Silvery Shine Schneider Center Filter III

[Daniel Unkefer]

https://live.staticflickr.com/65535/52291794777_d088c7d9f8_b.jpg (https://flic.kr/p/2nER7Lz)SONY DSC (https://flic.kr/p/2nER7Lz) by Nokton48 (https://www.flickr.com/photos/18134483@N04/), on Flickr


I received this Center Filter III today, and immediately I noticed it has a "silvery shine" when viewed from the front, at an angle, although it seems OK looking through the camera. My inclination is to return it, none of my other Center Filters behave this way. Anybody here know what's going on with this? Delamination or something else?

In this digishot I put it next to my Center Filter IV, which of course does not have the metallic shine. Thanks!

-Dan

[xkaes]

These CND filters are two element filters, so I suppose separation is possible.

I have several CND filters (Schneider, Heliopan and Zeiss Jena) and I can see the effect when some of the filters are viewed at certain angles in certain light.

I can't say that "it" has ever caused a problem in my results.

I suspect it is some sort of reflection of the balsam, but in my case it's so far off to the side I can't image it causing a problem.

Since you have one with and without, a simple test should be easy to do.

[Daniel Unkefer]

XKaes,

Thanks, Yep testing will prove the pudding. Wondering about light from the front "glaring out" a quick look through my shorty Norma with 75mm f5.6 Auto Iris Norma lens (looks great through the camera!) has been begging for a Center Filter. Not a bad deal at $358 from Japan but not if it causes backscatter in the results. Maybe Bob S can explain why this one is so different from my others? BTW I prefer all my stuff to be about the same vintage

Also I thought this filter IV would fit my 121mm F8 Norma Auto Iris lens. But the 121mm is smaller than the filter. So on we go. Also the 121mm is in a Copal Special Shutter. The Center Filter IV fits beautifully my 90mm f5.6 Norma Auto Iris barrel no shutter Super Angulon.

[Mark Sawyer]

I suspect an unusual AR coating, but yes, Bob S. might now better.

[Bob Salomon]

XKaes,

Thanks, Yep testing will prove the pudding. Wondering about light from the front "glaring out" a quick look through my shorty Norma with 75mm f5.6 Auto Iris Norma lens (looks great through the camera!) has been begging for a Center Filter. Not a bad deal at $358 from Japan but not if it causes backscatter in the results. Maybe Bob S can explain why this one is so different from my others? BTW I prefer all my stuff to be about the same vintage

Also I thought this filter III would fit my 121mm F8 Norma Auto Iris lens. But the 121mm is bigger than the filter. So on we go. Also the 121mm is in a Copal Special Shutter. The Center Filter IV fits beautifully my 90mm f5.6 Norma Auto Iris barrel no shutter Super Angulon.

Sorry, never saw this.

[xkaes]

Sorry, never saw this.

I've seen it before, but never paid any attention to it, because it only appears briefly at certain angles under certain light.

I will say that I've seen it in some EBAY auction pictures to some degree or another. Again, I just thought it a passing reflection at an odd angle.

I'll do a little more studying of mine and see if I can create a situation that intensifies the effect.

[lassethomas]

I have one behaving like this. Never had any real world problems with it.

[Dugan]

That looks a lot like the silvery shine on the yellow center filters for the 6" Metrogon.

[Daniel Unkefer]

OK Thanks Everybody! I'll shoot some tests as soon as I have time. Also this CFIII will fit the 65mm f5.6 if I ever get one. Not too likely though cause I have three 65mm F8's

Another Center Filter Question:
I did not realize there are TWO versions of the Center Filter IV. One is 82mm, for the 120 f8 and 90mm f5.6. The other is 77mm, for the 121mm. Therefore, I ordered a 82-77 step down ring, to use the 120mm F8 CFIV on my 121mm. Has anybody here ever done this combo? Another thing to test, better for me, than having to buy yet another center filter. I imagine it will work but we will see

[John Layton]

The variable density of a center filter, from center to edge, would need to be formulated on the basis of the specific fall-off characteristics of a given focal length...so be careful about using a single center filter for two different focal length lenses.

[Daniel Unkefer]

The variable density of a center filter, from center to edge, would need to be formulated on the basis of the specific fall-off characteristics of a given focal length...so be careful about using a single center filter for two different focal length lenses.

Thanks for that, John! I will certainly consider that.

Just to reiterate, the goal here, is to utilize the more modern 82mm Center Filter IV (for the 120mm F8 SA), on the older 77mm 121mm F8 Norma Super Angulon. Will 1mm in lens focal length be a deal breaker? Also there is the thickness of the 82 to 77 step ring which could be a factor. BTW the 121mm F8 covers 18x24cm, but it's really pushing it for 8x10, you can start to see the corners. Right now I am preferring to shoot 18x24cm, I like the way it looks contacted on 8x10 paper, you get a nice black border just the right dimensions in the print.

Not trying to be obsessive, just the chances of finding a 77mm CFIV are slim

[John Layton]

Daniel thanks for clarifying...I'd thought you were wanting to use a single center-filter for a 90 plus a 120mm lens.

But your question regarding the 120 and 121mm lenses feels beyond my purview...as on one hand the theoretical falloff of these two lenses (which share the same basic design) should be about the same...and yet the filter diameters are so different.

I guess my next question would be...what about the actual diameters of the front and rear elements?
Are they equal or at least close?

Then again...is there something about the more "modern" 120 which makes its center to edge dispersion characteristics different from that of the 121? But as these are both non-retrofocus lenses, how could this be?

Of course, there is always the potential issue of optical vignetting in cases of using step-down rings in general...but as for questions of potential differences of theoretical light falloff between otherwise similar focal length lenses of similar design but possibly different element diameters...somebody with more "optical chops" than myself needs to chime in here!

[Daniel Unkefer]

As Stanley Kubrick used to say, "Let's give it a go!" Well as soon as the adapter ring arrives.

[xkaes]

It's great if you can find and afford a CND filter that was designed specifically for your particular lens(es), but there are lots of lenses that can benefit from CND filters -- but do not have CND filters designed for them.

That does not mean you can't use CND filters. It simply means that you need to run some tests to determine if a particular CND filter works for your particular lens.

[maltfalc]

if the filters are vacuum metalized then oxidized to darken the back and prevent reflections off of the lens, a bit of metallic shine on the front wouldn't be unexpected, especially on stronger filters which would have a thicker metallic coating.