Big Center Filter on a Small Budget?

[Ari]

Hi,
While I wait for the arrival of a Schneider 72mm XL, I thought I'd find out if anyone here has alternatives (read: less expensive) to Schneider CFs.
The Schneider CF for the 72 is at about $550 (ouch); has anyone tried other brands/makers of ND center filters with success?

I ask in idleness, as the question may be moot: I'll use the lens without a CF and see if I really need one.
If I end up needing one, it won't matter, because I won't be able to afford it.

Yes, I know, it's late.

[Mark Stahlke]

You could buy some cheap UV filters and a can of flat black spray paint. Just a squirt of paint in the center of the filter...

You're right, it's late.:D

[John Schneider]

Surplus Shed used to sell large (maybe 8" dia) center filters for the 6" Metrogon as used in aerial cameras. They were either red (looked like #25) or yellow (#12) with a vacuum deposited inconel (most likely) graduated center spot. The spot was quite dense and the graduation out from the dark spot was rather abrupt and not always uniform around the filter, but it would be a cheap thing to try.

[Bob Salomon]

Heliopan CF works and is less and is also more color neutral than the one for the 72.

[Ari]

You could buy some cheap UV filters and a can of flat black spray paint. Just a squirt of paint in the center of the filter...

You're right, it's late.:D

Mark, that's too roots, even for me!
But I like where you're going with it... :)

And Bob, thanks, Adorama lists them at a little less than the Schneiders, but still too much for me.

[Steve Hamley]

Look for a used one, Schneider or Heliopan. They do come up periodically. Of course, this doesn't help if you need one right now. BTW, Igor has several used ones listed.

http://www.igorcamera.com/large_format_lenses.htm

Cheers, Steve

[Ari]

Thanks, Steve; better already at $345, though I don't need one right away.
I thought I'd try a few tests before saving up for a CF if one was needed.

[Steve Hamley]

I'd think if you're using it on 4x5 you won't need it except for extreme movements. 5x7 is probably a different story, where you might be near the edge of the IC.

Cheers, Steve

[E. von Hoegh]

Try gently smoking a UV filter over a candle. You'll be surprised how uniform a spot you can make, but I have no clue what the optical properties will be.

[Ari]

Try gently smoking a UV filter over a candle. You'll be surprised how uniform a spot you can make, but I have no clue what the optical properties will be.

Wow, you guys are more DIY than I thought, and not always the finesse kind of DIY either. :)

[johnielvis]

hay....maybe shoot some technical fine grained pan type film at something grey...focused at infinity...on film much larger than the coverage---so you see the circle darken....then develop it--this will give the general density variation you need...then copy this in the appropriate filter size (image circle enlarged/reduced to the filter size you need) on thick based fine grained film...then cut the film and insert it in the filter in place of the glass...PERFECT, right? that's the ticket....you can make varying compenstating neutral densities like this too...hay hay

[Eric Woodbury]

I waited and eventually found a used one. If you are using the 72 on 4x5, you may not have much of a problem. I use it on 5x7 and there is some fall off, but in some pix it doesn't matter. I've always wondered why these filters cost so much and why someone doesn't make a gel version. So the question might be, how do you make a gel with an ink jet printer? Might be worth a try. Even if it gets scratched. Make a bunch all at once and use as needed.

[Bob Salomon]

hay....maybe shoot some technical fine grained pan type film at something grey...focused at infinity...on film much larger than the coverage---so you see the circle darken....then develop it--this will give the general density variation you need...then copy this in the appropriate filter size (image circle enlarged/reduced to the filter size you need) on thick based fine grained film...then cut the film and insert it in the filter in place of the glass...PERFECT, right? that's the ticket....you can make varying compenstating neutral densities like this too...hay hay

Thick base fine grain film is not the best thing to put in the optical path if you do not want to effect resolution.

[Bob Salomon]

I waited and eventually found a used one. If you are using the 72 on 4x5, you may not have much of a problem. I use it on 5x7 and there is some fall off, but in some pix it doesn't matter. I've always wondered why these filters cost so much and why someone doesn't make a gel version. So the question might be, how do you make a gel with an ink jet printer? Might be worth a try. Even if it gets scratched. Make a bunch all at once and use as needed.

They cost so much because they are very difficult to manufacture and the market for them is very small. In the past they had to throw away almost as many imperfect ones as they could make perfect ones.

Rodenstock has now come up with a new way to make a center filter using an optically clear blank that is concave and a neutral grey blank that is convex. When the two are sandwiched together they make an absolutely neutral color center filter as unlike other CF that work by absorbtion and reflection these new MC center filters only absorb light. Full details are available here:

http://www.rodenstock-photo.com/mediabase/original/Filter_brochure_Center_2010_CD_Engl_10184.pdf

[aduncanson]

For a lark, it might be easier to DIY a Goerz Hypergon style fan.

[John Schneider]

Rodenstock has now come up with a new way to make a center filter using an optically clear blank that is concave and a neutral grey blank that is convex. When the two are sandwiched together they make an absolutely neutral color center filter as unlike other CF that work by absorption and reflection these new MC center filters only absorb light.

