The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Centerfilter for Schneider 35mm XL Apo-Digitar

timwier

Member
I just purchased an Schneider 5,6/35 XL Apo-Digital for my Cambo RS1000. Trying to find out if I need the centerfilter when shooting with a digital back (P45)?

I have done some reading about the centerfilter. Some say it is needed. Some say, no need.

Anyone have any experience with this lens and centerfilter?
 

Don Libby

Well-known member
Tim - I have a Schneider 35mm as well and initially shot it without the filter however I bought the filter and haven't removed it in over 18 months. I feel it's well worth the expense.

Don
 

goesbang

Member
Tim - I have a Schneider 35mm as well and initially shot it without the filter however I bought the filter and haven't removed it in over 18 months. I feel it's well worth the expense.

Don
I have the exact opposite experience. I bought the lens with a centre filter and religiously used it for a while.
Then, it occurred to me that LCC in C1 does exactly what the centre filter does, without adding anything in the light path that might degrade image quality and giving me back the stop-and-a half of light it cost me.
I haven't used it since. I have stopped using centre filters with all my tech-cam lenses now.
Cheers,
 

f8orbust

Active member
I try to do as much as possible in camera to get the most optimal exposure possible, and as such I find center filters very useful (on a P45+ size sensor). Remember LCC in C1 is a fine tool, but it isn't a magic bullet; it's simply pushing the edges to match the center. If the edges are a bit noisy anyway (dependent on your original exposure), pushing them another couple of stops isn't the best thing to do. Just my 2c.
 

thomas

New member
I use a CF with large movements for the same reason: avoiding noise at the edges.
It certainly also depends on the sensor... for the P45 I feel 2 stops exposure compensation based on software correction is too much.
Alternatively you can shoot multiple exposures... i.e. one shot exposed for the center of the image circle and another exposed for the edges of the image circle. But post work can be complicated then.
 

Don Libby

Well-known member
You'll still need to shoot a LCC (at least I do) with a CF. I enjoy using the CF with the 35mm for the image it gives me rather than what I got without it. Better image from the start and less problems in post.

Don
 

thomas

New member
You'll still need to shoot a LCC (at least I do) with a CF. I enjoy using the CF with the 35mm for the image it gives me rather than what I got without it. Better image from the start and less problems in post.

Don
I agree. The CF doesn't completely level out the light falloff but it's much easier to fix in post.
 

goesbang

Member
You'll still need to shoot a LCC (at least I do) with a CF. I enjoy using the CF with the 35mm for the image it gives me rather than what I got without it. Better image from the start and less problems in post.

Don
Don, what are the problems you are having in post when you don't use the centre filter? I'm not trying to be cute, I'm genuinely interested.
Cheers,
 

Don Libby

Well-known member
Don, what are the problems you are having in post when you don't use the centre filter? I'm not trying to be cute, I'm genuinely interested.
Cheers,
Siebel, good question and I understand you're not being cute.

Using a centerfilter on my 35mm gives me better color and less caste however the operative word is "less" as you still need to shoot a LCC for post.

I could achieve the same finished image without the centerfilter knowing I'd still have to shoot an LCC and the post processing would be slightly more involved than if I use the centerfilter, shoot the LCC and have less processing involved in getting to the same end. For me using a centerfilter gives me a better image file and at the same time easier to fix in post.

Don
 

goesbang

Member
My understanding of lenscast is that it is primarily a function of the angle at which light strikes the sensor. The more obtuse the angle, the more severe the cast. (This is a generalization. You will in fact notice bands of colour shift as you move towards the outer edge of the image circle. It is not a continuous shift).
Assuming this to be correct, then a centre filter should have no effect whatsoever on lenscast. It is designed to reduce illumination falloff.
The LCC function in C1 combines 2 algorithms - one to correct lenscast, neutralizing the colour shift, and the other to correct illumination falloff. There are sliders to control how completely you want to do this.
My own experience with shooting a LCC frame through the diffuser after each series of shots at a given shift would suggest that both colour cast and falloff are fully corrected even when using no centre filter. (Within a range of tolerance. When you start pushing local contrast as I do in most of my work, you will start to notice some small amounts of uncorrected cast).
The only circumstance I can see where using a centrefilter might help is if the level of falloff from centre to edge is so extreme that it is beyond the adjustment range of the software. The performance of this lens is not that bad, even at f8-f11 where I do most of my work.
As the process of using the LCC software is the same whether you use the centrefilter or not, I'm a little confused about your approach, Don. Am I missing something?
Perhaps Doug and Yair might like to share some wisdom?
 

ggriswold

New member
Not using a center filter with my 35mm, but like Terry that's with a P40+. With the 24mm it's really necessary. If you are in a situation where you need all the dynamic range a MF back can give you across the entire sensor then I would think a CF is a good idea. When you "invoke" the LCC correction with the 35mm on a P40+ you lose about a stop (maybe 1.5?) of DR because the levels on the edges need to be higher. The amount of lens cast (not exposure) does not seem to depend on the use of a center filter.
In a nutshell, I have been using the 35mm and not had a situation where I needed a center filter, but I am sure it is out there waiting for me....
This topic was kicked around a few months ago and at least one poster thought that they had some image degradation with a center filter... I haven't noticed that with my 24mm XL... it was still so sharp it made my teeth chatter. If Don Libby thinks it's a good idea to use one it is probably worth re-examining... even with a 35mm. Really comes down to how much you can bring up your edges without getting noise problems.
Betcha Doug can nail down all these mysteries in a single post.
 
