ND filters and 35mm adapter

T

trez

Well-known member
I read here (post #13):
http://www.cinematography.com/forum2004/index.php?showtopic=33417
that it's not good to use camera-provided ND filters when shooting with 35mm adapters. Instead, the filter should come first - before the adapter (on a mattebox or screwed onto the 35mm lens). Is it true? I've been thinking about it but can't think of any reason...
One thing I like about shooting with an adapter is that I can set the depth of field by choosing 35mm lens aperture and then adjust the exposure in a convenient way by either setting the camera aperture or applying one of the ND filters it offers. If what I read was true, then things are getting much more complex...
 
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I get his point that on some adapters you don't want to stop down the 35mm lens more than f 4, but I can't figure out why it would matter where the ND filter is. Whatever you have to do to allow you to open up the 35mm lens that much would seem to work as well as any other solution, at least in regard to that one point.

Duncan
 
This has been brought up many times here before.
Most external ND glass filters are of higher quality than internal nd filters and that seems to be the only difference.

edit: the old argument was, some people were saying to expose your gg like your film plane, and if you overexpose it by using internal ND's instead of external ND's it would have negative effects on your image. It's pretty much been debunked.
 
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Essami said:
If you use too much ND on the camera and have camera aperture around f8-16 the DOF of the camera lens will be extremely deep. As you are focusing on the ground glass of the adapter this creates a problem and can sometimes bring out artifacts.
Click to expand...

The question is whether it's ok to use in-camera ND filters with DOF adapter. So it has nothing to do with the camera lens aperture. Actually - applying ND filters allow you to open the camera iris, so what you wrote does not explain too much.

It will look like this in the worst case scenario:
http://www.dvxuser.com/V6/showpost.php?p=1187928&postcount=14
Click to expand...

I think this is what it looks like when you stop down the 35mm lens too much. I can stop down my DVX100B iris to f16 when shooting with an adapter and it does not result in any visible grain as long as the 35mm lens aperture is <= f2.8.
(of course, I try to keep my camera iris between f4.0 - f8.0 whenever possible, as this is the sweet spot of the lens - so I'd rather put the ND filter instead of stopping the camera lens further)
 
Matty_g said:
This has been brought up many times here before.
Most external ND glass filters are of higher quality than internal nd filters and that seems to be the only difference.
Click to expand...

OK. If this is the reason then I'm with you. However, the same applies to shooting without the adapter.

edit: the old argument was, some people were saying to expose your gg like your film plane, and if you overexpose it by using internal ND's instead of external ND's it would have negative effects on your image. It's pretty much been debunked.
Click to expand...

This one is funny. It's like pushing you ground glass a couple of f-stops, LOL.
 
Matty_g said:
edit: the old argument was, some people were saying to expose your gg like your film plane, and if you overexpose it by using internal ND's instead of external ND's it would have negative effects on your image. It's pretty much been debunked.
Click to expand...

Its not that you overexpose, its that the DOF is too deep and you get those artifacts.
 
trez said:
The question is whether it's ok to use in-camera ND filters with DOF adapter. So it has nothing to do with the camera lens aperture. Actually - applying ND filters allow you to open the camera iris, so what you wrote does not explain too much.
Click to expand...

Its what Ive found out via experience and testing. Also Steve Cahill wrote about this on his blog and found out it to be the case. Its mostly too look after in very bright conditions, for example on a clear winter day with white snow and bright skys. Which is what you see on the picture I posted. I normally use my Sony EX1 ND at 1 and if I need more I put filters in front of the 35mm lenses. Never had any problems after I started doing this. But as I said Ive only seen the artifacts during the winter time with snow and bright skys.

Discussed here in more detail: http://www.dvinfo.net/conf/let-us-discuss-letus/116104-letus-extreme-5.html

But as someone said the sweet spot of the camera aperture is around 4-6 so its good to keep it there in any case :)
 
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