This sounds like the same principle used by Rodenstock to make the CF for their ancient Pantagonal (that one used green rather than gray glass to better correct for the films of the era).

http://webcache.googleusercontent.com/search?q=cache:1hvMtzaxsfUJ:photo.net/large-format-photography-forum/004Mxh+pantagonal+filter+center&cd=4&hl=en&ct=clnk&gl=us&client=firefox-a

[Bob Salomon]

This sounds like the same principle used by Rodenstock to make the CF for their ancient Pantagonal (that one used green rather than gray glass to better correct for the films of the era).

http://webcache.googleusercontent.com/search?q=cache:1hvMtzaxsfUJ:photo.net/large-format-photography-forum/004Mxh+pantagonal+filter+center&cd=4&hl=en&ct=clnk&gl=us&client=firefox-a

I would doubt that there is anyone at Qioptiq who remembers anything about there lenses and accessories from back then. Part of the secret to these new CF are that they are multicoated on the front of the clear glass and the back of the rear glass so the coating eliminates stray light from reaching the image plane.

This new technology is not used on all of their CF. Only on their new 72, 77 and 86mm ones. Basically these were developed for the new 23, 28 and 32mm Rodenstock lenses used primarily for digital and roll film. Those lenses do not cover 45 at all.

[domaz]

I'm surpsied no one mentioned the digital approach. If you are scanning that is basically free. Schneider seems to have made an expensive Photoshop plugin (http://www.digitalcenterfilter.com/) to do it. There is also a free program (http://www.fourmilab.ch/netpbm/pnmctrfilt/) but it's pretty Linux-centric although it would probably work on Cygwin (Linux command shell for Windows) if you are enterprising.

[Sevo]

Schneider seems to have made an expensive Photoshop plugin (http://www.digitalcenterfilter.com/) to do it.

WTF? 149€ per lens for a package merely giving a unscientific wrapping to something very close to something that has been a built-in Photoshop functionality for several major releases?

[Ari]

WTF? 149€ per lens for a package merely giving a unscientific wrapping to something very close to something that has been a built-in Photoshop functionality for several major releases?

That's right! :)

I think domaz has a good point; I'm planning on going filterless for a while, so I'll try to fix anything in PS first.

[Will Frostmill]

Ari,
Isn't the standard Photoshop hack to take a picture of an evenly lit white field, scan it, invert it, and use the light falloff pattern as a mask? In darkroom terms, that would be using the taking lens as the enlarging lens.

Will

[Ari]

Ari,
Isn't the standard Photoshop hack to take a picture of an evenly lit white field, scan it, invert it, and use the light falloff pattern as a mask? In darkroom terms, that would be using the taking lens as the enlarging lens.

Will

That's a good point and a very good idea too, Will.
I tend to prefer somewhat darkened corners, but clients will see things differently, and they are right, too.
Thanks for that.

[Ari]

I was able to download the Schneider CF plug-in for free, since I had the serial number and lens registration number.
At first glance, it is lens-specific; it brightens the corners very subtly, and is a plug-in geared toward the digital back user.
Nonetheless, it seems effective, so it's worth a second look once the lens arrives and I get to try it.

[Ivan J. Eberle]

Cheapest solution might be to use neg film instead of transparency, scan and print digitally. (If you later get a client who needs a shoot done on original transparency film, make them foot the bill for a filter.)

[Will Frostmill]

You are welcome Ari! It's fun to be helpful - happens so rarely :)

[Dave Hally]

Why not make a circular gradient in Photoshop and print it on clear base ( Mylar)? You could play with different densitys and gradients for cheap. What would be the best stock to print on, and would the ink/pigment be neutral enough?
Just a thought.
Dave

[Ari]

Thanks, Dave.
A little similar to what Will was suggesting, but with the addition of a piece of film (Mylar).
I'm starting to think that the light falloff will not be so bad; the PS filter from Schneider is easy to duplicate in PS with careful use of a vignette filter, especially if shooting 4x5 and not 5x7.
I suspect some of the hype might be Schneider trying to justify the sale price of $545, but I'm sure some of it is also warranted.

[Dan Fromm]

Ari, I was sort of with you about not needing a center filter 'cos I wasn't using all that much of the lens' coverage. In my case, 2x3 with 35/4.5 Apo Grandagon on a Century Graphic.

Then I shot a nice dramatic lake -- Clyde Butcher sort of sky -- with trees at the ends of the frame. Dark trees. On E100G. Couldn't get a satisfactory print of the whole tranny, too much difference between center and edge.

By all means use your lens without a CF. For many situations mine isn't really needed. But when it is, it is.

I was patient, eventually found a used Rodenstock center filter for my lens for, IIRC, $225 plus postage. BTW, in spite of what Bob S. posted about the new wonderful Rodenstock center filters, my old wonderful one is also made from two pieces of glass with the same refractive index etc., one with something in it that cuts transmission. This is an old trick.

[Ari]

Thanks, Dann.
You're right, only experience will show when the CF is needed and when it isn't.
More on this later, when the lens is in my hands and out in the wide world.

Thanks to everyone.