Question about what seems to be a lens accessory

[coisasdavida]

I found this in a box of Linhof parts I got recently.
Looks like a drop-in aperture disk. But for what 210mm lens?

https://c1.staticflickr.com/1/601/32381990611_c375bd25c9_c.jpg

https://c1.staticflickr.com/1/473/31692172573_819366eac8_c.jpg

Goes from f/90+1/2 to f/256
Only marked "f=210", nothing else.

Thanks!

[coisasdavida]

Can a moderator add the "be" missing from the title?

Fixed! ...Oren

[IanG]

Looks like a 210mm FL pinhole lens and those are the apertures.

Ian

[Bruce Watson]

Looks like a 210mm FL pinhole lens and those are the apertures.

I agree.

[Greg]

I beg to disagree because I have seen a very similar item years ago and is was a multi waterhouse stop for a process lens. Also the optimum aperture for 210mm is f/392 not f/256 as mentioned in the original post. But hey.... I could be wrong.

[Jim Jones]

Looks like a 210mm FL pinhole lens and those are the apertures.

Ian

I also disagree. A pinhole for a 210mm focal length would be .646mm according to the Lord Rayleigh formula, which gives a slightly larger pinhole than many photographers choose. The aperture in the unidentified item looks much larger. Also, f/90 pinholes would be appropriate for focal lengths of about 16mm while f/256 pinholes would be appropriate for pinhole focal lengths of about 130mm.

[IanG]

I also disagree. A pinhole for a 210mm focal length would be .646mm according to the Lord Rayleigh formula, which gives a slightly larger pinhole than many photographers choose. The aperture in the unidentified item looks much larger. Also, f/90 pinholes would be appropriate for focal lengths of about 16mm while f/256 pinholes would be appropriate for pinhole focal lengths of about 130mm.

But there's no other explanation when it's clearly marked with a FL and f stops, those stops are too small to be used as rotating stops in a 210mm glass lens.

I wonder if this was part of a kit, a bare lens tube that could take different FL versions, it does look like it would fit a tube like a Waterhousue stop.

Ian

[Jim Jones]

One of many possibilities would be a device for studying the performance of a 210mm lens in the aperture range where diffraction becomes significant. Such a device might be useful in schools or optical labs. However, the range of apertures seems too small for this, and somewhat large for pinhole imaging in visible light. Although the device seems intended for one focal length, it could be applied to any focal length with appropriate scaling of the scales. If Guilherme can provide us with a close-up of the aperture plate with a scale for reference, our calculations can be more accurate.

[DrTang]

to me, it looks relatively modern (50's - 70's) ..if that helps any

[coisasdavida]

I beg to disagree because I have seen a very similar item years ago and is was a multi waterhouse stop for a process lens. Also the optimum aperture for 210mm is f/392 not f/256 as mentioned in the original post. But hey.... I could be wrong.

Greg's idea got me thinking and I went after a Repro Claron's barrel I had. This barrel was for a 355mm, there is a slot for a waterhouse stop of some kind, the thickness of the slot is a perfect fit. The acessory is too narrow to take the entire slot, but is fits nicely against one side. I bet the 210mm Repro-Claron being a smaller lens (smaller shutter size) has a narrower slot. Thank you so far!