Wild manual exposures with M8 and CV 12mm

borrel

borrel

Børre Ludvigsen
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In taking a series of MANUAL exposures with a CV 12/5.6 on my M8 at 125/8, the exposures come out wildly uneven with the sensor apparently trying to compensate in wholly dark areas. The series was taken on a special panorama head and stitched successfully to a QuickTime panorama, but the transitions between the different exposures rendered out of focus in blending. How do I make this camera make fixed, manual exposures like my 5D using a similar focal length? The results are here: http://abdallah.hiof.no/exposure_problem/ ANY suggestion and solution will be appreciated.

- Børre Ludvigsen

PS. This post had a somewhat embarrassing but helpful solution: http://abdallah.hiof.no/exposure_problem/jpg2/
 
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The M8 has true manual settings. I'm not sure what you are asking. Just move the shutter speed dial off of "A" and you can make any shutter speed you like. There is also an exposure compensation - EV - under the Set Button menu.
 
is the stitching program trying to adjust the exposures? I always do them manually in PS, so I am not familiar with software of that type.

Have you disabled the AWB? Are you shooting raw?
 
The exposures all look the same--you must remember that the EV values of the sky and trees in shadow are not the same. Take a look at the sky througout all the exposures--all images including the sky show it consistently, with the same depth and exposure. There is nothing wrong with your camera, you just are assuming all areas of the photo to be exposed at the same level when they inherently have varying levels of reflected light.
 
I have no experience with the M8, but I've done a lot of pano shots with DSLRs, so perhaps this will be relevant.
Wide angle is not the best way to go with pano stitching. Between the lens distortions (even minimal), perspective distortion, vignetting and exposure variations across the wide fov, they're just hard to stitch together. Also, a big part of the incentive for pano shots (for me) is the extra large file I get. That means lots of smaller fov shots stitched together.
I've had good sucess using 28mm on my 1.6x crop and 50mm on full frame. I guess I'd select 35mm on a 1.3x crop if I had a chance.

I'm not sure what to suggest as a cause for the out of focus blending...except perhaps the software trying to account for the distortion from the ultra-wide perspective.
 
Have a closer look at images 2 and 10. That is the same yellow bush in the bottom of 2 and the top of 10. Click the images to see larger versions and verify the difference. - Børre
 
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Is it me? Looks fine to me. The sky is always similar, so is the ground. Sunny bits ofcourse lighter than shades.
Nice stitching by the way!
 
dazedgonebye said:
Wide angle is not the best way to go with pano stitching.
Click to expand...

The top two rows and several of the other panoramas on this page: http://abdallah.hiof.no/kongeveien/ were made with the CV 12/5.6 on an R-D1. The remainder with a 5D and a 17-40 fixed at 17mm. We also do spherical panoramas with a 10mm fisheye.

The problem is that the exposures come out of the camera uneven - when the shutter speed is set to manual.

- Børre
 
borrel said:
The top two rows and several of the other panoramas on this page: http://abdallah.hiof.no/kongeveien/ were made with the CV 12/5.6 on an R-D1. The remainder with a 5D and a 17-40 fixed at 17mm. We also do spherical panoramas with a 10mm fisheye.

The problem is that the exposures come out of the camera uneven - when the shutter speed is set to manual.

- Børre
Click to expand...

I'm unable to download the necessary software to display those here at my workplace.
My experience has been long the lines of rectilinear images of perhas 120 deg fov. I can certainly see where wide angle fovs would be helpful for what you're doing.
 
borrel said:
The problem is that the exposures come out of the camera uneven - when the shutter speed is set to manual.

- Børre
Click to expand...

What you are saying is that the camera is recording the exposures at differing levels, even though the camera is set with the same exposure values, on manual exposure settings.

If you are shooting RAW, perhaps the differences are arising in the RAW conversion?

Unrelated perhaps, but I also have great difficulty metering correctly with a 16mm fisheye lens on my dSLR.
 
TTL metering for manual or AE exposure with any wide-angle is very difficult because of the possibility of a large piece of relative light sky fooling the meter.
That's why I sold the Bessa L years ago and kept the 15mm.
Returning to the stated problem: the yellow bush example. Isn't it just a different representation, is the raw image really as different as pic 2 and 10?
All the sky bits look similar. All the ground bits look similar too.
 
EMBARRASSING! ChrisN is right. Camera RAW is the culprit. It's autoexposure feature tries to give all the dng images an even 18% exposure. I'll post the results in a little while.
 
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Thanks again Chris. You might want to see how this panorama appears with the correct exposures: http://abdallah.hiof.no/exposure_problem/jpg2/

As a small compensation for your services in leu of fees, the only way of getting satisfactory exposures with really wide lenses like the 16mm you mention is with a hand held spotmeter. My preference is the Pentax Digital supplemented with a Sekonic L-398.

The rest can be made up for in RAW conversion. ;)

- Børre
 
borrel said:
Thanks again Chris. You might want to see how this panorama appears with the correct exposures: http://abdallah.hiof.no/exposure_problem/jpg2/

As a small compensation for your services in leu of fees, the only way of getting satisfactory exposures with really wide lenses like the 16mm you mention is with a hand held spotmeter. My preference is the Pentax Digital supplemented with a Sekonic L-398.

The rest can be made up for in RAW conversion. ;)

- Børre
Click to expand...

The final version is brilliant! Fantastic! I got dizzy with the sky spinning!

And, thank you for the suggestion about metering! A good excuse to drag out my Pentax Spotmeter V, which I love for its precision.
 
Which 360 precision pano head did you use?

Which 360 precision pano head did you use?

I have the early 360 precision pano head that is designed to be used with a canon 1Ds2 and a 15mm fisheye lens. Which pano head did you use with the M8?

Thank you and best wishes
 
RichEdg said:
Which pano head did you use with the M8?
Click to expand...

I have two heads, one for a 5D with 17-40mm fixed at 17mm, and one with two fixing brackets, one each for an R-D1 and the M8, both using the CV 12/5.6. These two brackets arms were made to measure by 360 Precision on the basis of drawings and measurements sent them by me, so they now have templates for both cameras. Both work very well using either AutoPano or PTMac. The only problem is that because of the very short lens, the fixing screw for the camera is hidden behind the vertical rotator and has to be tightened with an ordinary key or some other dull instrument. If you are interested, I can post some pictures of the setup. Most of the panoramas in the top 3 rows here: http://abdallah.hiof.no/kongeveien/ are taken with the R-D1 and CV 12/5.6.

- Børre
 
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