Software rather than center filter for correcting illumination falloff?

[Dan Fromm]

Greg, the link is in the list.

But since you haven't looked there, here it is: http://www.galerie-photo.com/center-...at-lenses.html

[Corran]

These are post capture, though. If your film's range doesn't capture good tonal definition throughout the picture, then post work won't replace the filter. With bw (and enough exposure), you should be fine. It might be more of a problem with color transparencies.

This!

OK, now we seem to have all players present

Who has the very rare and expensive Center Filters?

What lens do you use on it on?

38mm XL
Schneider 2a CF
On 6x9 - only with chromes
On 6x12 - always

58mm XL
Schneider 3b CF
On 6x9 - never
On 4x5 - always with chromes, sometimes with negatives if I think it needs it

Schneider 72mm XL
Schneider 4b CF
On 6x17 - always with chromes, sometimes with negatives
On 4x5 - sometimes with chromes, probably only if extensive movements are employed

Nikkor 90mm f/8
Schneider 3b CF
On 6x17 - only with chromes
On 4x5 - never

Schneider 90mm XL
Schneider 4b CF
On 6x17 - only on chromes
On 4x5 - probably never unless extreme movements employed on chromes

So in conclusion, mostly only on color positive material and sometimes with negative film with extreme wide angle lenses on certain formats. Almost never on b&w in general.

[Drew Wiley]

No need for Nikon to make their own. For example, the Schneider 82mm CF works perfectly on the Nikkor 90SW. I assume that Fuji super-wides are very similar too. Neither makes XXL wides, so that's a non-issue. You can't correct the corner falloff if it's so extreme or contrasty that not enough visual information is even left there. That's entirely possible with color chrome film, but can even happen with black and white if you drop clear down onto the toe of the film. And with even color neg film, it's possible, even probable, to have a color shift along with extreme density shift, and that kind of thing would be harder to correct. Like I already posted over on APUG, why futz around with a program when it only takes 30 seconds to screw on a center filter? My garsh, they're still being made and sold for a reason. I found a CF to be almost mandatory when doing architectural shooting. Those guys want their own work highlighted, not your creative cutting of corners, if you'll excuse a pun. Even and correctly exposed sheets are also a lot easier to print. But for my personal work, I almost never use true wide angle lenses anyway, so the CF along with the SW sits in its box most of the time.

[Two23]

.... why futz around with a program when it only takes 30 seconds to screw on a center filter?

Well, 30s and $300.


Kent in SD

[Corran]

Used to be, you could find used 3b (IIIb) filters here and elsewhere for $100-150.

Not anymore I guess.

Renewed interest in LF bringing prices back up?

The best deals are lenses + filter together. Newbies don't realize that's even a thing, ask these questions after getting their first wide-angle, and then are looking for just the CF...

[C. D. Keth]

I think the best way to do this, without having the correct filters, would be to photograph a bald blue sky or a blank wall slightly out of focus. Aim for boring middle grey in the center of the negative and adjust the scan to reflect that value precisely, because middle grey is neutral in a dodge/burn mask layer. The lighter edges of the scanned negative will dodge the edges of your image proportionally to how much they’re darkened.


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[Drew Wiley]

Kent, $300 and likely even more than that might seem like a lot for a filter, but people spend far more on high-end wide lenses, and you're only as good as your weakest link. And let's face it, the cost of color sheet film adds up mighty fast these days. 8x10 is running around $30 a shot now with processing, and the new Kodak E100 4x5 is about half that much. Therefore can one afford NOT to use a center filter? With black and white work, it's more a personal esthetic decision. I often get turned off by over-the-top blackened corners, but it depends on the specific image. I'm addicted to long lenses anyway. But like I already hinted, back when I did architectural shots for architects, historical restorations, etc. it wasn't an optional issue, especially if a chrome was intended for publishing. Lack of a center filter would lose you the job.
And CK, the old trick was to use an enlarger lens with an equivalent amount of illumination falloff to balance out the falloff of the wide angle lens. But there are also reasons for not doing it that way. A digitally printed custom mask would not only have to be tailored for each lens, but at multiple f-stops for each, and be so large that it can be shifted all around to mimic the effect of camera movements. Not an ideal approach. I have used a CF filter on an enlarger lens itself for special effect, but it had to be well stopped down to work right. Whatever. The best investment of all is a leftover scrap of matboard black on one side and white on the other for basic edge and corner burning. Maybe for digital printers there some new kind of Cardboard Scrap App that does the same thing.

[C. D. Keth]

And CK, the old trick was to use an enlarger lens with an equivalent amount of illumination falloff to balance out the falloff of the wide angle lens. But there are also reasons for not doing it that way. A digitally printed custom mask would not only have to be tailored for each lens, but at multiple f-stops for each, and be so large that it can be shifted all around to mimic the effect of camera movements. Not an ideal approach.

You don’t have to be that perfect about it. Generally, the scenes where somebody bothers to use a wide enough lens to need a center filter will have a lot going on to hide small inconsistencies in the size or hardness of that falloff. This method will get you 90% of the way there 90% of the time and costs a sheet of film and a bit of time.



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[Drew Wiley]

Well, if you specialized in Cibachromes like I did, you'd discover that skating right at the edge of the ice rink when exposing the chrome might very well crash you into the wall when printing it. Do you have any idea how much sheer candlepower it took to take a damn 4X5 Velveeta transparency with an attached .90 density contrast mask and make a 30x40 inch print? And if you sent a publisher a chrome like that they would take one look and say, No way. Of course, nowadays people say they can do "anything" with a scan. But down in those deep underexposed shadows, you hit hardpan oversized-grain blue crossover. But breaking the rules was sometimes fun too. Crossover had its creative advantages sometimes, but rarely for commercial work. Jes sayin'. There's a reason I rarely shot Velvia. And there's also a reason I still keep a set of center filters on hand, just in case.

[C. D. Keth]

Well, if you specialized in Cibachromes like I did...

Does anyone know if there is a software application (since I scan my 4x5 negs) that would allow correction of wide angle falloff instead of using a ND Center filter?

Were we not still talking about negatives that are being scanned for printing á la the OP?


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