Graflex.org

DenisP · Joined: 14 Oct 2002 Posts: 43 Location: Croatia, Europe

Hi everyone,

I'm back with a quick report and a few questions again...

I've got a Pacemaker Speed 2x3, and I've successfully managed some DIY lens mounting exercises - see my post sometime ago on Lenses forum ("Rolleiflex TLR lenses on PSG 2x3 - UPDATE!"). So, managed to use a Xenotar 80/2.8 on my Speed, with excellent results.

Some time ago I purchased a "Repromaster" 210mm barrel lens - I guess it's a flat field, that was used on some kind of repro camera.

Since it's not a tele design, my bellows were too short to focus this beast much closer than infinity, so I made an "extension lensboard" (using some PVC piping that I had on hand), and now the closest I can focus is about 1,3 m (some 4,2 feet), which is much more usable. The ground glass image looks just fine, clear and no vignetting.

I was thinking that it might be handy for portraits.

However, I'm not sure whether I'll need to include some extra bellows factor into the exposure calculation.

The lens is 210 mm (f9 to f128)and when focused on infinity with the "extension tube", the back element of the lens is about 20cm from the film plane.

Now, do I just set exposure as indicated by the meter (e.g. 1/60 at f

, or do I need to add bellows factor?

For those interested, the lens looks like the one currently on eB** (#2947826745), with the only difference that mine is 210mm.

Regards,

Denis

[ This Message was edited by: DenisP on 2003-08-27 08:22 ]

RichS · Posted: Wed Aug 27, 2003 4:49 pm Post subject:

Congrats on your ingenuity!
As far as bellows factor, no, you don't need any. Any mounted lens, focused at infinity is working as designed (f9 in your case). Even if you mounted a 30 inch lens with two feet of tube, it would still need no bellows factor when focused at infinity.
The general rule (as I remember) is not to worry about a bellows factor at anything focused over six feet. Less than six feet is minute until you reach a one to one ratio where it's 2 stops. One to one on your lens would be 420mm of bellows or 16.5 inches...
So don't worry about it unless you figure out how to make the bellows even longer...

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Nick · Joined: 16 Oct 2002 Posts: 494

My understanding is the repromaster is just one of the names used by Agfa for thier process lenses. I have a Super intergon which is supposedly the same lens but different name. On mine it came with a handwritten exact focal length of something like 209.2 mm. Which gives you an idea these weren't cheap lenses when new. Today they are more or less being given away.

Assuming the repromaster is the same lens then it's a wide field process lens. Coverage for the 210mm should exceed 8x10. Process lenses tend to be designed to be used at F/22 .

worldphoto · Posted: Wed Aug 27, 2003 6:37 pm Post subject:

Denis
Making the proper exposure is very important. Making sure your light meter is properly set is also important. John Shaw's book "Closeups In Nature" has a good chapter on calibrating a light meter and all it takes is using the sunny f/16 rule.

All camera lenses work the same way when the lens is moved out more than half again its focal length from its infinity setting. The amount of extra exposure depends on the inverse square law. You simply find out how many times the old instance goes into the new, and square that number. That will be your new exposure factor. For example, if you're using a 6 inch (150mm) lens focused at 12 inches (300mm) , you divide 12 (300) by 6 (150), which gives you 2.0: you multiply that by itself, and your answer will be 4 which, is your exposure factor. Take the square root of the exposure factor and you need to change your lens speed or aperture by 2 stops.

Ok, why use exposure factors? What if you also were using a filter with a filter factor of 4. Now, using the above example, you have an exposure factor of 4 and a filter factor of 4, you would have a total exposure factor of 16 (4 times 4 equals 16). The square root of 16 is 4 so you need to open up the lens aperture by 4 stops or reduce the speed by 4 stops.
Work and think with exposure, filter factors and stops and it will help you in everything you do in photography.
Harry

[ This Message was edited by: worldphoto on 2003-08-27 11:50 ]

[ This Message was edited by: worldphoto on 2003-08-28 09:16 ]

45PSS · Posted: Wed Aug 27, 2003 9:38 pm Post subject:

Denis,
Another rule of thumb that gets one in the ballpark of correct exposure is:
Lens focused at infinity = calibrated meter reading. See Ansel Adams book THE NEGETIVE for film testing/meter calibration procedures. Each meter/film/shutter combination will be different.
Lens focused closer that infinity = calibrated meter + lens focused distance - infinity focus distance/infinity focus distance. The rear nodal point of the lens is the correct reference point but it varries with each lens. Most using this method just use lens focal length and the rear of the lens board at the lens mount to the film plane for measurements.
So if your extended lens board lens focuses infinity at 209.6mm (20.96cm) and you are focused at 212.3mm (21.23cm) you would need to add 212.3-209.6/209.6 = 2.7/209.6 = .01288 f stops more exposure. Most say it's not necessary to consern oneself with amounts less than .33333333333333333333 stops.
Charles

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The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

Micah in NC · Joined: 26 Jun 2003 Posts: 94 Location: North Carolina

Harry,
I'm glad you explained the bellows factor! (I am printing that out for handy reference, btw!).

