Center Filter for 47mm XL

[xiaubauu]

I am new to this lens and would like to know if I need Centre filter for Schneider SA 47mm XL on a 4x5 format? I notice that it has a 4x (2stop) Centre filter so it might have some pretty pronounce vignette. From your learned experience, is it very pronounce? or it helps if I stop down to f22 or less?

sorry for the noob question.

Thanks in Advance.

[xkaes]

See my test result thread. I tested light fall-off for this lens.

[Corran]

It has pronounced fall-off due to optical characteristics of an ultrawide lens. Whether or not you "need" the CF depends on your personal taste/aesthetic. Issues will be most apparent with high-contrast, low dynamic range film like chromes, especially with scans that can't handle deep shadow. I use a CF almost always with my Schneider XL lenses (38mm through 90mm), though occasionally I get away with not doing so on the 58mm (and only on 617 when using the 72 and 90). I use it even for black and white - see my latest images on the medium format thread as an example of the 38mm XL on 6x9, with the 2-stop filter.

If you are shooting black and white or maybe even color negative* film I would try it out first and decide if you want the filter to even the exposure out. You can always burn down the edges but bringing them up is harder if they go to deep shadow.

*In my experience color negative film will be okay in terms of density but color shift may occur due to the fall-off characteristics when pulling up the shadows, so YMMV.

[EdSawyer]

Yes, you pretty much need it, heavy vignetting in the corners on 4x5 without it.

[Jac@stafford.net]

From your learned experience, is it very pronounce? or it helps if I stop down to f22 or less?

In my experience, a center filter will have no significant effect unless it is stopped down to at least f/16, so f/22 is a good start.

[Dan Fromm]

Jac, FWIW, Rodenstock and Schneider both recommend stopping down two stops from wide open. More won't hurt.

[xkaes]

In my experience, a center filter will have no significant effect unless it is stopped down to at least f/16, so f/22 is a good start.

Maybe you mean "no significant effect UNTIL it is stopped down to at least f/16". My test results on the lens -- see my LIGHT FALL-OFF post -- shows a TWO stop fall-off at f5.6, which diminishes to a ONE stop fall-off at f16. In other words, the wider the f-stop, the more important a center filter is.

[Bob Salomon]

Maybe you mean "no significant effect UNTIL it is stopped down to at least f/16". My test results on the lens -- see my LIGHT FALL-OFF post -- shows a TWO stop fall-off at f5.6, which diminishes to a ONE stop fall-off at f16. In other words, the wider the f-stop, the more important a center filter is.

The instructions from Heliopolis, Rodenstock and Schneider for their center filters is that the lens must be stopped down at least two stops from wide open for the center filter to have an effect on the exposure.

[Martin Aislabie]

I have a friend who bought a 47XL and within a few weeks had to do and buy himself the CF for the lens.

You could try without it for fun but the fall is pretty extreme and you'll probably end up buying one.

Martin

[Jac@stafford.net]

Maybe you mean "no significant effect UNTIL it is stopped down to at least f/16". [.../]

I read your post in the voice of a former Oxford England girlfriend. It was not amusing. Thank gosh I have lived now for eighteen years with an entirely literate professional English editor who is Irish. :)
.

[xkaes]

I wasn't trying to be amusing or sarcastic. I was just trying to figure out what you meant. So now I'm totally confused, and others might be too.

[Bob Salomon]

I wasn't trying to be amusing or sarcastic. I was just trying to figure out what you meant. So now I'm totally confused, and others might be too.

No confusion necessary. A center filter simply does not work unless the lens is stopped down at least 2 stops. It is really very simple.

[xkaes]

It might be simple to you, but it is the exact opposite of what I see in my test results. The greatest light fall-off occurs when the aperture is wide open, and it diminishes as the lens is stopped down. Consequently, it would appear to me that the wider the aperture, the more helpful a center filter would be.

[Dan Fromm]

Joe, stopping the lens down reduces mechanical vignetting by reducing the size of the exit pupil. The exit pupil is occluded more by the end of the barrel when the lens is wide open than when it is stopped down.

I just checked this with a Fuji 65/8 SW. With it mechanical vignetting is present but not a real killer. It is a real killer with my 45/9 CZJ Goerz Dagor. That lens' barrel is too narrow and its outer elements are too small for it to do as well as cos^4 except at tiny tiny apertures.

Mechanical vignetting depends on the barrel's dimensions and the exit pupil's location. It is extremely lens-specific, cos^4 is universal.

Center filters are designed to reduce the effects of loss of illumination off-axis at cos^4(the angle off-axis). This falloff is predictable.

Your observations are fine but your interpretation of them isn't.

Edit: I neglected to say clearly that mechanical vignetting is also dependent on the aperture. No one CF will address its effects. Its much better to stop down until mechanical vignetting is under control and use a CF that understands cos^4.

[Armin Seeholzer]

I very seldom use my CF on my 47 XL Schneider!

But its me!

[xkaes]

When are you most likely to use it?

[Thalmees]

Maybe you mean "no significant effect UNTIL it is stopped down to at least f/16". My test results on the lens -- see my LIGHT FALL-OFF post -- shows a TWO stop fall-off at f5.6, which diminishes to a ONE stop fall-off at f16. In other words, the wider the f-stop, the more important a center filter is.

The instructions from Heliopolis, Rodenstock and Schneider for their center filters is that the lens must be stopped down at least two stops from wide open for the center filter to have an effect on the exposure.