Last edited:

thomas

New member
Am I missing something?
yes, noise.
A software based push of exposure (at the edges in the case of LCC based light falloff correction) results in an effective increase of ISO. So shooting at ISO50 with a lens that shows a light falloff of 2 stops at the edges results in an image with ISO50 in the center and ISO200 at the edges (simplified speaking).
The use of a glass filter does reduce the amount of correction needed in post. Therefore the edges are cleaner (with regard to noise).

a centre filter should have no effect whatsoever on lenscast.
just a side note: a CF may introduce additional color cast. The sensor cast (i.e. the color cast we normally call "lens cast") goes from cyan to magenta whereas a CF in fact may introduce lens cast ... and this one goes from blue to yellow. Former versions of Capture One couldn't correct this color cast flawlessly all the time but since version 4.8 (IIRC) the correction of both sensor and "lens" cast is corrected perfectly.
 

jotloob

Subscriber Member
Has anyone ever tried the SCHNEIDER DIGITAL CF ? ? ?
They are obviously created by NURIZON DIGITAL as CF plugins for PSCS2 and newer .
http://www.digitalcenterfilter.com

The description is in english and german language .
You will also find information on the SCHNEIDER home page .

I have not used any of them so far , but would like to hear if anyone has experience .

I also believe , if you do not use a full "frame sensor back" you will not get very much vignetting anyway and the rest can easily be corrected in PHOCUS .
Sorry , I don't know of C1 but believe that function is available there too .
 

Guy Mancuso

Administrator, Instructor
Not using a center filter with my 35mm, but like Terry that's with a P40+. With the 24mm it's really necessary. If you are in a situation where you need all the dynamic range a MF back can give you across the entire sensor then I would think a CF is a good idea. When you "invoke" the LCC correction with the 35mm on a P40+ you lose about a stop (maybe 1.5?) of DR because the levels on the edges need to be higher. The amount of lens cast (not exposure) does not seem to depend on the use of a center filter.
In a nutshell, I have been using the 35mm and not had a situation where I needed a center filter, but I am sure it is out there waiting for me....
This topic was kicked around a few months ago and at least one poster thought that they had some image degradation with a center filter... I haven't noticed that with my 24mm XL... it was still so sharp it made my teeth chatter. If Don Libby thinks it's a good idea to use one it is probably worth re-examining... even with a 35mm. Really comes down to how much you can bring up your edges without getting noise problems.
Betcha Doug can nail down all these mysteries in a single post.
George I just shot the Alpa TC with 24mm XL all week with my P40+ and yes you absolutely need the center filter with it. As far as degradation I did not notice anything obvious since the images are very sharp with the filter on and you also need a LCC for sure.
 

goesbang

Member
yes, noise.
A software based push of exposure (at the edges in the case of LCC based light falloff correction) results in an effective increase of ISO. So shooting at ISO50 with a lens that shows a light falloff of 2 stops at the edges results in an image with ISO50 in the center and ISO200 at the edges (simplified speaking).
The use of a glass filter does reduce the amount of correction needed in post. Therefore the edges are cleaner (with regard to noise).

just a side note: a CF may introduce additional color cast. The sensor cast (i.e. the color cast we normally call "lens cast") goes from cyan to magenta whereas a CF in fact may introduce lens cast ... and this one goes from blue to yellow. Former versions of Capture One couldn't correct this color cast flawlessly all the time but since version 4.8 (IIRC) the correction of both sensor and "lens" cast is corrected perfectly.
Hmm. Good point, the theory seems sound. I wonder if the fact that I often only partially correct falloff is hiding the noise artefact you describe. I'll run some tests. Just out of curiosity, what back are you using?
 

thomas

New member
Hmm. Good point, the theory seems sound. I wonder if the fact that I often only partially correct falloff is hiding the noise artefact you describe. I'll run some tests. Just out of curiosity, what back are you using?
it depends on the subject, the amount of movements applied and of course also on the sensor whether or not a CF is useful. Also on the lenses, naturally. Without or just little movements I don't use a CF; with large movements I do.
I use a P45 and of course with this ancient sensor noise is something to care about. However, Chris B. (of whom I think he is very demanding re IQ) also has noise issues even with a P65+ -> http://forum.getdpi.com/forum/showthread.php?t=16966
 

thomas

New member
Has anyone ever tried the SCHNEIDER DIGITAL CF ? ? ?
yes, with my 43XL.
IMO it's a very weak tool. The images are undercorrected, the plugin increases contrast at the edges (and therfore also saturation) and ... actually the most important downside... it works gamma-dependent (i.e. the correction of a file in AdobeRGB with Gamma 2.2 is different to the correction of a file in ProPhotoRGB with Gamma 1.8).
The falloff correction is also only based on lens data. But in pratice different sensors produce different falloff. Therefore the correction based on a white reference shot (as provided in C1, Phocus etc.) is much better.
Finally the plugin is quite slow.
 

ggriswold

New member
For the benefit of folks who may not have all these lenses to see the falloff I have photographed 4 LCC plates (Capture Integration.. $20 perfect size includes nifty wrist strap) for:

45mm Rodenstock. No Center Filter
35mm Schneider APO- Digitar XL No Center Filter
24mm Schneider APO- Digitar XL With Center Filter
24mm Schneider APO-Digitar XL NO Center Filter

Shot at f16 the first two, the 24mm at f11.
Imported into Lightroom, eye dropper white balanced and center levels brought up to 78_78_78 %
Obviously you would want to use Capture One to correct the files, but you can see how much fall off there is with the 24mm without the center filter... I never take mine off for that reason.
I am not the right guy to tell you how much fall off there is in each in terms of f-stops.
 
Last edited:
Top