another prblem with wide angulons.....color shift in the center....

greenspun.com : LUSENET : Large format photography : One Thread

would be nice to share experiences with others about some problem....it seems it appears on all lenses with a wider angle than 100degrees......when you use a center filter: in the middle of the lense there is a color shift in the direction of yellow.....or more accurat: at the edges the color change in direction of blue color. this effect seems to appear through the angle of light entrance through the center filter and later through the multicoating of the lense- and it can be drastic...if you shoot a white or a light grey wall a.e. (which i have to do often....cause i am architecture photographer.....) by schneider-kreuznach they couldnt give me any solution of this problem....they just were sending me a fax where they described accuartely what happens physically and that they dont know any solution about. i realised this effect at first with the 47xl lense on 4x5".....so drastically that my client was complaining about the quality.....cause of the drastic change to blue at the edges. the foto looked nearly as a artifical light - spot in the center.....coloring it yellow. who has made similar experieces...and - better- has anyone found a solution for this effect? greatings from europe... rainer viertlboeck

-- rainer (viert@t-online.de), February 13, 2002

Answers

You really should have a dialogue with Rodenstock, since you are in Germany. They published a fact sheet about this and how they changed their center filter 2 years ago.

You might find it helpful.

-- Bob Salomon (bob@hpmarketingcorp.com), February 13, 2002.


Rainer, So, even if you use the 3c central filter you still see the effect? I have this lens and filter and frankly I don't see the problem that you have observed and described. Bear in mind that I am not an architect photographer and not really obsessed with maximum technical stuff... Or my filter has simply been corrected? Good luck

-- Renee Galang (r.galang@chisholm.vic.edu.au), February 13, 2002.

I have the same experience as Rainer, but the color shift is only evident when shooting white or light gray rocks in bright sunlight. 95% of the time it is not a problem.

-- Jean-Marie Solichon (jardin-exotique@monte-carlo.mc), February 14, 2002.

As a possible alternative, there is a software solution "Aquila" to light falloff, with specific filter for common wideangle lenses: http://www.camdynamics.com/engl/software/aquila02_e.htm I have no experience with this software, just read about it on the web.

Åke

-- Åke Vinberg (ake@vinberg.nu), February 14, 2002.


The complicated explanation involving angle of light and multicoating sounds like BS to me. It's more likely due to the centre filter just not being neutral grey.
Centre filters are quite difficult to make, and they're only made in small batches, so it wouldn't surprise me if the ocassional off-colour one was made and sold.

If you place the filter against a piece of white paper in a good light, can you see any colour shift from edge to centre? If so, you should send the filter back to the manufacturer.

-- Pete Andrews (p.l.andrews@bham.ac.uk), February 14, 2002.



How old is the filter? I bought the IIIc for the 47XL a few days ago and although I don't use colour - I have tried Pete's advice re: holding against a sheet of white paper and the effect is certainly neutral. Lee ND grad filters are the same, but an ancient Cokin certainly shows a colour shift!!!!!!! Maybe the newer versions have been "corrected" or maybe you've got a rogue.

-- paul owen (paulowen_2000@yahoo.com), February 14, 2002.

"I have tried Pete's advice re: holding against a sheet of white paper and the effect is certainly neutral"

First the eye does not react the same as film does. Secondly what is "white paper".

If you want to test how neutral or non neutral a filter is you can use a densitometer. But not visually looking at a "white" sheet of paper.

Lastly no center filter is totally neutral. They all will have some color shift. If you get the Rodenstock paper on Center Filters it goes into the problems and the solutions for center filters in some depth (2 single spaced letter size pages and it includes denstitometric log values as well as compensation differences between different center filters.

The paper can be mailed by us to anyone in the US and by any local Rodenstock distributor in other countries.

-- Bob Salomon (bob@hpmarketingcorp.com), February 14, 2002.


Hoya has an interesting solution in that their CF is two lenses sandwiched together, one clear and one with ND glass, the ND glass lens being convex and the clear glass being concave. Do other manufacturers use this process as well, or do the German manufacturers use surface coating to achieve center ND effect?

Åke

-- Åke Vinberg (ake@vinberg.nu), February 14, 2002.


rodenstock use a similar way to trade their cfs, schneider use the convential way with one glass. the problem with hoya and rodenstock seems to be, that it is not possible to make so strong centerfilters as with the conventional method,- although some effects with mirror effects are much better, cause in this way the cf can be have true mutlicoating. but more than effective 1,5 f-stop differecne doesnt exists- if it darkens more this comes because in the corners the grey glass darkens still 0,2 or 0,3 stops- in the schneider way not- here the glass is absolutely clear at the edge , 1,5 stops are too less for my taste, at least with 35mm rodenstock or 47xl schneider optics......but shure a good solution for 58xl or 55/ 65 mm lenses........anyway i havent tried the rodenstock filters- but i will do so. more than one time i was nerved by reflections from lights in the lense/cf.....

-- rainer (viert@t-online.de), February 14, 2002.

"but more than effective 1,5 f-stop differecne doesnt exists- if it darkens more this comes because in the corners the grey glass darkens still 0,2 or 0,3 stops- in the schneider way not- here the glass is absolutely clear at the edge , 1,5 stops are too less for my taste,"

Then you will be happy to know that we still have in stock the 0.9 density center filter from Heliopan in a 49/67mm size. You can possibly still find these at European dealers as well. But they are no longer made as you lose 3 stops of light + you need to stop down for the center filter to work so photographers preferred the 0.45 or 0.40 center filters which are what the German industry uses now (Rodenstock and Heliopan are now 0.45).

