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Author Topic: Strange panoramic issue  (Read 5221 times)

geotzo

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Strange panoramic issue
« on: July 08, 2009, 03:39:13 am »

The image below is a part of a panoramic stitching I did a few days ago. Trouble is, as you can see, that the images on some areas, are very differently lit comparing to all others. Note, that I have been using same settings (i.e. shutter, aperture, Iso etc), for all shots of the pano!!! I can find no reason of why is this happening, but it looks like some images are beeing proccesed by the camera in a different way. As if it is using some shadow/highlight treat. Shooting RAW on a D70 (which I ve never used before, as I am a Canon user on 35mm work), so I m trying to find out what the heck is going on. Any ideas or help will be highly appreciated like always.
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francois

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Strange panoramic issue
« Reply #1 on: July 08, 2009, 03:48:30 am »

Quote from: geotzo
The image below is a part of a panoramic stitching I did a few days ago. Trouble is, as you can see, that the images on some areas, are very differently lit comparing to all others. Note, that I have been using same settings (i.e. shutter, aperture, Iso etc), for all shots of the pano!!! I can find no reason of why is this happening, but it looks like some images are beeing proccesed by the camera in a different way. As if it is using some shadow/highlight treat. Shooting RAW on a D70 (which I ve never used before, as I am a Canon user on 35mm work), so I m trying to find out what the heck is going on. Any ideas or help will be highly appreciated like always.
Just a few questions:
- Did you shot using the Manual mode or Av/Tv? Sometimes (in Av/Tv) there's a safety shift that can correct exposure parameters.
- Do the individual photos also show the issue?
- What software did you use for stitching?

I can see at least five vertical zones.
« Last Edit: July 08, 2009, 03:52:04 am by francois »
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Francois

BernardLanguillier

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Strange panoramic issue
« Reply #2 on: July 08, 2009, 07:34:20 am »

My bet is on different WB settings, copy the WB value to all the shots in the raw processor and your problem will most probably be solved.

Cheers,
Bernard

francois

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Strange panoramic issue
« Reply #3 on: July 08, 2009, 07:51:03 am »

Quote from: BernardLanguillier
My bet is on different WB settings, copy the WB value to all the shots in the raw processor and your problem will most probably be solved.

Cheers,
Bernard
If the photos were shot with the same exposure then that might be a good explanation. The RAW converter might also be set on auto and apply different settings to each photo...

We need to know more!
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Francois

geotzo

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Strange panoramic issue
« Reply #4 on: July 08, 2009, 08:05:40 am »

Quote from: BernardLanguillier
My bet is on different WB settings, copy the WB value to all the shots in the raw processor and your problem will most probably be solved.

Cheers,
Bernard
Well, the images are all firstly beeing processed as RAW, so I check all the metadata after synchronising in Camera Raw and are all the same in terms of numbers. But the appearence on those lighter images is as you see it. Shutter, aperture and everything else is the same. I use Ptgui for stiching, but that has nothing to do with this thing. I can tell the difference on those images when I open them in any application. I need to mention that this has occured three times in different subjects. It just makes no sense.
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francois

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Strange panoramic issue
« Reply #5 on: July 08, 2009, 08:41:40 am »

Quote from: geotzo
Well, the images are all firstly beeing processed as RAW, so I check all the metadata after synchronising in Camera Raw and are all the same in terms of numbers. But the appearence on those lighter images is as you see it. Shutter, aperture and everything else is the same. I use Ptgui for stiching, but that has nothing to do with this thing. I can tell the difference on those images when I open them in any application. I need to mention that this has occured three times in different subjects. It just makes no sense.
Have you tried to do the stitching via Photoshop, just to see if the same issue is present. I'm not familiar enough with Ptgui to give any adviceā€¦
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Francois

BernardLanguillier

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Strange panoramic issue
« Reply #6 on: July 08, 2009, 10:37:14 am »

Quote from: geotzo
Well, the images are all firstly beeing processed as RAW, so I check all the metadata after synchronising in Camera Raw and are all the same in terms of numbers. But the appearence on those lighter images is as you see it. Shutter, aperture and everything else is the same. I use Ptgui for stiching, but that has nothing to do with this thing. I can tell the difference on those images when I open them in any application. I need to mention that this has occured three times in different subjects. It just makes no sense.

