Charles 46277 Loc: Fulton County, KY

I have a 65mm Angulon lens without shutter and a Speed Graphic camera. The Speed is a bit thicker in the back than a Crown Graphic and it seems the film to flange distance is just a bit too much for the 65mm. There are no recessed boards for these cameras.

1. What I would like to know (for this case and perhaps other cases in general), before the trouble of mounting the lens, is there a way to calculate for a given focal length (not special designs like telephoto), how much extension (film to flange) a lens needs for different distances? For instance, if I could not focus infinity (about 64mm extension), how much extension would I need to focus a 65mm lens at 8 ft, 15 ft, or 20 ft? 8ft with even moderate apertures would give good depth of field for most indoor pictures, or 15 ft outdoors would give great depth of field at f16 or f22.

2. A secondary question is, if I focus it at 8 or 10 ft, how much larger does the image on film become? Obviously, focusing close makes the film image much larger than infinity focus does, so macro work could cover 4x5--but is there a way to calculate the image circle size by the focal length and distance for a 65mm lens? At some point, the lens would cover the 4x5 negative, which is more than the 2x3 image it is made for. (I have a 2x3 back as well as 4x5.) [I won't be doing macro work with a 65mm lens on 4x5, but I might be able to cover 4x5 at, say, 8 ft.] For a start, I would like to know the extension required for 8 ft focus.

I have tried to search this, but when it comes to bellows extensions, everybody only seems interested in extensions for macro work.

By the way, I found by experiment that putting a lens extension tube on the 360mm Tele-Xenar, on the Speed graphic, not only reduces the required bellows extension, but lets the lens focus closer--8 feet for portraits is easy. But this was working with available materials, not using any scientific method. I have a 5-inch rear extension for Graflok back I could use for more extension. But adding extension is easier than taking it way (for short lenses).

ecurb1105

Do you have an Angulon or s Supef Angulon? Go ahead and mount the lens on a board. It will focus at infinity. I have used a 47mm Super Angulon on a Speed Graphic. No reason to go into mathematical exercises, experiment.

RWR Loc: La Mesa, CA

The flange focal distance for that lens is 70.5mm - you could mount it on a bellows or extension tubes with any camera, focus at 8', and measure the extension.
Edit: That is for the f/8.0 lens. The f/5.6 flange focal distance is 72.5mm.

Charles 46277 Loc: Fulton County, KY

No, as I said, it is an Angulon. The Super Angulon has a large rear element extending back toward the film (very close). I tried the Angulon in a makeshift way, and it would not focus infinity

Charles 46277 Loc: Fulton County, KY

No, the flange focal length is 63.5 (Schneider site), and the Speed Graphic is a few millimeters more than that, minimum extension.

RWR Loc: La Mesa, CA

The figures I quoted were for the Super-Angulon. You could avoid confusion by stating exactly which lens you have (coated, multi-coated, etc., as the dimensions vary).

Charles 46277 Loc: Fulton County, KY

My second question was one I have often had over the years. When lenses have limited coverage, like Rodenstock Geronar triplets or Tessar designs like Schneider's Xenar, how much does it help to focus closer (but not macro)? If all your work is in a studio, for instance, you never need infinity coverage, just closer focus. There ought to be math to show how much bigger the image becomes at closer distances--even better, a chart or Cartesian graph showing focal lengths one way and image size the other way. That way we would know before buying a lens if it suits our purposes.

For instance, the Xenar 135mm barely covers 4x5--good for press cameras. The image circle is 161mm at infinity, but if you use it in the studio at 5 to 10 feet (or less), the image would be much larger. It would be nice to know how much larger it is at different distances. Unfortunately this may not be easy because different designs have different image sizes, for the same focal length--at infinity (which is the only rating given). Why can't manufacturers give us tables that show image size at different distances--say 4ft, 8ft, 16ft, infinity? (f16 would be fine.) They give us depth of field charts, yes?

Charles 46277 Loc: Fulton County, KY

I said Angulon 65mm, to start--there was only ever one of these. It was an f6.8. This one is coated, but that does not change the question.

