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11-05-2009, 01:59 AM   #1
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exposure differance

Hi,
I am using a K20D to shoot images used in virtual tours. I use it in manual mode with the view finder covered and am also using expose lock from one image to the next. The problem is when I stitch the images i am getting an exposure differance between some of the images. Any ideas on how to stop this happening?

Thanks

11-05-2009, 02:12 AM   #2
Damn Brit
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It depends at which point you take the meter reading. When I take panoramas, I pan the camera round and take meter readings from various points then use the average.
Are these virtual tours for real estate or something? Inside a house is going to be hard, light changes drastically.
11-05-2009, 02:19 AM   #3
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yes, basically they are used for real estate and therefore inside. I take a series of six shots and usually take an average also. I always try to show the room off nice a brightly, therefore over expose windows, which I fix with onther series of shots under exposing the room.
11-05-2009, 03:02 AM   #4
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Check if you don't have "Auto EV compensation" on. This will override your set up if the camera "thinks" you're about to screw up.

11-05-2009, 04:35 AM   #5
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Auto EV Comp. is off. Any other ideas?
11-05-2009, 06:54 AM   #6
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If you aren't allowing anything to change, IE you are in manual exposure mode with auto RV compensation turned off, then the most likely culprit is a lens that isn't stopping down smartly, or else a defective shutter that isn't maintaining exposure repeatability.

Try this: in manual mode with the lens wide open, take a half dozen or more pictures of the same scene (put the camera on a tripod and don't move it) and see if they are all identically exposed.
Then stop the lens down to a middling small aperture, say f/8 ot f/11 and repeat the test (do adjust the shutter speed to give correct exposure).
See if this series is all identically exposed.
This should pin down your culprit.
If both series show identical exposure, then it is something you are doing on site, not the equipment.

Something that makes me wonder, if you are in manual mode, then why are you using exposure lock? The whole idea of manual mode is to lock in a discrete exposure. Perhaps this is your problem and pressing the exposure lock button is causing things to go sideways.
Just a thought.
You shouldn't be using the exposure lock in this type of shooting.
11-05-2009, 07:18 AM   #7
graphicgr8s
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How long are you taking to get all the shots? It needs to be done fast. And on a tripod. I usually set manual exposure, with no compensation at all on the center of my pano. Than start shooting from right to left. And yeah I do that stupid 1 finger shot at beginning and 2 finger shot at the end. When you stitch in photoshop usually it will automatically adjust the pictures for you though.
11-05-2009, 09:04 AM   #8
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Can you post some examples with EXIF intact?

11-05-2009, 12:56 PM   #9
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This image is one of the worst.

Last edited by Damn Brit; 11-05-2009 at 01:23 PM. Reason: Added IMGWIDE tags
11-05-2009, 01:25 PM   #10
Damn Brit
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You might be better off with a P&S with a pano feature.

BTW, if you download large images in future, please use IMGWIDE tags, I've edited your post above.
11-05-2009, 01:33 PM   #11
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Thanks for posting that, but meant, post the individual images, so we can see what actual exposures were used - to make sure they really were all shot with the same ISO, f-stop, and aperture.

As it is, what strikes me about the pano is that exposure looks consistent enough, but WB doesn't. You need to control that, too. If you let it sit on AWB, then it might (and did) choose a different white balance for different parts of the scene based on what it perceives to be the color of the light, and the light *is* in fact different in the different partsof that scene. You meed to choose a specific WB (one of the presets, or use manual) and stick with it - or else shoot RAW and apply one WB to all of the images in PP.
11-05-2009, 01:53 PM   #12
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Marc's suggestion is good.
All parameters need to be the same, not just Av, Tv and ISO. WB needs to be off AWB, of if not, shoot in RAW and standardise each parameter.
11-05-2009, 02:04 PM   #13
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Thank for your help guys. I am shooting a property today. I will use raw and see if I can fix it from there. But i have checked everything that has been suggested all all looks ok.
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