Focusing questions

[welly]

Hi guys,

So I've got this Sinar F2 all set up. I've set all everything to zero and I have my 90mm lens fitted to the camera. I just have it set up in my front room so really just capturing about 20ft of space in front of me. I'm finding that unless the standards are almost right up against each other, then there's nothing in focus. Any thoughts/suggestions/advice?

Thanks!

Welly

[Armin Seeholzer]

So at about 10 cm distance between the front and back standard you should have it sharp, maybe even a bit more because its not infinity!

Hope I did understand your question right. Armin

[Gem Singer]

Something is wrong.

With a 90mm lens, focus should be achieved (at infinity) when the lens and ground glass are approx. 90 mm apart(the focal length of the lens). At twenty feet, they should be farther apart than 90mm.

[Bob Salomon]

Wide angle bellows? Recessed lens board or reversed front standard?

[percepts]

is the lens rear element the right one for your front element?

Assuming a non recessed lens board, then a 90mm lens will be less than 4 inches from film plane at infinity. Further when focussed at 20 feet but not much further.

[williamtheis]

if you need a Linhof style recessed board (copal 0), I've got one for sale

[Oren Grad]

A 90mm lens may be just about at the limit of what can be focused with the standard bellows. Can you post a snapshot of your setup focused as you've described it?

[welly]

Actually looking at it, it's probably about 9cm between the front and rear standards.

This is how it's looking when it's in focus.

http://i50.tinypic.com/256ha4y.jpg

I'm guessing a wide angle bellows or a recessed lens board might help and give me more movements with this lens?

[rdenney]

I'm guessing a wide angle bellows or a recessed lens board might help and give me more movements with this lens?

The cheapie ebay recessed boards for Sinar won't provide much room to operate the controls of a #0 shutter, and if it's a real Sinar recessed board, it might not even fit.

The bag bellows is a MUCH better choice for about the same price. Remember that Sinar and Horseman use the same bellows system, so the bag bellows for either one will work.

One reason I switched from the Cambo to the Sinar was to allow flat boards with lenses down to 65mm. With the Cambo, I had to use a recessed board with the 90, and even though that board is larger with a much larger recessed area, it was annoying.

The wide variation in bellows length when changing focal lengths is often a surprise to first-time large-format users. Much effort in the design of a view camera goes into fulfilling requirements for focal range. The Sinar really shines in providing flexibility, even to the point of extending the rail inserting a multipurpose standard to connect two bellows end to end for really long lenses.

Rick "who uses everything from 47mm to 305mm on a Sinar" Denney

[welly]

The bag bellows is a MUCH better choice for about the same price. Remember that Sinar and Horseman use the same bellows system, so the bag bellows for either one will work.



Off to the For Sale/Wanted forum I go then :) Aside from that, judging from the photograph I posted, does that look reasonable for a 90mm lens? I don't have a ruler to hand but I'd say that from the front of the front standard to the rear of the rear standard, that's a good 90mm.

[Gem Singer]

Alastair,

Looks normal for a 90mm lens.

Your original remark that the standards were almost right up against each other was a misleading over statement.

[jan staller]

It's reasonable to have your standards that distance if your lens is focused! Bag bellows are the only way to use those shorter lenses for interiors and landcapes. I doubt that you can shift that lens in any direction using the conventional bellows.

[rdenney]

Aside from that, judging from the photograph I posted, does that look reasonable for a 90mm lens?

Rick "yes" Denney

[welly]

Alastair,

Looks normal for a 90mm lens.

Your original remark that the standards were almost right up against each other was a misleading over statement.

That would be panicking thinking I've done something significantly wrong! :) It was perhaps an exaggeration.