Rodenstock 80mm heligon and flare

[tedw6]

I recently purchased a Rodenstock 80mm f2.8 heligon for use on a 2x3 camera. It is stunningly sharp and I'm happy with it. However, I've had a couple of shots showing what looks like a flare that runs all the way across the image.

The filter screw is 40.5mm and I've got a 40.5-49mm stepup ring installed to be able to use 49mm filters.

What is the angle of view of this lens? I want to use a lens hood to deal with this flare and want the longest possible lens shade, ideally a 49mm screw-in for a telephoto lens on a 35mm camera. If I use this, will I impact the angle of view?

Thanks.
Ted

[Phil Hudson]

One way to test which lens hood you need is to focus the camera at infinity with a bright uniformly lit scene. Stop the lens down to f/16 or f/22 and view the image on the screen. Assuming you won't be using movements use the narrowest/longest hood that does not obstruct the image (at small apertures the edges of the hood should be sharp and easily seen).

If you wil be using movements your choice of lens hood will have to be adjustable, not rigid.

[aduncanson]

There are several reasons why you really cannot answer the question that you should be asking without more information, in fact you would need information that is not commonly available, even for popular, in-production lenses.

First off, the size of 2 1/4 x3 1/4 or 6x9 backs is pretty variable. My graflex roll film back measures 57x78mm. My Horseman measures 57x82. An old wooden graflex sheet film holder measured 56x78. (Since you asked, the angle of acceptance for these film holders would be 62.3, 64.0 and 62.0 degrees respectively. - Now are the holder's film apertures centered on the axis of the lens. That might come into play and would depend on your camera.) Coverage for the 80mm Heligon is going to be tight on 6x9, so I will assume that you do not intend to use camera movement.

The remaining unknown is what point to construct your angle of acceptance from. The answer is the entrance pupil, but its location (say its distance ahead of the film plane or back from the filter ring) is not generally disclosed.

The upshot is that it is best to not try to finesse this with too much mathematical analysis, but to experiment. Most likely you will not get by with a hood made for a telephoto lens, but rather will require one made for a 35mm focal length lens on a 35mm camera. (35 / 43 = 80 / 100 - 43 and 100 mm being the rough negative diagonals of the two formats.)

For optimal results you might need to get an adjustable hood like (perhaps) the LEE lens hood.

Good Luck - Alan

[leighmarrin]

Ted, should you take Alan's advice about a lens hood for a "normal" lens, Fedka.Com in New York City has six different inexpensive types of 40.5mm lens hoods. I have one of their collapsible hoods, but usually forget it to use it when using my uncoated 5cm/f2 Sonnar..

http://fedka.com/catalog/index.php?cPath=40&osCsid=e85617953c157a22e802f7af873282ed

[ic-racer]

, ideally a 49mm screw-in for a telephoto lens on a 35mm camera.
Thanks.
Ted

Wide angle lenshood. Like for a 35mm lens. Or get a 'standard' hood and file the corners until they don't vignett. If your groundglass corners are clipped it is easier to test the edges.

[Mark Tweed]

Ted, your Heligon is a 6 element Gauss construction, it's Rodenstock's answer to Zeiss's Planar and Schneider's Xenotar. The coverage is around 60 degrees so I'm surprised your 80mm Heligon covers the 2x3 format. I have the 100mm version for my 2X3 Century and it covers the format with limited room for movements. I would have thought the 80mm was appropriate for the 6X6 or 6X7 formats. And yes, I always use a lenshood with my 100mm and so I haven't noticed a flare problem.

Try the lenshoods the other members have suggested. You can test whether coverage is being blocked with the hood by simply looking from the back of the camera at the film plane (much like viewing from the cut corners of a ground glass on a view camera).

Enjoy your fine lens, it's a rather rare gem.

Mark