Can you try to re-do the conversions after having adjusted manually the WB to the same given value for each of the images?

If there was really a problem at capture then your only chance is to adjust in raw or ps the luminosity level of the sky so as to reduce the gaps to a level that PTgui will be able to manage. This can be a bit time consuming.

Autopano pro often does a better job than PTgui compensating for differences in luminosity between frames, but PTgui is better at correcting light fall off within each single image... no perfect solution unfortunately.

Cheers,
Bernard

geotzo

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Strange panoramic issue
« Reply #7 on: July 08, 2009, 11:06:40 am »

Quote from: BernardLanguillier
Can you try to re-do the conversions after having adjusted manually the WB to the same given value for each of the images?

If there was really a problem at capture then your only chance is to adjust in raw or ps the luminosity level of the sky so as to reduce the gaps to a level that PTgui will be able to manage. This can be a bit time consuming.

Autopano pro often does a better job than PTgui compensating for differences in luminosity between frames, but PTgui is better at correcting light fall off within each single image... no perfect solution unfortunately.

Cheers,
Bernard
So would you say that there is some weird problem with the sensor or cameras processor? I can really think of nothing else. The problem is present on night shots only.
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BernardLanguillier

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Strange panoramic issue
« Reply #8 on: July 08, 2009, 11:24:44 am »

Quote from: geotzo
So would you say that there is some weird problem with the sensor or cameras processor? I can really think of nothing else. The problem is present on night shots only.

Don't know, have you tried what I suggested?

Cheers,
Bernard

francois

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Strange panoramic issue
« Reply #9 on: July 08, 2009, 11:26:17 am »

Quote from: geotzo
So would you say that there is some weird problem with the sensor or cameras processor? I can really think of nothing else. The problem is present on night shots only.
In ACR, if you kept the WB setting on "As shot" and then sync, ACR will really use "as shot" and you won't end up with the same WB for your photos.
« Last Edit: July 08, 2009, 11:28:59 am by francois »
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Francois

pegelli

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Strange panoramic issue
« Reply #10 on: July 09, 2009, 01:51:04 am »

Could also be a slightly sticky aperture in your lens such that it doesn't consistently fully close to the set value with every shot.

Way to test would be to try and reproduce the effect with the lens wide open or with a different lens.

Just guessing trying to solve the problem. Hope you find it, I know these things can "kill" you until you find the cause.
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pieter, aka pegelli

geotzo

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Strange panoramic issue
« Reply #11 on: July 09, 2009, 07:31:38 am »

Quote from: pegelli
Could also be a slightly sticky aperture in your lens such that it doesn't consistently fully close to the set value with every shot.

Way to test would be to try and reproduce the effect with the lens wide open or with a different lens.

Just guessing trying to solve the problem. Hope you find it, I know these things can "kill" you until you find the cause.
That, I never thought and it could make sense cause the lens is kinda old. I ll try again and I ll come back. Thank you all
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Peter McLennan

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Strange panoramic issue
« Reply #12 on: July 10, 2009, 11:34:46 am »

I recall having similar issues when I tried time lapse with my D70.  Internet research revealed that others had found the same problem and had to abandon use of the D70 due to small variations in frame-to-frame exposure.  Your variations look greater than what I was experiencing, however.
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geotzo

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Strange panoramic issue
« Reply #13 on: July 14, 2009, 02:48:08 am »

Quote from: Peter McLennan
I recall having similar issues when I tried time lapse with my D70.  Internet research revealed that others had found the same problem and had to abandon use of the D70 due to small variations in frame-to-frame exposure.  Your variations look greater than what I was experiencing, however.

