Photomerge problem

Grumpy_one

I didn't notice the problem until I saw the print. I was able to play with it to make the problem more appearant. Take a look


Here's the pic as I thought was ok. You have to look hard to see the defects. This is two photos merged with "photomerge" in PS CS3. The separate photos do not have, what I call "the global lines". I did manage to do a manual merge and no lines show up. Any ideas why photomerge does this?

Tango

did you check mark the "blend" option?

ziggy53

Were you using a polarizing filter?

Grumpy_one

ziggy53 wrote:

Were you using a polarizing filter?

no

AaronNelson wrote:

did you check mark the "blend" option?

yes

digismile

The fact that the banding is globe shaped is most puzzling. What I do see (or think I see) is a difference in exposure between the 2 photos. The rock on the left of center is much lighter and less saturated looking. The sky is also quite different right to left.

I have seen Photomerge create banding (but not this shape) when the images are significantly different in exposure and it makes adjustments to try to blend the images.

Do you see the bands in the individual layer masks? (you should be able to disable each photo's mask).

What if you get the exposures closer. Does the banding decrease?

And last, how much overlap do you have betweeen the images?

I'll be very interested when you find the answer to your question!

Grumpy_one

digismile wrote:

The fact that the banding is globe shaped is most puzzling. What I do see (or think I see) is a difference in exposure between the 2 photos. The rock on the left of center is much lighter and less saturated looking. The sky is also quite different right to left.

I have seen Photomerge create banding (but not this shape) when the images are significantly different in exposure and it makes adjustments to try to blend the images.

Do you see the bands in the individual layer masks? (you should be able to disable each photo's mask).

What if you get the exposures closer. Does the banding decrease?

And last, how much overlap do you have betweeen the images?

I'll be very interested when you find the answer to your question!

Overlap:


I did a manual merge and no banding that I can see.

Grumpy_one

The originals untouched




edit: well converted to jpg and file size shrunk down

ziggy53

I don't see anything that should cause that banding to happen.

Most curious.

Grumpy_one

ziggy53 wrote:

I don't see anything that should cause that banding to happen.

Most curious.

Me too, I love this feature!

digismile

Pretty big shift in color and contrast between the original and final. What color space did you do your PP in? Lab and back to RGB?

Grumpy_one

digismile wrote:

Pretty big shift in color and contrast between the original and final. What color space did you do your PP in? Lab and back to RGB?

No, just threshold and levels, then curves and sharpening.

pathfinder

Were these images shot in Manual mode with the same exposure settings and same focus ( manual focus)?

Grumpy_one

pathfinder wrote:

Were these images shot in Manual mode with the same exposure settings and same focus ( manual focus)?

I'll double check the exif, but I'm pretty sure it was manual mode, auto focus.

pathfinder

Panos merge best when the exposure is exactly the same from frame to frame. A stationary ( Non - AF ) focus is recommended also.

If the frames are shot in RAW, the RAW converter settings can all then be set to be exactly the same, which should help frame to frame consistency.

moose135

pathfinder wrote:

Panos merge best when the exposure is exactly the same from frame to frame.

Just to be clear, when I'm composing the shots, I should have the exposure level indicator the same for each (-1/3, 0, etc) correct? Not that I should use the same shutter and aperture settings for each shot, right?

jfriend

moose135 wrote:

Just to be clear, when I'm composing the shots, I should have the exposure level indicator the same for each (-1/3, 0, etc) correct? Not that I should use the same shutter and aperture settings for each shot, right?

No, you need to have the same shutter speed and aperture settings and ISO for all shots. Remember, you will have overlapping pieces of the image from one shot to the next. If you don't have EXACTLY the same exposure on each shot, then those overlapping pieces won't have the same brightness when you go to merge the different shots.

I put my camera into manual mode, adjust the exposure so it's proper on the left side of the image. Then, scan the camera from left to right and watch the exposure meter indicataor in the camera. If it indicates that other parts of the image are much brighter, then I may adjust the exposure for the brightest segment of the image so as to not blow highlights anywhere. Then, I take all the shots in manual mode with that constant exposure. Now, all the overlapping elements from one shot to the next will be exactly the same brightness. If I have to correct the overall image brightness a bit when I'm done, I do that after I've done the merge.

FYI, you also want the aperture to stay the same from one image to the next so that you have the same depth of field in each shot.

Grumpy_one

I checked the exif, I goofed. It was set on auto and the f stop changed. I thought I was on manual. I was all over the place as far as different lens's and different settings. I wasn't paying attention. Lesson learned. After looking at the streaks that photomerge left behind, it seems as though it was trying to take samples from each side and swap. It did it in streaks. Not sure way it choose to it in this matter, but manual mode is the way to go when shooting. When I merged the photo's manually, I adjusted the one photo to match the other and it was ok. Thanks for the help. Mystery solved.

Scott_Quier

jfriend wrote:

No, you need to have the same shutter speed and aperture settings and ISO for all shots. Remember, you will have overlapping pieces of the image from one shot to the next. If you don't have EXACTLY the same exposure on each shot, then those overlapping pieces won't have the same brightness when you go to merge the different shots.

I put my camera into manual mode, adjust the exposure so it's proper on the left side of the image. Then, scan the camera from left to right and watch the exposure meter indicataor in the camera. If it indicates that other parts of the image are much brighter, then I may adjust the exposure for the brightest segment of the image so as to not blow highlights anywhere. Then, I take all the shots in manual mode with that constant exposure. Now, all the overlapping elements from one shot to the next will be exactly the same brightness. If I have to correct the overall image brightness a bit when I'm done, I do that after I've done the merge.

FYI, you also want the aperture to stay the same from one image to the next so that you have the same depth of field in each shot.

One thing to add to this. In addion to shooting in manual mode so that the shutter speed, aperture, and ISO are held constant across all the shots of the pano, you also need to have a constant WB.

What I mean by this is you need to take the WB out of AWB and set it to something, anything. Set it to either a Custom WB or to one of the "built-in" WB settings.

Grumpy_one

Scott_Quier wrote:

One thing to add to this. In addion to shooting in manual mode so that the shutter speed, aperture, and ISO are held constant across all the shots of the pano, you also need to have a constant WB.

What I mean by this is you need to take the WB out of AWB and set it to something, anything. Set it to either a Custom WB or to one of the "built-in" WB settings.

Good to know! But I will add this, I've lots of panos, including with p&s's, never had this happen with photomerge, that I've noticed. Cheers

pathfinder

The beauty of shooting all your pano frames in RAW, in addition to manual mode with the same aperture, shutter speed, and focus, you can synchronize the RAW processing so that all the frames get exactly the same processing AND COLOR BALANCE when they pop out into Photoshop as processed jpgs.

So when shooting RAW frames, you CAN shoot in AWB, because the color balance will not be finalized until the files are marched through the RAW processor. I know that Scott knows this, but some of our readers might not fully appreciate this point otherwise.