150mm LF lens

[Ho Pei Jiun]

Dear Sirs/Mdms,

I've another question:

If i want to focus the Rodenstock Rodagon Apo-Sinaron-N 150mm large format lens at infinity, do i need to use the detachable rear element of this 150mm LF lens?

Please kindly advise. Many thanks.

Sincerely,
Ho Pei Jiun

[Ted Harris]

Yes, absolutely you need to use the rear element. The front and rear elements of modern large format lenses are detachable to allow mounting the lenses in the shutter.

You can use the rear element by itself. That is you can remove the front element. The lens i snot designed for this use bu can be used this way to give you a longer focal length if you want to play around. If you decide to do this remember that your aperature scale will no longer be accurate, it will be off by about 2 stops.

[Chris Gittins]

Remove both the front and rear elements and stop down as much as possible. The aperture should be no larger than 1 mm in diameter. That combination will provide good focus at infinity.

[Dan Fromm]

Ho Pei, in my dialect of english the first two replies told you that you're an idiot.

Less insultingly, you need the whole lens. The front cell and rear cell were made to be used together.

Good luck, think more and ask less,

Dan

[Andrew O'Neill]

Gee Dan, are you ever rude! You are obviously a rascist too. So when you saw your first LF lens you knew exactly what it was and how to use it??? YOU are the idiot.

[Witold Grabiec]

It's a wonder what kind of brain thinks MORE and asks LESS.

Ho Pei - don't get discouraged, ask at least as much as you think. It's the only way to PROGRESS.

[Nature Photo]

Ho Pei:
I am by far not an expert on this subject, but I know that there are lenses (called 'convertibles') which have different focal lengths if you selectively uses the front or back element or combinations thereof. For example, the Cooke Triple Convertible or the Wisner Plasmat convertibles.
The lens you mention is not a convertible, thus you'll need both elements and the shutter between them. To focus at infinity, you extend the camera, so that the distance between the film plane and flange (=lens) is equal to the focal length, that is 150mm or thereabout.

[Dan Fromm]

Andrew, I translated. I didn't call Ho Pei names, the first two posters did. Excoriate them, not me.

Now tell me, Andrew, are modern 6/4 plasmat type lenses such as Ho Pei's Apo-Sinaron-N separable? Mine aren't and his isn't. That's why I read the first two replies as thinly disguised insults.

If you'd been paying attention, you'd have noticed that Ho Pei has been asking essentially the same question for some time now. He seems not to have understood the answers or, perhaps, not got one that told him what he wanted to hear.

Racist? Where did you get that tripe? This is more anglophone, possibly white man's, 'expletive'.

As for being an idiot, of course I'm an idiot. Its a bad day when I haven't heard "Don't be such a 'expletive' idiot" from my colleagues at least three times. But unlike you I know I'm an idiot. And unlike you, I've learned to read and to seek information from books, not bulletin boards. Bulletin boards are sometimes good ways to find obscure facts. The bulletin board is a poor medium for learning technique, which includes "how things work."

Cheers,

Dan

[Andre Noble]

That's a modern lens. Who would think of removing the rear element to shoot with it?

Reminds me of the really basic questions my younger brother used to ask as a kid just to get attention.

[Andrew O'Neill]

Dan, Ho Pei is obviously someone who knows very little about modern 6/4 plasmat lenses or LF for that matter. Still no need to call him an idiot. OKay, maybe you are not a rascist...you came across as one, though. The point of this forum is to help.