Rodenstock is it a 90 6.8 or 5.6

[Ross Schuler]

I just purchased a Rodenstock 90mm 6.8 Grandagon. Can anyone tell me why the f s top on the lense starts at 5.6. Is it a 5.6 or a 6.8. If I meter a landscape at f22 do I use f22 on the lense. As you can tell I am new to LF. Ross

[N Dhananjay]

The lens might have been adapted into another shutter but they ommitted to change the iris scale. The quickest check would be to measure the diameter of the iris wide-open and divide focal length by this number and see if you get 5.6 or 6.8. You should get reasonably close - f/5.6 is more than 16mm while f/6.8 is about 13 mm. A difference of almost 3mm should be possible to measure with a scale or preferably a pair of calipers. Cheers, DJ.

[Jim Galli]

If it says on the lens that it's f6.8, that is what it is regardless of the scale on the shutter. Look into the glass and when you start to close down the iris when do you see the blades for the first time? Between "5.6" and 8? If so it's probably fine. I think the Rodenstock Grandagon's came in either 4.5 or 6.8, but not f5.6.

[Bob Salomon]

If you bought a remounted shutter the cells may also be out of position to each other. Rodenstock original shutters frequently have a small Rodenstock decal on the side of the shutter. If in doubt Rodenstock service in the US is 973 808-9626. They will reopen Wed.

[Jennifer Waak]

The original poster wrote to me off board b/c I have to same lens. He said that the shutter says Sinar on it and goes from 5.6 to 64. Since Sinar has lenses with shutters that are Copal 0 (as the Rodenstock is) and f5.6 to f64 I'm just assuming that it had been re-shuttered in a previous life.

So, assuming the poster has no recourse back to the seller or finds it to be more trouble that it is worth, what is the best bet? Send it to SK Grimes for a new iris to be engraved? I don't know if the buyer has recourse or not, so I'm throwing this last part out as a hypothetical.

[Steve Grimes.]

The iris scale on the shutter does not match the lens. The shutter may have been replaced/exchanged for a different one and the original scales may not have been compatible with the replacement shutter. New shutters are supplied without iris scales. It's expected that the user will take the original scales from the old shutter (along with any spacers associated with the lens) and install them to the new shutter. There are variations between old/new models of the shutters. The shutters are all accurately made and, as a practical matter can be interchanged. Its expected that attention be paid to keep with the lens elements any spacers (they look like thin washers) which may have been installed at the factory.

See: my page about engraving iris scales for more about replacement iris scales. As a practical matter f</>-6.8 is not drastically different from <i>f-5.6 and the lens/shutter may be useable as is, although you may notice some inaccuracy in the exposure similar to the innacuracy from errors in shutter speed.

[Ross Schuler]

Problem resolved The person I purchased the lense from put on the wrong shutter. Correct shutter is on the way Thanks for all the information Regards Ross

[Bob Salomon]

"Problem resolved "

Probably not. This lens needs to be checked for proper spacing in the shutter by a qualified and experienced technician. You can't simply swap shutters on wa lenses so casually and expect to have factory spec performance.

[Bob Salomon]

"Problem resolved "

Probably not. This lens needs to be checked for proper spacing in the shutter by a qualified and experienced technician. You can't simply swap shutters on wa lenses so casually and expect to have factory spec performance.

[Jennifer Waak]

</I>Fixing the HTML.