasing along the edge. Play with opacity on the sky layer vefore merging. I could go on and on.

But the most importatnt thing is to make sure that the two images "match" in color and light and angles. If they don't, the greatest Photoshop Guru in the world will still produce an image that doesn't look right.

PS: There's a thousand ways to do this - this is just the basics.