Best center filter for Rodenstock Grandagon 90mm f4.5

[Paul Greeves]

Hi,

I have a Rodenstock Grandagon 90mm f4.5 lens. I am using it to shoot 5x7 and 6x17. I tried it without a center filter but there was just too much light fall off. While this isn't an issue with b/w, it is with colour negative, as altering the density in post production also changes the colour. I bought a Schneider 82mm IV filter with 1.5 stop correction but there is still a degree of light fall off, to about a stop. The test images were taken with an aperture of f16.

My question is: is this to be expected or would I do better to keep the filter and swap the lens for the Schneider 90mm f5.6, that the filter was designed for. Both lenses have the same angle of view (105 degrees) and 235mm of coverage.

Cheers

Paul

[Bob Salomon]

Why not sell the filter and buy the correct Rodenstock one?

[hiend61]

I have a 90/4,5 Grandagon in the Sinar version (Sinaron W 90/4,5) and the Rodenstock center filter 82mm 4x. Despite the fact it´s marked 4x (2 stops). I tried the density with an spot meter and it´s really 3x (1,5 stops). I have experienced this with the rest of my Rodenstock Centerfilters (58, 67 and 105 mm) except the one for Apo Grandagon 35/45/55 that is a real 5x factor (2,5 stops). I feel comfortable with this and I find the correction level reasonable. I like a small ammount of vigneting in wide angle potography. When I push my Grandagon 75/4,5 to the shift limit, I use the 2,5 stops filter for Apo Grandagon (it is 67mm size), and get a full correction, but I don´t need to do it frecuently. If you like full correction, try to find a Heliopan 82mm W.w center filter ND 0,90. This filter corrects 3 full stops. It´s no longer made, but at this moment you have one at the famous auction site.

[Drew Wiley]

The Schneider at factor 1.5 should be reasonable. Remember, these CF's are engineered for use ideally at f/22. Try it at that aperture and see if it helps before you go shopping for something stronger.

[Paul Greeves]

Thanks. I will check out that auction site.

My guess is that 3 stops may be just too much. I think 2 stops would be better. At the moment, I am also thinking that it may be a better idea to match the center filter that I have to the lens that it was designed for. I am in discussion with another LF user to trade my Rodenstock f4.5 for his Schneider f5.6 and see if that is a better match up.

[Drew Wiley]

I've used it with Schneider (for which is was originally designed), but it also works utterly perfectly from f/16 down with my 90/4.5 Nikkor SW, which is a superior
lens in my opinion to the Super Angulon. And I have done very thorough testing with film and densitometer to confirm this. Totally even. Plus these particular lenses are a bit of a bargain at the moment, it seems, at least compared to what they were new.

[Jac@stafford.net]

[...] I bought a Schneider 82mm IV filter with 1.5 stop correction but there is still a degree of light fall off, to about a stop. The test images were taken with an aperture of f16.

Rodenstock's center filter for 90mm is also 1.5 stops. F/16 is correct for this filter. I don't know if swapping would help.

[Drew Wiley]

I think the official Rodenstock filter is just a rebranded Schneider anyway. To my understanding, they never made their own C.F.'s. Bob S. would know for certain.

[Paul Greeves]

It may just be that these center filters are designed for use with 5x4 for these lenses. As I am shooting 5x7 and 6x17, I am using the edges of the image circle, where the addition of a center filter may have less of an impact. My thinking with matching the filter and lens is that, although the two lenses have the same image circle, the construction of each lens may be very different.

[Drew Wiley]

Yes, you are getting further out from the typical 4x5 image circle, so that might explain your problem. But do try it at f/22 and see if it helps. I would think that
the 4.5 versions of all the major mfg 90's are very similar optically; so merely switching brands might not help at all.

[Bob Salomon]

I think the official Rodenstock filter is just a rebranded Schneider anyway. To my understanding, they never made their own C.F.'s. Bob S. would know for certain.

They absolutely made their own.

[Bob Salomon]

It may just be that these center filters are designed for use with 5x4 for these lenses. As I am shooting 5x7 and 6x17, I am using the edges of the image circle, where the addition of a center filter may have less of an impact. My thinking with matching the filter and lens is that, although the two lenses have the same image circle, the construction of each lens may be very different.

No center filter will completely correct the fall off. Their will always be some. But to use the center filter properly you must stop the lens down at least 1 ½ stops from wide open. Otherwise the lens will not be correctable by the center filter. Also, non wide angle lenses, like Sironars, Symmars, Nikons, etc also have some fall off.

[Jac@stafford.net]

He stopped down to F/16, which is what Rodenstock recommends.