Filters in Front of a Long Lens

[Steve G]

In my experience, schneider filters seem to be best. Less colour shift in nd grads.

If going for tiffen, water white glass is best.

[Pawel Achtel]

Clearly, this could not have been settled without a proper test.

The Setup:

• Van Diemen Leica Apo Telyt-R 580mm at f/4.0 (the biggest caliber I could find)
• Schneider 6.6" x 6.6" 85+PL Combo filter
• Schneider 6.6" x 6.6" Coral Grad #1 Filter
• EOS 50D with PL mount

Now, you guys have to guess the results

[Sam Taylor]

Pawel what were you testing? They are both schneider filters. Maybe you were testing with filter and without? Thanks,

[Pawel Achtel]

Yes, tested with and without filters in front of a long lens with a large aperture.

[David Rasberry]

Thanks for posting the article Pawel. Useful info indeed.

[Sam Taylor]

Please tell us Pawel!

I expect that there will be a loss in image quality, but that "noticeable" difference in the final shots/footage will depend on the size you are viewing at, and also the nature of the footage. With stills viewed on a large screen yes it will be quite obvious, but for a lot of moving footage viewed on the tv or web much less obvious. Eg if you shot a clip of a car speeding towards you in daylight with the ND on, versus not then the overall better image resulting from using the ND would outweigh the loss of sharpness, which would be less of a problem due to the moving subject. However if you are filming a stationary figure for a long distant shot, then yes.

[Pawel Achtel]

Scientifically speaking the result of putting a (high quality) filter in front of a long (580mm), fast (f/4.0) high quality lens lens WFO is equivalent to smearing a layer of Vaseline over the front element, basically.

In the next few days I'm going to do some tests at f/5.6 and f/8 but, I think, I will get the idea of using filters in front of long lenses out of my head.

[David Rasberry]

Is this perhaps why some big long lenses have filter slots at the rear? (Other than front element size being too big)
How does a rear mounted filter behave by comparison?

[Pawel Achtel]

Is this perhaps why some big long lenses have filter slots at the rear? (Other than front element size being to big)

Right! And it has one. That's right: ONE!

[Pawel Achtel]

How does a rear mounted filter behave by comparison?

You can't remove the rear filter. It is part of the optical design. The lens won't focus properly without it. You can insert different filters, including clear, which is present in both crops.