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Newbie focal length question

 
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jayjaydub



Joined: 04 Jan 2019
Posts: 13
Location: United States

PostPosted: Wed May 15, 2019 7:21 pm    Post subject: Newbie focal length question Reply with quote

Hi- I have a miniature Graflex, with a roll film back. This means framing is a bit of a "roll the dice" issue to one unused to this format. (I have no viewing (ground glass ) back. I'm using an Ektar 4.5mm 101mm lens- what would be an approximate 35mm equivalent focal length? Second ballpark question- using an ISO 100 120 color film, on an average day outside, with a 1/100 shutter speed, what would be an average aperture? (I have to start somewhere, and don't trust any of the meters I have!)
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45PSS



Joined: 28 Sep 2001
Posts: 3785
Location: Mid Peninsula, Ca.

PostPosted: Thu May 16, 2019 12:03 am    Post subject: Reply with quote

Quote:
Hi- I have a miniature Graflex, with a roll film back

That's nice, now is it a Graflex SLR, Miniature Speed Graphic, Pacemaker Crown or Speed and in what format as roll film holders were made for all 3 formats, or a Century?

What image size is the roll film holder, 6x6,6x7,6x9? Aspect ratio affects equivalency charts for lens. Search engine lens equivalent in different formats.

Search engine " sunny 16 "
It basically states 1/film speed @ f16 will provide a suitable exposure.
You can also use it as a guide to tell if your meter is lying to you or not.
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jayjaydub



Joined: 04 Jan 2019
Posts: 13
Location: United States

PostPosted: Thu May 16, 2019 4:03 am    Post subject: Newbie focal length question Reply with quote

My apologies, it's a miniature Speed Graphic. An RH10 roll film holder for a 2x3.
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Dan Fromm



Joined: 14 May 2001
Posts: 2041
Location: New Jersey

PostPosted: Thu May 16, 2019 11:49 am    Post subject: Reply with quote

OP, you're cooked. There's no guarantee that your camera's rangefinder is calibrated for the lens mounted. Without a working RF, you can't focus.

Your best bet for focusing is to find a complete 2x3 Graflok back. That's the back itself with a focusing panel. 2x3 Grafloks for 2x3 Pacemaker Graphics (Speed, Crown) are direct fits on the Miniature Speed Graphic. They're not abundant but they show up from time to time. And then there's always a chance of finding a junker with back.

To answer your question, the 24x36 equivalent focal length for 101 mm on 2x3 is 43 mm. For your 6x7 RH 10, 48 mm.

Are you sure your camera is a Miniature Speed Graphic? I ask because the RH 10 is much newer and because many people call the 2x3 Pacemaker Speed Graphic a Miniature.
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jayjaydub



Joined: 04 Jan 2019
Posts: 13
Location: United States

PostPosted: Thu May 16, 2019 2:33 pm    Post subject: Reply with quote

Thanks for the reply. Yes, it's definitely a miniature Speed Graphic with a Graflok back setup. I found the RH10 separately, can't deal with sheet film any more. I have a ground glass back, BUT, it's set up for a spring mount, so I am watching ebay, etc for a Graflok ground glass back that I can afford....might be a long wait.... if anyone wishes to trade a spring mount for a Graflok..... I don't have a rangefinder, either, so I'm hoping to focus on ground glass only. Unless, of course, a working rangefinder drops magically into my hands.

Thank you for your lens conversion info- I have mostly been a 35mm film guy, and know those lenses pretty well. Sounds like my 101mm will be a good all round slightly wider-than-normal lens.

I realize that my Speed Graphic is an uphill battle, but my slow approach is better than just junking the camera. I'm not in a rush to get it up and running, slowly accumulating the elements as I can afford them is fine by me.

I have just acquired a Busch 4x5 also, and I have a similar path. I would love a Calumet 120 roll back for that, and also a side handle. No rush, not much money.
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Dan Fromm



Joined: 14 May 2001
Posts: 2041
Location: New Jersey

PostPosted: Fri May 17, 2019 11:41 am    Post subject: Reply with quote

For most still formats -- 24x36, which is derived from a cinema format, is an exception -- the normal focal length is the format's diagonal. The diagonal of nominal 2x3 (2.25" x 3.25", 6x9 is a lousy metric approximation and is the same size as 2x3) is 100 mm. A 101 mm lens is normal for the format.

Normal for 24x36 is 43 mm. Nearly all of the lenses (50 - 58 mm, depending on the maker and era) sold as normal for it are long for the format.

Normal for nominal 6x7 (2.25" x 2.75") is 90 mm. Y'r 101 a long normal lens for that format.
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