The 0.9 density will vignette with short 110 and 120° coverage lenses, however, as the rims are too thick.

-- Bob Salomon (bob@hpmarketingcorp.com), February 14, 2002.



hi bob, but is the heliopan filter made in the technik with the two glasses , as rodenstock is manufactoring the cfs now? cause this sounds really interesting for the multicoating thez can do now....which surely makes sense with such wide angulons if there is some light falling in the lense.... ...i just bought a schneider 3c centerfilter, it makes 2stop, but although i use it now here in spain...i havent seen the results, but i suppose it will work will, they designed it for the 47xl which has 120" circle as the 35 rodenstock. how much does the heliopan vigneting? cause i love to use my 6x12cm back.....and with the 35mm often its haluzinating wide.

-- rainer (viert@t-online.de), February 14, 2002.

The 0.9 were a sandwich with an air brushed spot. Worked very well.

-- Bob Salomon (bob@hpmarketingcorp.com), February 14, 2002.

you know how many millimieters it is cutting the 6x12 image corners with the 35mm?

-- rainer (viert@t-online.de), February 15, 2002.

Hi Rainer

I have the APO Rod. 55mm with the original CF from Rodenstock and I have a shift to green on white walls. It is so dramatically thad I don`t use him anymore, but I will do a testing again and if it still the same comes out they get it back and I want it replaced by a better one! Till now I heard always about a green shift yellow is a new one not nice eather!

-- Armin Seeholzer (armin.seeholzer@smile.ch), February 20, 2002.


"original CF from Rodenstock"

Original CF that was marketed for a very short time as for the Apo Grandagon? Original CF with 0.4 density? Original CF (current) with 0.45 density?

Is this a new or used filter?

No center filter from any manufacturer is totally neutral in color but the current version of the Rodenstock (which replaced all earlier ones at the 1994 Photokina, including those marked for Apo grandagon only) are closer to being color neutral then any other CF.

Armin, you frequently make statements that makes one think you are refering to a newly purchased, unused, item when it turns out it is used.

Please be specific. What CF do you actually have? If it isn't the current one why didn't you buy the current one?

if it is the current one you should check with Rodenstock in Munich or your local Rodenstock distributor to see if you have a filter that is not normal.

-- Bob Salomon (bob@hpmarketingcorp.com), February 20, 2002.



color shifts,,,, it is wrong that a new center filter will correct these coulor shifts. technicans from schneider AND from rodenstock were telling me that there is physically now way to ellimimate these ugly shifts. the new manufactured rodenstock centers are only better in the aspect of reflections- cause they can have a "real" multicoating, as the rodenstock man said. why they write on the schneider centers too that they are multicoated? i dont know.....maybe they are maybe not....the color shift will be the same.... greatings

-- rainer viertlböck (viertl@t-online.de), February 21, 2002.

Hi Bob

To answer your question the CF was a totaly new one from Ott&Wyss here in Swiss and I have to correct 3 f stops for it . Not a demo just new!!!

Greatings from the mountains.

-- Armin Seeholzer (armin.seeholzer@smile.ch), March 30, 2002.


Armin,

Rodenstock Center Filters have the following exposure corrections.

for the 35mm to 55mm Apo Grandagon and the 200mm Grandagon - +2 stops (factor of 4x) For the Grandagon 65mm to 155mm +1.5 stops (factor of 3x)

These factors are engraved on the rim.

If you are correcting 3 stops that is a factor of 9x. Why do you use so much correction?

or are you including the fact that a center filter does not work until the lens is stopped down by 2 stops from wide open?

Or are you using the long discontinued 9x Heliopan Center Filter rather then a Rodenstock one?

-- Bob Salomon (bob@hpmarketingcorp.com), March 30, 2002.


Hi Bob

Last time I had the filter not at hand so now he is just in front of me and I red you what is stated on it: AR-Centerfilter f-stop +2.5 E67/86 Made in Germany Rodenstock and othside on the box is Cat.No. 1094 2403.145.020 So now you have all the exact dates!

-- Armin Seeholzer (armin.seeholzer@smile.ch), March 31, 2002.


"Cat.No. 1094 2403.145.020 "

Did you buy this as new or as a demo?

The current version is Cat. # Cat.No. 1094 2403.139. Not 145 and the exposure factor is 3x. Not 3 stops.

-- Bob Salomon (bob@hpmarketingcorp.com), March 31, 2002.


Hi Bob

I vergott something to mention on the above. I was talking to a guy from Ott&Wyss and he told me thad Rodenstock not anymore produce the + f1.5 one I liked to get thad one. So I got then the stronger one 3 month ago!But not a demo or a used I just paid for a new one!!! Did thad guy liyng to me?

-- Armin Seeholzer (armin.seeholzer@smile.ch), March 31, 2002.


Armin,

Originally when the Apo Grandagon series was introduced Rodenstock also made a special center filter just for the 67mm Apo grandagon series (one Apo grandagon was originally 55mm in diameter but was quickly changed to 67mm to match the rest).

Rodenstock quickly found that the standard 67mm center filter worked better on the Apo Grandagon series so the one originally released for the Apo Grandagons were recalled by the factory.

You can verify which filter is current by going to the Rodenstock web site which is easily reached from our web site www.hpmarketingcorp.com. Then click on photooptics and then filters.

-- Bob Salomon (bob@hpmarketingcorp.com), March 31, 2002.


Moderation questions? read the FAQ