Digital Centerfilter from Schneider

[tesfoto]

From Cambo Newsletter:


New Super-Digitar 5,6/28 XL

Following the introduction of the Apo-Digitar 43 XL, Schneider continues with a completely new designed 5,6/28 mm lens which will become available within the next months. The Super-Digitar 5,6/28 XL is also very suitable for the latest CCD's with the 40x54mm capture area. This 28 XL offers a 90mm image circle, which represents a 115 degrees viewing angle, with only 0,7 % distortion.  The resolution at f/8 is 80 lp. The complete WideRS Lenspanel will be available as WDS-547. The mechanical construction of the Super-Digitar will not allow to be delivered in a Tilt/Swing panel however.
Both new lenses include a version of the new Digtal Centerfilter.

Digital Centerfilter

Wide-angle lenses are characterised by decreasing light intensity towards the edge with increasing angle of view, which makes the corners appear darker and is unwelcome in many cases. In conventional film photography concentric gradient filters referred to as CENTERFILTERs were developed. These filters have a higher density in the centre of the image and increase transmission towards the edge.
CENTERFILTER for analogue photography have to be mounted on the lens before the film is exposed. They correct the brightness reduction by a fixed value, usually 1.5 or 2 aperture stops. ANALOGUE CENTERFILTERs consist of a glass plate that is coated with a special ND grading in a complex production process and a filter ring that positions the plate at an exactly calculated position in front of the first lens.

Why use a DIGITAL CENTERFILTER?
In contrast to analogue photography, in digital photography each image is stored in a file and can be (post-)processed using suitable software. If the brightness reduction of the lens over the whole image circle is known, it can be corrected -provided the edges of the image were sufficiently exposed- with the aid of special software, the DIGITAL CENTERFILTER. A DIGITAL CENTERFILTER can also be used for correcting the edge brightness reduction in analogue images after they have been digitised for processing.

Advantages of this DIGITAL CENTERFILTER:
- The filter is applied after the image has been taken, so that the full brightness of the lens is retained
- Virtually 100% edge shading correction available, even with offsets (offset can be entered in the software)
- Continuously variable correction of the exposure value - aperture 0.1, 0.5 or 1.5, anything is possible.
- A correction can be discarded and repeated, if necessary
- No additional glass in front of the lens system that may cause reflections and reduce the resolution
- No risk of vignetting of centerfilter holder
In order to enable users to create optimum images, Schneider-Kreuznach and Nurizon Software have developed a DIGITAL CENTERFILTER as a plug-in for Photoshop® (from version CS2).
Schneider Kreuznach - Nurizon DIGITAL CENTERFILTERs are based on the exact specification for the corresponding Schneider Kreuznach lens and therefore guarantee optimum correction of the brightness reduction in wide-angle images.
The software for the Photoshop® plug-in and the lens-specific file for the DIGITAL CENTERFILTER will be included in the price of each Schneider Kreuznach wide-angle lens from May 2010.
Further files for using a DIGITAL CENTERFILTER for other focal lengths are available as options.




It sounds very interesting indeed, but I wonder how they will calculate off center movements.

Checked out Nurizon website (no English Version) and it seems you need to put in the data your self ?

http://www.nurizon-software.com/produkte_AcoSuperGER.html

Have anyone tried the Acolens Nurizon sofware.

The 28mm seems like a very interesting lens.

Cheers

TES

[tho_mas]

It sounds very interesting indeed, but I wonder how they will calculate off center movements.

The falloff is corrected based on measurements of the whole image circle. So you just type in the amount of movements (similar as in Alpa Lens Corrector).

Checked out Nurizon website (no English Version) and it seems you need to put in the data your self ?

if you buy the software you have to create your own profiles unless Nurizon provides them as presets (by now Canon + Nikon lenses only).
You can also rent the target.
But if the "Digital Center Filter" is shipped togehter with the Digitar lenses I am sure they provide lens profiles (anything else wouldn't make sense).
I assume the "Digital Center Filter" is a downgraded version of Acolens "Super Shift" which actually includes the correction of distortion, light falloff, color shift and perspective corrections. And which is quite pricy. In contrast the "Digital Center Filter" obviously only corrects light fall off.

I tried several times to get a trial of Acolens ... but they couldn't manage to send me the software and the target.

[klane]

Is the new 28 a retrofocus? i think it has been stated before but i cant recall...

[tesfoto]

The falloff is corrected based on measurements of the whole image circle. So you just type in the amount of movements (similar as in Alpa Lens Corrector).

Thanks Thomas.

This was what I was afraid off, then you have to keep track of you movement on paper or voice.

I tried to created an LCC archive, to be free of shooting LCC on the spot but just record lens movement. What a disaster I lost my notes on one assignment, on another assignment I could not figure out my own notes. Never again notebooks, now I shoot a plexi for LCC at the end of each shot. I was hoping tha Acolens could work with the LCC file and calculate the movement and then correct the lens falloff.

I can only hope that Schneider will have a normal center filter, or I will not buy the lens.

4-5 years ago I got a testversion of Acolens but I never figured out how to install and get it to work.

[tho_mas]

I can only hope that Schneider will have a normal center filter, or I will not buy the lens.

there's another drawback with "digital centerfilter" resp. LCC based light falloff - if there is a falloff of say 1.5 stop and you push luminance at the edges you end up with 1.5 stop higher ISO at the edges. Depending on the DB that might be okay or might not...
So unless you shoot multiple exposure for center and edges an analogue CF still has it's place.
Supposedly light falloff with the 43XL is less than with the 47XL... but we will see.

[pcox]

Yes, I find myself wishing for a real center filter for me Schneider lenses for this reason. However, I guess there's a problem with these filters and digital backs - they generate reflections between the sensor and the opaque part of the filter, leading to artefacts. Anyone seen this first hand?

Peter

there's another drawback with "digital centerfilter" resp. LCC based light falloff - if there is a falloff of say 1.5 stop and you push luminance at the edges you end up with 1.5 stop higher ISO at the edges. Depending on the DB that might be okay or might not...
So unless you shoot multiple exposure for center and edges an analogue CF still has it's place.
Supposedly light falloff with the 43XL is less than with the 47XL... but we will see.

[tesfoto]

Yes, I find myself wishing for a real center filter for me Schneider lenses for this reason. However, I guess there's a problem with these filters and digital backs - they generate reflections between the sensor and the opaque part of the filter, leading to artefacts. Anyone seen this first hand?

Peter

I use centerfilters on the 24XL, 35XL and 47XL, never seen the artifacts you describe. But I do see your point.

However since I always use the centerfilter I have not tested if there is any quality improvement without.