Stiching Photos In PS CS3 (Exposure Difference)

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).
The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.

I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

A number of possibilities (it’s very hard to guess what might have been happening from that crop):

– lens vignetting (most lenses have minor variations from centre to edge, and sometimes laterally)
– the light was changing between shots
– the camera may be inconsistent (eg slight shutter speed variations)

There may be others, but those are the most likely imo.

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).
The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.

I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

Probably vignetting (dark corners). Running them through a vignetting correction first should improve things.

—
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).
The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.

I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

You don’t say what camera you’re using and strangely enough the EXIF data is cleared.

You say that it was all a single exposure setting. Are you sure? Did the light change between shots?

The ‘upper band’ is a bit darker suggesting that either the light changed or the metering did.

This is not, btw, "stacking" but mosaic/panoramic. Stacking refers to two other processes (one for DOF deepening and one for noise reduction in (mainly) astrophotography).

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Paul Furman wrote:

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).
The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.
I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

Probably vignetting (dark corners). Running them through a vignetting correction first should improve things.

No, it’s not vignetting there, not by a long shot. The bottom row is differently exposed. Why is speculation.

—
John McWilliams

John McWilliams wrote:

Paul Furman wrote:

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).

The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.
I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

Probably vignetting (dark corners). Running them through a vignetting correction first should improve things.

No, it’s not vignetting there, not by a long shot. The bottom row is differently exposed. Why is speculation.

Increased contrast shows that possibility:
http://edgehill.net/1/temp/2mi5i4z.jpg
Overlap could mask out the vignetting on the bottom row.

—
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

"Glen" wrote in message

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).
The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.

I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

Thanks for the replies.

I must admit, the first thing that came to my mind too was that it could have been due to lens light fall off at the edges, but I had the benefit of seeing the whole picture/the individual photos and as John mentioned, this was not the cause.

Well, I am still not sure why it is doing it, however I think that I was maybe using the wrong tool for the job. If I use ‘Automate > Photomerge’, instead of ‘Scripts > Load > Files Into Stack (Automatically Align Source Images)’, there’s no problem. For some strange reason, I thought that loading them into a stack was a better technique than using Photomerge, but it turns out this is not the case.

Here’s a comparison (Photomerge is the bottom one):
http://i39.tinypic.com/2a0gbw7.jpg

Paul Furman wrote:

John McWilliams wrote:

Paul Furman wrote:

Glen wrote:

Anyone come across this before?

In PS CS3, if you stitch multiple exposures by going to Scripts > Load Files Into Stack (Automatically Align Source Images), there are slight exposure differences between the images (I.E. you can see the square edges of the individual photos where there are exposure differences).

The shots were all taken using manual exposure so the aperture, shutter speed, ISO, etc were identical, and also identical RAW settings were used for all shots in ACR before stacking them.
I can’t think why there should be any exposure differences between shots when it stitches them together.

http://i42.tinypic.com/2mi5i4z.jpg

Probably vignetting (dark corners). Running them through a vignetting correction first should improve things.

No, it’s not vignetting there, not by a long shot. The bottom row is differently exposed. Why is speculation.

Increased contrast shows that possibility:
http://edgehill.net/1/temp/2mi5i4z.jpg
Overlap could mask out the vignetting on the bottom row.

I phrased that poorly. While vignetting may well be there, the problem is overshadowed (pun intended) by the absolute differences in exposure.

—
John McWilliams