Filters in Front of a Long Lens

[John Burnley]

I've film tested a 400mm f5.6 Nikkor with and without a Nikon made filter and found no measurable difference in resolution using Air Force charts (as used by "Modern Photography" magazine for its lens tests) and focusing with extreme magnification to get repeatable results at a level of care next to impossible in real world shooting. The only filter I tested was a UV. And there certainly could have been a slight contrast reduction but I was not testing for that.

I briefly had a Nikkor 400/3.5 with a front UV that was bonded in place and that lens was as sharp as other f3.5's w/o front filters.

Also in the past I owned a Century Tele Athenar 650mm f6.3 (later models were f6.8) and found no sharpness difference using a Hoya UV compared to the unfiltered lens, testing with the above charts. But when I tried a (non Nikon) yellow filter (for B&W use) the image went to "mush" so much so that the image was unfocusable. It was a very sensitive lens to filter issues. Current (sharper) Canons and Nikkors would likely be more so.

These were tests of the optics alone, so I used electronic flash as my light source in a dark room (or in the case of the 650mm outside at night). That eliminated mirror or shutter bounce issues in the results.

But the issue HERE for use with Red and Scarlet is not really UV filters but ND's (and others) and I have no experience with them in terms of image degradation at extreme tele magnifications yet.

[Steve Gibby]

I don't use UV filters on my lenses when I shoot with Red - or my DSLRs either. ND filters are the only kind I usually use with RED, except for an occasional polarizer.

I've been using long lenses on my Red cameras quite a bit for the 2.5 years I've owned them. My long lenses are a Nikon 50-300 f4.5 AIS, Red 300 f2.8, Nikon 400 f3.5 AIS, Canon FD 150-600 f5.6L with Century PL mount conversion, and Canon 800 FD f5.6L with Century PL mount conversion. I filter the Nikon 50-300 on the front, the Red 300 and Nikon 400 via drop-in filter trays, and the Canon 150-600 and Canon 800 via end of PL mount screw-on filters.

I've had no problems whatsoever with image degradation from using ND filters as described.

[John Burnley]

I don't use UV filters on my lenses when I shoot with Red - or my DSLRs either. ND filters are the only kind I usually use with RED, except for an occasional polarizer.

I've been using long lenses on my Red cameras quite a bit for the 2.5 years I've owned them. My long lenses are a Nikon 50-300 f4.5 AIS, Red 300 f2.8, Nikon 400 f3.5 AIS, Canon FD 150-600 f5.6L with Century PL mount conversion, and Canon 800 FD f5.6L with Century PL mount conversion. I filter the Nikon 50-300 on the front, the Red 300 and Nikon 400 via drop-in filter trays, and the Canon 150-600 and Canon 800 via end of PL mount screw-on filters.

I've had no problems whatsoever with image degradation from using ND filters as described.

Thanks for posting this, Steve. That is really good to know that quality ND's do not create optical issues for these extreme lenses when used as you indicate.

[Shawn R]

Thanks Steve for the info.

[Pawel Achtel]

I did some more testing on shorter focal length: Leica Apo Telyt 400mm f/4.0. The degradation due to front mounted filter (in this case 6.6"x6.6" Schneider Enhancing Filter) is much smaller and tollerable. 1:1 crops attached. There is slight loss of contrast, but the front filter is usable.

In regard to using filters in front of the much larger Leica Apo Telyt R 580mm f/4.0, I confirm again that the effect is like smearing Vaseline on the front element...

I have contacted several people at Schneider-Optics in respect to their (somewhat misleading) white papers claiming suitability (high flatness and accuracy) of their filters to be used in front of long lenses with wide apertures, but deaf silence, head in the sand reaction...it seams.

It makes me cranky when companies publish "white papers" for their marketing reasons, which are essentially false.

Oh, well, now I have to manufacture my own Series 6 drop in filters...

[Yusuf Thakur]

Though we have only used UV filters on all our lenses 120-300, 50-500,200-400 All Sigma Lenses with RED ONE and Epic,
I have never felt that the UV filters affected Quality.

Rechecked with and without UV filters after reading this and shot multiple charts, did not find any loss in Quality using only
UV front threaded filters.

All the filters are also made by Sigma.

Yusuf Thakur
VFX,Dubai
www.vfxme.com