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Wratten Filters on a Scoopic MS


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#1 Will Montgomery

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Posted 02 October 2006 - 05:30 PM

Should I order Wratten filters from Kodak for the back filter on my Scoopic MS or just go with the screw on type?

I have empty filter holders that can be inserted into the camera, just don't know if quality is an issue with this type, and I have no idea costs for ordering a small Wratten filter from Kodak. I need a #85 for sure and probably a few others for b&w.
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#2 Bernie O'Doherty

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Posted 02 October 2006 - 05:51 PM

:) :) :)

Should I order Wratten filters from Kodak for the back filter on my Scoopic MS or just go with the screw on type?

I have empty filter holders that can be inserted into the camera, just don't know if quality is an issue with this type, and I have no idea costs for ordering a small Wratten filter from Kodak. I need a #85 for sure and probably a few others for b&w.

Hi Will,

Go with the lens front. The filter behind the lens changes the light path and throws the focus off slightly. You could use them, but the flange focal depth would have to be adjusted because of this back focus shift.
I normally glue down the filter holders on the ACLs.....with the owners permission, of course !!

Cheers,

Bernie
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#3 Sir Alvin Ekarma

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Posted 03 October 2006 - 06:51 PM

Go with the lens front. The filter behind the lens changes the light path and throws the focus off slightly. You could use them, but the flange focal depth would have to be adjusted because of this back focus shift.
I normally glue down the filter holders on the ACLs.....with the owners permission, of course !!


Does this info apply also to Bolexes? This is the first time I've heard this...
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#4 Mike Rizos

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Posted 03 October 2006 - 08:40 PM

It would apply to all behind the lens filter systems. This is especially critical with wide angle lenses, as the depth of focus is very narrow, and the focus shift can throw the image off. You can stop down the lens to increase depth of focus, but another problem is introduced: any dirt or scratch on the filter will register on film.

On longer lenses above 75-100mm you can use behind the lens filters without the above problems. Depth of focus is large, and the focus shift not a problem.
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#5 Bernie O'Doherty

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Posted 03 October 2006 - 08:43 PM

Does this info apply also to Bolexes? This is the first time I've heard this...


Yes, it does. When a filter is used up front on a lens, it does not change the back focus. By putting a filter behind the lens, you reach the most critical point at which the light bundles to a point. The thickness of the filter changes the light path and brings the focus slightly further back.

There are three solutions: 1) Don't use behind-the-lens filters. 2) Change the back focal distance of the lens. 3) Change the flange focal depth of the camera.

Cheers,
Bernie
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#6 Sir Alvin Ekarma

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Posted 03 October 2006 - 08:43 PM

Thanx for the info!
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#7 Mike Rizos

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Posted 03 October 2006 - 08:43 PM

Didn't the Scoopic come with three 72mm filters? I've seen sets labeled "For Canon Scoopic only". They were skylight, 80, and 85.

Edited by Mike Rizos, 03 October 2006 - 08:44 PM.

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#8 Will Montgomery

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Posted 04 October 2006 - 02:41 PM

Didn't the Scoopic come with three 72mm filters? I've seen sets labeled "For Canon Scoopic only". They were skylight, 80, and 85.

This one didn't, but I didn't buy it new. Getting front lens filters is easy, I can order from B&H no problem.

Interesting that Canon would make the system like that without some sort of back focus compensation; maybe they just thought it wasn't that critical for news gathering.
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