Can the center filter be replaced by post-processing?

[Bob Salomon]

Then use a less dense ND filter and ditch the polariser. A center filter will accept one filter with a thin ring. Add more and you'll have problems.

Or get a high quality variable ND filter!

[Pere Casals]

Is the fall-off something easy to fix in photoshop (I could not find clear examples on the internet)?

With photoshop: https://www.youtube.com/watch?v=G83PU7iDYhA
With lightroom: https://www.youtube.com/watch?v=90IFl69WFVA

Digitally, it's easy to correct fall-off, there are several ways, but the lens correction tool does it pretty well.

In a darkroom it's also easy to correct it in the printing process, we have several techniques for that. First we can use an enlarging lens that has fall-off that will compensate the fall-off in the negative, we also may print a mask in a transparency and we may make a sandwich with the negative and a diffuser sheet, and we can also manipulate the illumination of the enlarger to make it compensate what the negative has, we also may place a mask in the light path instead making the sandwith with the negative.

But, as Bob Salomon noted, the fall-off in the taking may bring on problems because it can exagerate the dynaming range the scene has, making more difficult to capture all scene range with quality.

So in scenes with narrow Dynamic Range we always may make the correction in the post, for scenes with large DR we may have problems, but also all depends of the ammount of fall-off we have depending also on focal and aperture, and the film latitude, with slides we have to be careful with that.



I'd recommend this reading by Ken Rockwell that (IMHO) sports a lot of wisdom in that, it shows when CF it's worth or not, and even how you may take advantage of fall-off as a creative resource:

https://kenrockwell.com/tech/center-filters.htm
https://web.archive.org/web/20180224...er-filters.htm

[rpagliari]

Then use a less dense ND filter and ditch the polariser. A center filter will accept one filter with a thin ring. Add more and you'll have problems.

What kind of problems would I run into?
I typically use the lee system with polariser and one nd filter.

Thank you

[pgk]

FWIW. I have an early Leica 28mm f/2.8 Elmarit-M - the version 1 which had some design input from the Super-Angulon according to some sources. It shows significant vignetting. Sometimes I use in an a Sony A7II and being of a curious nature I try different lens 'pre-sets' during the RAW conversion to see whether any suit it. Surprisingly if I set it as being the Sony 28mm f/2 FE lens, a great deal of the vignetting is dealt with. Which suggests to me that the Sony lens has substantial vignetting which is mostly dealt with in software one way or another.

However, using a centre filter has the advantage, as already stated, of dealing with 'uneven' exposure at the taking stage and as such is technically a 'better' option, depending on what you are going to do in post processing later. In extreme conditions where substantial adjustment is needed to an image in post processing I suppose both tonality and noise might become an issue although I doubt this will happen often.

And also FWIW I did use a Hasselblad XPan 49mm centre filter on a Super-Angulon-M for a while but actually found that some of the 'character' of the lens was lacking in that evening out exposure across the frame did emphasise the lower lens performance (mushier detail) at the edges and corners.

Lastly, I have learnt practically that stacking filters which include a polariser has sometimes produced soft corners so I tend not to do so.

Just my POVs though.

[rpagliari]

I shot this last Saturday with Nikon 75mm f4.5. I cropped a bit off the right side. I did some vignette removal with PS.


Kent in SD

Thanks for sharing this Two. This result is very acceptable to me, in fact, I could not tell the difference.

[Huub]

The main risk you will run when stacking filters is that of vignetting as it will decrease your image circle, next to possible quality loss due to adding extra surfaces that might cause reflection and other forms of image degradation. I am not sure how that would work out with the Lee filters you are using.

I agree with others that you could try to leave out the ND filter and replace it with the center filter. Otherwise you could try for yourself and see what happens before buying the center filter. I am using both a 75mm and a 58mm without the center filter and compensate in the darkroom. For the 75 mm I overexpose about half a stop and for the 58mm I use a whole stop to make sure i keep enough shadow detail in the corners. But then: i do only b&w and when using slides it will be a complete different story.

And one more thing: stopping down a 75mm to f32 brings you well into defraction range. Defraction can be noticed when the physical size of the diafragma becomes less then about 5mm, which translates to f16 for a 75mm lens. Whether this loss of sharpness is acceptable is something you have to decide for yourself.

[Dan Fromm]

What kind of problems would I run into?
I typically use the lee system with polariser and one nd filter.

Thank you

With an ultrawide lens and a center filter?

As has already been said, vignetting.

Folks, the OP has stated very clearly that he wants to take long exposures, in the 4 to 8 minute range.

[JimboWalker]

I have had limited experience with this , but I have investigated this very same issue with my new (old) S-K 65mm f8 Super-Angulon. I do not have center filter. The filters cost more than the lens! Try exposing one stop over and even out the vignetting in PS. My limited testing seems to have real possibilities. You do not want to drastically underexpose the vignetted areas of the image to loose shadow detail. Good luck, Have fun!