Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: druryphoto on April 07, 2011, 06:56:37 am
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Hi
I had some trouble with white shading when using my 24mm digitar lens and Sinar 75lv. I shot what I thought was an acceptable white shading and then made my exposure. Upon downloading the images I have a magenta hue on the left of the image and a green hue on the right. It would appear as though the shadfing file has not succesfully reppaired the image. The exposure times were quite long aprox 8 seconds for the image and considerably longer with for the shading file. Could the exposure time be the problem.I was thinking that it might not be a white shading issue at all?
I was also using the camera in master mode instead of x-contact. I am wondering if this could have been the issue? There is absolutely no documentation of what the master mode is so I am not sure if I should be using it or not but it is the only way to increase the exposure time.
Any advice about this would be apreciated.
thanks
Carl
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Digitar 24 and Sinarback 75LV. And the camera was??? What was the set up in the back? Was the camera/back connected to computer or did you shoot on to the CF card?
The white shading file of Sinarback 75LV is in the back - when shooting on the CF card you can make a white (grey) balance manually. Only if working with computer, you can make additionaly white shading for the lens or for the scene.
Master modus - you trigger from camera and the camera triggers the back.
Slave modus - you trigger the back (need a sinarback trigger) or you trigger from computer when conected and back triggers the camera.
When using MF cameras like Mamiya AFD..., Hasselblad H1/2, Contax etc. and you are conected to the software (Captureshop) in most cases / configurations / you can choose on the fly to trigger the camera or to trigger from computer.
I don´t know if this will help you but I hope you´ll find a way to take pictures without magenta and green hue.
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Hi
thanks for the reply. I'm using it on the cambo wds and shooting to the internal memory. I'm creating a white shading file with the sinar white filter on the front of the lens. To be honest, on reflection, I don't think it is the shading file not working. I think it may have more to do with the long exposure. I am wondering if anyone else has issues with the back when doing longer exposures? This didn't happen with all my exposures either.
I suppose that it could also have been a flare issue..... even though it would seem a strange flare that produces magenta and green.
Also as far as I'm aware you always make a white shading file for each new scene. It shouldn't make a difference if you are tethered or not. I am still using Exposure to download the files and then using the shading mode to correct the images.
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What you have said with your shading mode via non-tethering (ie eXp) process is exactly what I have been doing. I have NOT done any long exposure shots with the 75LV yet. But I have seen long exposure tested by my supplier and no issues as per your description. So perhaps what you have concluded ie flare may be the cause - can't say but perhaps do some few new short exposure shots and see what they turn out.
Cannot wait for Sinar to incorporate the non-tethering shading mode into CaptureShop - heard great things about what to expect or at least the wish list. :)