XPan center filter on 65mm 4.5 Grandagon?

[PKM-25]

I am mulling over the idea of getting a 65mm 4.5 for extreme wide angle work, partially because either the Rodenstock or Caltar N versions use a 58mm filter thread that is shared with my 180mm Apo Symmar.

I have a spare 58mm 1.5x center filter for my 30mm Xpan lens that could in theory work. The only concern would be would 1.5x be too much central density and would the filter cut into the corners since the design is odd in that the actual glass is a few mm smaller in diameter than a normal 58mm filter.

The Xpan lens is pretty much as wide a taking angle as the 65mm, around 17mm and the filter does not cut into it....but it is also panoramic aspect ratio. I guess I could always just give it a try...

 

[David A. Goldfarb]

1.5x won't be too much. The only question would be whether there is something in the physical design that reduces the image circle.

In general, I think people make too much out of the idea that center filters are precisely matched to their lenses. A precise match would usually be impractical, because it would require too much exposure compensation at f:22--the usual recommended aperture--plus reciprocity, so most center filters represent a compromise of what is practical with what constitutes an aesthetically acceptable or even desirable amount of falloff of illumination, and usually that amounts to something in the range of 1.25 to 2 stops, while 100% compensation would usually be around 2.5-3.5 stops.

 

[PKM-25]

Thanks David,

I bought a like new 65mm 4.5 Caltar II N for a good price, I bet 1.5X would be fine as I only shoot black and white in 4x5. One of the reasons I am wanting this lens is that if I need to work wide and start off in lower light, the F4.5 will be much easier to focus that my 90mm 6.8.

I did a little sleuthing and found that the recommended Rodenstock center filter is a 58mm male thread with a 77mm front female thread allowing for some degree of filter stacking without the 2nd filter showing up in the corners.

The glass in XPan 58mm filter is therefore closer to the front element...maybe it will not vignette...I'll soon find out.

 

[Dan Fromm]

Um, lost-and-gone-forever, the recommended center filter has such a big piece of glass so it won't vignette. But since you have the XPan center filter, you might as well try it.

 

[LJH]

I used an Xpan CF on a Schneider 65mm (it was on a converted Polaroid 6x12cm camera).

Worked well; however, I wasn't really pushing the image circle with that format, so cannot confirm that there won't be mechanical vignetting on 4x5.