Center filter question

[narikin]

Anyone else noticed the conundrum between the manufacturer advising us to use latest generation digital lenses near wider open, f5.6 or 8, rather than f.11/16, and the increased fall off you get at those apertures? You can have sharper images with more fall off, or less sharp ones with less fall off. Take your pick.

Regardless of that - does anyone know of less strong center filters for moderate wide angles? I know the heavy wides have their dedicated filters, but for something like a 50mm on MF digital, it appears there is not a filter, unless someone can suggest a 3rd party one? Thanks.

(I am familiar with using LCCs but sometimes am bothered by those strong adjustments, and their effects on shadow areas in corners)

 

[gazwas]

You mean Rodenstock recommends f5.5-f8, however Schneider still recommmend f8-f11 for their digital lenses last time I checked.

I think you will find the SK60XL has a dedicated centre filter and a super lens too.

 

[narikin]

yes the newest Roddys seem to say wide to 2 stops down for best resolution, so depending on the lens, e.g. the 40mm or 50mm HR Alpagons are both f4, so thats f 4, f5.6 to f8 max. The 50mm teeters on needing a center filter at f5.6.

 

[narikin]

BTW - can someone explain all the Schneider center filters naming?

I can't make sense of weakest to strongest, in respect to the numbering IIa IIb IIc IIIc IVd, etc.

 

[Shashin]

Since it is an angular problem, you could just try a center filter and see if that evens things out for you. Take one of the less dense ones.

 

[jotloob]

yes the newest Roddys seem to say wide to 2 stops down for best resolution, so depending on the lens, e.g. the 40mm or 50mm HR Alpagons are both f4, so thats f 4, f5.6 to f8 max. The 50mm teeters on needing a center filter at f5.6.

I got my HR DIGARON-W 4/40 back from RODENSTOCK where it was adapted for SB 17 .
I did a test series with all apertures and the CFV-50 (zero sharpening in PHOCUS) and found the best results (sweet point) are received at f=8.5
Rodenstock only offers CFs for the HR23 and HR28 .
I do not use a CF with my HR28 + CFV-50 as the sensor is only 37x49 and I can not see any vignetting nor darker corners .

 

[Paul2660]

In the latest Digitar's from Schneider, there is a dedicated physical CF for the 28mm, 35mm, 43mm and 60mm. I am not sure on the actual numbers for them as I ordered them all through Rod Klukas, U.S. Arca rep.

With Rodenstock, and the HR-W they have a dedicated physical CF for the 23, 28 (same physical filter) and the 32mm. 40mm and up there is no physical CF listed.

I have used the Schneider 35mm 43mm and 60mm on a IQ160 and the CF effects each lens a bit differently.

I feel the SK 35mm needs it on all the time as it will show pretty bad corner fall off even on center without it. If you shift at all, it's a must have to help even out the frame (and LCC).

The 43mm will do OK on center without the CF, but once you start to shift it shows pretty bad fall off and CF helps quite a bit especially if you are shifting past 10mm.

The 60mm doesn't need the CF on center and it really only helps on shifts past 15mm. The 60mm SK is the only lens I have that can shift to 20mm on the IQ160 without total loss of saturation and detail smearing.

The Rodenstock 28mm is improved on center with the center filter in most lighting situations. The CF is 2.5 stops so there is quite a bit of light fall off even in this lens. You can't shift the 28mm much more than 5mm before the disk hits the frame and ruins the image. However of all of the wides I have listed the 28 Rodenstock does the best without a physical CF.

As has already been mentioned, the each of these companies has set a ideal range of aperture for their lenses. I have found the Schneiders are best in the F8 +1 to F16 range especially when shifted. The Rodenstock 28mm is very good at F5.6 and is excellent at F8 to F11. Much past it you start to see diffraction problems.

It's still impressive just how much image Capture One 7.1x can recover with the Schneiders with a good LCC.

Paul Caldwell

 

[narikin]

Thanks Paul. Interesting information to have.

I've been a little surprised by the 70mm circle on the new HR Roddy's, they are great and super sharp within that circle, but you really can't get much above 15mm of shift at infinity.
The 90mm and up are a big improvement.

 

[Paul2660]

The 23 and 28 HR are a bit older in design with the 70mm image circle. On a 40 x 54 sensor, the 28mm hits a disc or something inside the lens at around 7mm. It creates a total black vignette and will ruin the top and bottom corners. This is on a shift. I believe you can get just a bit more in rise and fall due to the layout of the 40 x 54 sensor. You can see excellent examples of this in Guy's review of the 28's on this forum under the product reviews where he does a detailed comparison of the Schneider 28 and Rodenstock 28.

It's sad that the Rodenstock has this issue since as the actual glass imo on a 60mp sensor will easily go to 12mm maybe 14mm without either sharpness falloff or detail smearing, but the hard black corners will really cause problems. Guy's review shows this issue. The Schneider will get out that far, but has other issues in color and detail fall off with larger shifting.

The 28mm Rodenstock on a 1:1 cropped or 1:3 cropped sensor would go further on shifts before the hard edge comes into play.

Paul Caldwell