Can the center filter be replaced by post-processing?

[rpagliari]

I am in the processing of buying my first 4x5 camera.

I'd like to know how heavy vignetting is with wide angle lenses (Schenider 75mm f5.6 in my case). I can buy the center filter as well but, apart from price, it adds an extra 1.5 stops.

I typically do long exposure and 1.5 extra stops could make the exposure much longer than needed.

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

Thank you,

[Bob Salomon]

No!

[rpagliari]

is it worth it with 75mm and above?

[Dan Fromm]

It may be worse than you think, OP.

Rodenstock and Schneider recommend stopping the lens down 2 stops to get the full compensating effect. This is because of mechanical vignetting, which is reduced by stopping down. Center filters compensate only for optical vignetting. Whether this matters for you depends on the apertures you normally use. What apertures do you normally use?

You say you're going to be exposing for 4 to 8 minutes. Do you work in natural dim light or do you make your own with ND filters?

If you use ND filters, the solution is simple. Less density. And don't forget to put the ND filter in front of the center filter to avoid mechanical vignetting.

If you shoot in dim light, well, you'll have to expose longer. There's no way around it.

Spell out what you're doing. This will make it easier for people to help you.

[Dan Fromm]

is it worth it with 75mm and above?

Many photographers shoot 4x5 with lenses as short as 90 mm without center filters. Few 4x5 photographers who shoot lenses shorter than 90 mm use them without center filters. Read this: http://www.galerie-photo.com/center-...at-lenses.html

Re "75 mm and above," which way is up? <75 or >75?

[rpagliari]

I am planning to use f/32 with ND filter and polariser for an exposure between 4 and 10 minutes.

[Bob Salomon]

I am planning to use f/32 with ND filter and polariser for an exposure between 4 and 10 minutes.

Besides the fall off that a center filter corrects you will also be well into diffraction at f32, and you can’t correct that.

[rdeloe]

Maybe, but it depends on lots of things. Working with RAW files (and even JPEGs) in the digital world, we're often dealing with huge amounts of light falloff due to the lens design. Modern lens designs frequently assume that vignetting will be corrected in camera (and the user will never know), or in software. Case in point is a modern lens like the Fuji XF 10-24 mm f/4R OIS. At the 10mm focal length and at f/4, vignetting reaches as high as -1.93 EV according to Lenstip's testing. People who shoot JPEG think it's a terrific lens because the camera evens things out before writing the JPEG file to the card. RAW developers like the one in Lightroom apply the correction on import so you may not even know it happened if you're unfamiliar with the issue.

Film is not a RAW file, but assuming you have information, you can raise the values. However, if the vignetting from the lens was very heavy it could look nasty. You can see for yourself even if you don't own the lens yet. In your workflow, how many EV can you raise the shadow parts of an image you shot on film and scanned before you're unhappy?

[Two23]

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

[Dan Fromm]

I am planning to use f/32 with ND filter and polariser for an exposure between 4 and 10 minutes.

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.