As you all may know, I'm really still new to Graflex photography, but I'd love to try some closeups with my Pre-Ann 4x5 S.G. Hmmm, wonder how close those bellows will let a 127mm Ektar focus???

Sounds like a good excuse to open up the Graflex soon!

--Micah in NC

worldphoto · Posted: Thu Aug 28, 2003 2:35 am Post subject:

Micah
That can all be calculated very simply.

Magnification equals length of bellows extension beyond infinity divided by the focal length of lens.

M = E/F

For example, to work in inches, change 127mm to 5" and then a 10" extension beyond the camera's infinity setting would make for a 2X full size magnification. You would need around 15" from the film plane or ground glass to the lens.

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Or you do like every table top pro shooter I know does...... take a meter reading, guess at what you'd think is about right for the amount of bellows extension, then shoot a polaroid.

Unless your shooting really close up---1:2 or closer then the 1/2 to 2/3 of a stop is fine. If you shoot neg then add a bit more, if you shoot chrome add a bit less, then bracket.

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45PSS · Posted: Thu Aug 28, 2003 6:00 am Post subject:

Is there a simple way to calculate the distance the subject must be to be in focus? If a 150mm is positioned at 250mm then subject(s) at "X" distance will be in focus.

_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

DenisP · Joined: 14 Oct 2002 Posts: 43 Location: Croatia, Europe

Well, as for my original question, here's an update:

I managed to put together the Repromaster lens and the DIY "extension lensboard", and the thing functions just fine.
I shot a roll of EFKE R100 today, and the negs came out excellent. I shot a tabletop arrangement (wine glass and some fruit on a black backdrop), from a distance of approx. 1,3 metres (4.2 feet).
No bellows factor used.
I shot it as the meter indicated - I have a Sekonic Studio Deluxe (incident meter), and I just used what the meter indicated: all the negs were just fine - apertures were from 11 to 22.

So, the DIY tele definitely works - now I have a moderate tele lens for a reasonable price (about $50) and about an hour's work on the lensboard.

Not bad

Regards,

Denis

[ This Message was edited by: DenisP on 2003-08-28 16:10 ]

worldphoto · Posted: Fri Aug 29, 2003 3:05 pm Post subject:

Another View! Limited bellows and long lens as above. Use closeup lens which will shorten the effective focal length of the lens; with a +3 closeup lens the 210mm prime lens becomes a 129mm lens. The focus distance from the lens to the object becomes about 0.33 meters and the magnification is about 0.6X life size. Stop down prime lens to increase DOF and improve image quality. Now you have extra bellows to vary magnification and focusing distance.
Harry
No exposure compensation required because there isn't any loss of light.

A +1 closeup lens will focus at 1 meter, a +2 closeup lens will focus at 0.5 meters and the +3 will focus at 0.33 meters when the prime lens is focused at infinity.

Doubt there is much interest in closeup lenses but I use Series 9 diopters for all my lenses except the one that requires a larger than 82mm filter.

[ This Message was edited by: worldphoto on 2003-08-29 08:21 ]
[ This Message was edited by: worldphoto on 2003-08-29 11:05 ]

[ This Message was edited by: worldphoto on 2003-08-31 12:12 ]

Dan Fromm · Joined: 14 May 2001 Posts: 2120 Location: New Jersey

DenisP · Joined: 14 Oct 2002 Posts: 43 Location: Croatia, Europe

Dan Fromm · Joined: 14 May 2001 Posts: 2120 Location: New Jersey

worldphoto · Posted: Wed Sep 03, 2003 3:02 pm Post subject:

Charles
Regarding your question about... "Is there a simple way to calculate the distance the subject must be to be in focus?" On pages 6 and 7 of Harold Merklinger's book "The Ins and Outs of focus" there is a formula and graphic means to solve for the above distance. I have played with both the formula and the graphic and came up with an answer of 375mm.
The above book is now a shareware and is available for download at his web site. If anyone is interested.
http://www.trenholm.org/hmmerk/
Harry

[ This Message was edited by: worldphoto on 2003-09-03 08:54 ]