Oh, never thought about that. I forgot to mention I used a auto pano head for it. But could its trigger cord affect that somehow? How is this possible? Time, exposure, aperture, ISO are the same... I asked the manufacturer and they said nothing like that has been mentioned to them before.
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OldRoy

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Strange panoramic issue
« Reply #14 on: July 14, 2009, 10:20:51 am »

I have no idea what the exact problem you're experiencing is caused by, however fault-finding in all complex systems basically comes down to the same procedure: change one parameter, repeat the process which exhibited the symptom, see what happens. Then revert to the previous setting, change a different parameter, see what happens.

Make a few test panos without leaving your home. Change one thing at a time, see what the results turn out like. Sooner or later it should become obvious what's going on, if you are systematic. The key to all fault finding (which is how I earned a living for a long time) is reproduceability: if you can produce the fault repeatably more than once, you're well on the way to finding the answer.

FWIW there look to be big exposure variations in the shots you have been assembling. Can't remember whether anyone commented similarly, but make sure that you don't have exposure bracketing on. On the stitching, PTGui can use its own blending code, or Enblend or Smartblend (assuming you have installed them and pointed the application at them). They  all behave slightly differently, but I'd say the variation in your sample shots is bigger than any blending application will accommodate successfully.

Systematic testing is what's required. It's easier to be systematic at home when under no pressure or obligation to get a result. It doesn't matter what the camera's pointing at so long as there are enough features for the stitcher to work with.

Roy
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geotzo

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Strange panoramic issue
« Reply #15 on: July 14, 2009, 10:33:52 am »

Quote from: OldRoy
I have no idea what the exact problem you're experiencing is caused by, however fault-finding in all complex systems basically comes down to the same procedure: change one parameter, repeat the process which exhibited the symptom, see what happens. Then revert to the previous setting, change a different parameter, see what happens.

Make a few test panos without leaving your home. Change one thing at a time, see what the results turn out like. Sooner or later it should become obvious what's going on, if you are systematic. The key to all fault finding (which is how I earned a living for a long time) is reproduceability: if you can produce the fault repeatably more than once, you're well on the way to finding the answer.

FWIW there look to be big exposure variations in the shots you have been assembling. Can't remember whether anyone commented similarly, but make sure that you don't have exposure bracketing on. On the stitching, PTGui can use its own blending code, or Enblend or Smartblend (assuming you have installed them and pointed the application at them). They  all behave slightly differently, but I'd say the variation in your sample shots is bigger than any blending application will accommodate successfully.

Systematic testing is what's required. It's easier to be systematic at home when under no pressure or obligation to get a result. It doesn't matter what the camera's pointing at so long as there are enough features for the stitcher to work with.

Roy
Thanks for that, I ll go through the entire process will see what happens. Thanks to all, I ll come back when I find what is going on
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gardenvalley

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Strange panoramic issue
« Reply #16 on: July 22, 2009, 06:58:52 pm »

Quote from: geotzo
Thanks for that, I ll go through the entire process will see what happens. Thanks to all, I ll come back when I find what is going on

I think Francois came close to analysing this `problem`. It`s a simple case of underexposure. If you take a series of shots for a panoramic with extreme contrast like this, then manual will only work if you check the histogram and make adjustments for each shot by exposing to the right. If you had taken the same entire scene with only one shot the result would have been the same but without the obvious transition from correct exposure to under-exposure . The other clue is there also when you state that it only happens on night shots. This means extreme contrast. I also use a D70 for panoramics and never have any problems. I don`t follow the conventional `wisdom` which advises using manual exposure because I found too many exposure variations due to different parts of the scene having different reflective qualities. The smallest increment you can set is 1/3 of a stop, but the meter in your camera can set stepless speeds such as 1/67 or 1/93. I use aperture priority, check the histogram for each shot and make any adjustments as necessary, ensuring that the histogram goes as far to the right as possible without clippng. For stitching I use Arcsoft Panoramamaker 4. Drop in the RAW images, press the button and it gives perfect results 9 times out of 10. I hope this helps.
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