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Open to questions on diopter lenses

 
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Telek guy



Joined: 10 Mar 2004
Posts: 10
Location: Kalamazoo, Michigan

PostPosted: Thu Mar 11, 2004 3:41 pm    Post subject: Reply with quote

Hi group, I'm the author of the Nov./Dec. "View Camera" magazine article on using diopter lenses to change focal length on large format lenses. I'm open to questions.

[ This Message was edited by: Telek guy on 2004-03-11 07:43 ]
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Fri Mar 12, 2004 3:50 am    Post subject: Reply with quote

Welcome! Glad to see you got your posting problems solved.

We had quite a good discussion of using suplimentary lenses in a couple of other threads. Some people like them, some don't. And we brought up the question of trying to use a positive diopter to create a shorter focal length lens and wondering about the results. Since we all have used "close up lenses", I for one have never thought of this use.

Now, I have an admission and an apology. In the other thread, I mentioned that I had never heard of anyone using a + diopter to create a shorter FL lens. Now here I am being a bit red faced... I hadn't yet read your article. These past couple months just have not allowed me the time to keep up... So I just gave the article a quick read.

Not only agreat article, but it pretty much answered all my questions! Now all I have to do is find the time to get out and try some of this. On the other hand, if we had all read the article, we would not have had the discussions There's some good in it all!

I'd also like to try a newly acquired negative diopter on an already long lens to see how it does. It can be fun pushing the limits. And boy those - dipters are hard to find!

Thanks for the great article! I will give it a _good_ read a little later!


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Telek guy



Joined: 10 Mar 2004
Posts: 10
Location: Kalamazoo, Michigan

PostPosted: Fri Mar 12, 2004 6:49 pm    Post subject: Reply with quote

It's nice to talk to some kindred spirits. I had a couple of responses to the article by those in need of larger size (diameter) diopter lenses. One individual ended up having a local optician who happened to have a couple of 3 inch diameter blanks grind a minus 1 lens for his huge lens fitted to a 12x20 camera. It cost him $90 which included coating. He said it produced a great visual image but I have not heard what kind of negative it produced. Since he was making contact prints I suspect that sharpness was not a problem.

Though I've used these lenses on 4x5 I would expect super results on larger formats that are contact printed.



[ This Message was edited by: Telek guy on 2004-03-12 10:52 ]
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Fri Mar 12, 2004 7:34 pm    Post subject: Reply with quote

I suppose having the lenses made is an option, but I'd hate to spend that kind of money, not that I can at this particular moment anyway...

I would love to have a set of minus diopters in 72mm, 77mm or larger. I don't remember what size my larger diameter lenses are? I think a 77mm would cover most of them. Unfortunately, the only long lenses I have for 8x10 are the convertables. Luckily, they are a rather small diameter.

Searching for diopters is no easy task since the word is so common in corrective lenses. Adding "tiffen" to a search produces no results. The minus lenses are next to impossible to find...

I collected my film & holders today and hope to shoot a couple of tests this weekend. "New" (1928) camera, a lens that probably won't work, a few that do, and a new Tiffen minus 4 to play with.


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worldphoto



Joined: 05 Feb 2003
Posts: 199
Location: Southern California

PostPosted: Sat Mar 13, 2004 7:25 am    Post subject: Reply with quote

The chances of my ever owning another LF lens/shutter is some where between slim and none. Your article and diopter lenses have given my LF photogtaphy new life. Diopter lenses look, feel, fit and are listed under filters on eBay. So in my home I can call them filters and it's alright to buy filters.
Other than the ones you've mentioned... Have you learned of any new sources of minus lenses?
Harry
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Telek guy



Joined: 10 Mar 2004
Posts: 10
Location: Kalamazoo, Michigan

PostPosted: Sat Mar 13, 2004 3:50 pm    Post subject: Reply with quote

We have local photo flea market type sales here about twice a year. The diopter lenses are usually mixed in with the filters. Couple of months ago I saw a set of the Teleks in a nice box for about $20. Usually they are cheaper because they are small and the sellers think they are some kind of odd filter. Never see any of the series 7 sizes. By the way in response to using them with larger diameter lenses; I've used them on the rear of the prime lens. Many times the rear mount is smaller than the front. I've blackened the shiny parts with matt lacquer to prevent reflections. In fact the authorities think they work better on the rear of the lenses. I've seen no differences.
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worldphoto



Joined: 05 Feb 2003
Posts: 199
Location: Southern California

PostPosted: Sun Mar 14, 2004 4:56 am    Post subject: Reply with quote

The idea to grind your own large diameter minus lens sure makes sense. Now to find someone to do it in San Diego. I'm not sure if it's available here for $90? The question: What coating should one spec and/or what is it correcting?
Harry

[ This Message was edited by: worldphoto on 2004-03-14 09:26 ]
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Sun Mar 14, 2004 5:26 am    Post subject: Reply with quote

Heck, I'd be happy with no coating... That's what we get with the old 'filters' anyway.

I know one problem around here. The past two times I got new eye glasses, they had to be special ordered because noone does glass grinding anymore. All they do is plastic now. And I wonder if an optical plastic lens would be worth it? A bit less scratch resistant for sure though.

And if there's a discount to having more than one made, LET ME KNOW!!!


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worldphoto



Joined: 05 Feb 2003
Posts: 199
Location: Southern California

PostPosted: Sun Mar 14, 2004 7:18 am    Post subject: Reply with quote

Oh, I will Rich, I don't keep quiet for too long. The problem I have here is that we've been going to medical doctor eye consultants (ophthalmology) for about twenty years now. It costs about a hundred just to chat with them. There is always the telephone and telescope suppliers. I figured that a -1.3 diopter lens would get my 360 to just over 600mm and still have some bellows left. A -2 diopter calculated out to about 950mm. Way too long for my 30" bellows. A -1 will only get me slightly over 500mm.
I've tested the series 9 positive lenses on the rear element and it worked great. Couldn't get full coverage with the +3 but will work great on a 5x7 and 4x5. The +2 seems to give me full coverage on the 8x10. I keep getting disconnected so I'll say GN, Harry

[ This Message was edited by: worldphoto on 2004-03-13 23:43 ]

[ This Message was edited by: worldphoto on 2004-03-14 19:14 ]

[ This Message was edited by: worldphoto on 2004-03-14 19:32 ]

[ This Message was edited by: worldphoto on 2004-03-14 20:45 ]

[ This Message was edited by: worldphoto on 2004-03-14 21:05 ]

[ This Message was edited by: worldphoto on 2004-03-16 06:21 ]
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