What do we think? I know many people have given up on the real things, but is that because the digitals are better or are we just lazy and finding shortcuts?
"Digital Center Filter" is a marketing term. It just means the software is brightening up (or "pushing") parts of the image after capture. Like any "push" it increases noise in the shadows. In this regard it matters where you are starting from. If starting with an [email protected]
and a properly exposed image you'll increase the noise from "essentially none" to "very very little". If starting with a [email protected]
and an underexposed image you'll increase noise from "a good bit" to "a ton".
The Schneider/Rodenstock options for this can only be applied to a TIFF or JPG. If you're going to do digital correction it's much better to do this at the raw file stage for both workflow and quality reasons. This is what Capture One's LCC tool is for. It can be applied quickly, in batch, and draws off the quality of the original raw data.
The Schneider and Rodenstock optical center filters are of very high quality. Like any addition of glass there is an increase in propensity to flare and sometimes a minor loss of sharpness when using a very high res back and an absolutely ideal aperture like f/8. However I, and most of our clients, are glad to accept that minor loss of sharpness in exchange for a raw file which requires minimal, if any, light fall off correction. I want to emphasize that the loss of sharpness is considered very minor by most of our clients even in a subgenre which places a very high emphasis on image quality.
Obviously some lenses benefit from it more than others, and the amount you plan to shift the lens has a very large impact on whether you need to care about this issue at all. A Schneider 47XL shot straight on (no movement) at f/11 will not show much fall off so it won't matter much if you correct it optically or digitally. But a 47XL shifted 20mm will show a lot of fall off and if you correct it entirely using LCC you will definitely notice a difference between correcting optically and digitally.
In general with the Schneider wides I recommend using a center filter unless you are handholding and can't afford the loss of light the center filter mandates, or are shooting towards the limit of the long exposure capability of your back. With the Rodenstock wides it's a trickier question.