Hello Bob,
Manufacturer notes are not meant to be followed literally. Specially if it was abstracted piece of Information.
The lens is an extreme wide angle for 4X5 format.
I do not think it will cover the format properly at f/11( 2 stops from f/5.6).
Lens alone Without center filter:
Coverage at f/5.6 is 98° and 110mm circle, and
at f/22 is 120° with 166mm circle of coverage.
With CF, relative illumination across the frame can be better at any given aperture, but the true coverage is not necessarily the same.
I think the lens should be stopped to f/16 at least, in the first place, then the CF can do the trick.
The corners of the frame is well below 20% relative illumination at f/22, could not imagine what relative illumination is at f/11 in the corners? Correctable?
The statement could be true information in general for any CF, but not necessarily true for any wide angle lens.

[Bob Salomon]

Hello Bob,
Manufacturer notes are not meant to be followed literally. Specially if it was abstracted piece of Information.
The lens is an extreme wide angle for 4X5 format.
I do not think it will cover the format properly at f/11( 2 stops from f/5.6).
Lens alone Without center filter:
Coverage at f/5.6 is 98° and 110mm circle, and
at f/22 is 120° with 166mm circle of coverage.
With CF, relative illumination across the frame can be better at any given aperture, but the true coverage is not necessarily the same.
I think the lens should be stopped to f/16 at least, in the first place, then the CF can do the trick.
The corners of the frame is well below 20% relative illumination at f/22, could not imagine what relative illumination is at f/11 in the corners? Correctable?
The statement could be true information in general for any CF, but not necessarily true for any wide angle lens.
Read what I wrote. It had nothing to do with the coverage of the lens. I stated that your lens had to be stopped down at least 2 stops for the filter to have an effect. You should shoot at the diffraction limited stop, if possible. And, you want to avoid stopping down to far to avoid diffraction.

[xkaes]

No confusion necessary. A center filter simply does not work unless the lens is stopped down at least 2 stops. It is really very simple.

From: http://www.galerie-photo.com/center-filters-for-large-format-lenses.html

"I’ve seen comments about center filters’ +1.5 and +2 markings to the effect that these are adjustments to exposure times. Schneider and Rodenstock literature on center filters make it very clear that the markings refer to f/stop adjustments to be made when using a center filter."

So now I'm completely confused. If I'm using my 47mm f5.6 and meter a scene, I have to chose a speed and stop down -- at least f11 (when using a 2 stop CND) for it to have any affect. But then I have to open the diaphragm to f5.6 to compensate for the ND -- so I'm back where I started at f5.6 where the CND has no affect.

The only way out of this is to meter the scene and choose a speed and aperture stopped down at least to f22, so that when I open up two f-stops to adjust for the ND, I end up at f11 -- two stops down from wide open. Correct?

[Bob Salomon]

From: http://www.galerie-photo.com/center-filters-for-large-format-lenses.html

"I’ve seen comments about center filters’ +1.5 and +2 markings to the effect that these are adjustments to exposure times. Schneider and Rodenstock literature on center filters make it very clear that the markings refer to f/stop adjustments to be made when using a center filter."

So now I'm completely confused. If I'm using my 47mm f5.6 and meter a scene, I have to chose a speed and stop down -- at least f11 (when using a 2 stop CND) for it to have any affect. But then I have to open the diaphragm to f5.6 to compensate for the ND -- so I'm back where I started at f5.6 where the CND has no affect.

The only way out of this is to meter the scene and choose a speed and aperture stopped down at least to f22, so that when I open up two f-stops to adjust for the ND, I end up at f11 -- two stops down from wide open. Correct?
Either apply the filter factor before you meter or increase your exposure time. But in either case make sure that you have stopped down at least two stops.

[Jac@stafford.net]

xkaes, another way for 2 stops is to under-rate the film by two stops. For example, ISO 400 set the meter to ISO 100. For ISO 100 set the meter to 25.

Set the lens to f/11 and choose the shutter speed on the meter that matches.

[Dan Fromm]

The only way out of this is to meter the scene and choose a speed and aperture stopped down at least to f22, so that when I open up two f-stops to adjust for the ND, I end up at f11 -- two stops down from wide open. Correct?

Exactly, but your thinking is too convoluted.

The largest aperture at which you can use the CF is f/11. The CF cuts illumination by 2 stops. 2 stops down from f/11 is f/22. So you want to use the shutter speed that gives good exposure at f/22.

I don't have to think hard 'cos I can count on my fingers. I don't have to think hard 'cos I have a Horseman meter.

If you want to play narrow depth of field games like the digital types who shoot fast lenses wide open you shouldn't use y'r CF.

[xkaes]

I get it. It seems the approach I would use -- assuming I actually get a CND filter at some point -- would be to select the f-stop I want to use, that is at least two f-stops down from maximum. Then adjust the ISO with the filter factor for the CND filter, and meter the scene. Then use the shutter speed for that selected f-stop.

[Bob Salomon]

I get it. It seems the approach I would use -- assuming I actually get a CND filter at some point -- would be to select the f-stop I want to use, that is at least two f-stops down from maximum. Then adjust the ISO with the filter factor for the CND filter, and meter the scene. Then use the shutter speed for that selected f-stop.

You really do make things unnecessarily complicated! How do you tie your shoes? Or do you just wear flip flops?

[xkaes]

I'm strictly bare foot.