RWR Loc: La Mesa, CA

That one really goes way back! Mine is the f/5.6, military surplus, no lens ID or serial number, but the leaflet that came with the kit says it’s multi-coated, which changes the flange focal distance (72.5 vs. 71mm). It would be nice if Schneider provided more information, but you can easily determine the coverage and extension required for any distance by using a ground glass focusing screen (off the camera, of course). Sounds like an interesting experiment. Good luck1

User ID

All same FLs have same IMAGE SIZE. They WILL vary in
circle of coverage. A 210 zoom from Nikon makes the same
size image as a 210 Symar, but the Nikon may grab a tight
head shot while the Symmar on a 4x5 grabs a 3/4 length
portrait. One shot sells a hat, the other sells a jacket.

OTOH actual increase in image size due to focusing closer
is real. And the math is easy cuz it's linear. Say you have a
100mm image circle but the film is 4x5. So, you need 150
mm image circle to fill most of it. Extend the lens to 150%
of it's infinity position and you get 150mm circle from the
lens that had only 100mm circle at infinity. Linear means
you could extend the lens to 125% of the infinity position
and get a 125mm image circle.

Suppose you extend your 65 angulon by 10% [as your
Speed Graphic forces upon you ... approximately]. BIG
THING: Percentage of extra extension is PERCENTAGE
of the FOCAL LENGTH.

So, your flange distance for infinity is 63.5 for an angulon
but is 70 for a the Super. Ghese are just FLANGE distances
due to shutter dimensions etc etc. For EITHER version, the
FL is 65mm so a 10% increase in flange-to-film distance
means you "rack out" 6.5mm past the infinity position. We
DO NOT CARE that infinity focus extension varies by lens
design. We only care to know the ADDITIONAL extension
for that FL.

Now that the measurement points are understood ... linear
math means if add 10% extension [110% of infinity focus
extension] then the image circle AND the ACTUAL IMAGE
SIZE is now 10% larger.

As to what the focus distances will be for various FLs at
various increases in extension beyond their infinity position,
you apply a formula that I hafta look up cuz I have no real
reason to memorize it. If you had trouble searching for it
I imagine you used the wrong key words. The correct key
words are scattered throughout the post you've just read ;-)


`

Charles 46277 Loc: Fulton County, KY

Yes, it was made in the 1960's--fully coated but before multi. But I don't think it has ever been used--looks new.

p.s. I have a Graflok adapter plate accepts to a Canon camera, but this won't work for wide angle--it adds a couple of inches to the bellows length. I have a barrel Zeiss 250mm and a 300mm that could be used that way, using the Graphic shutter or the Canon shutter.

Charles 46277 Loc: Fulton County, KY

Yes, I understand most of what you say--but when I talked about image size, I was not referring to magnification of the subject, but merely the size of the circle of coverage. It would be useful to know this for certain key distances (before buying the lens). This circle is larger as you focus closer, so if you just use it indoors, you have a much larger circle than the specs will say.

There is no direct relation between the size of the image circle and the focal length of the lens.

You are right that subject magnification is related directly to lens extension over and beyond its focal length extension (infinity). I was able to approximate in this way, using the 65mm lens with 4x5 film. (Pretend here the flange distance at infinity is 65mm even, or find the true focal center and measure from that...)
If the extension is double the focal length (add 65mm to 65mm), the image size is life size--that is a subject 4x5 inches in size will fill the frame.
Add half that (add 32mm to 65mm), the image is half life size--a 4x5 subject covers half the frame.
Add half that (add 16mm to 65mm), the image is 1/4 life size--a 4x5 subject is 1/4 the frame
Add half that (add 8mm to 65mm), the image is 1/8 life size==a 4x5 subject is 1/8 of the frame
Add half of that (add 4 mm to 65mm), the image is 1/16 life size--a 4x5 subject is 1/16 of the frame.

I see no way to predict the focusing distance (subject to film) from these figures.

The last figure approximates the close focus of many standard lenses, and aperture could give hyperfocal distance settings. With a wide angle lens, that may also be true of the 1/8 settings.

These numbers address magnification, but do not tell us distances unless we test measure distances for each extension. However, I think we would find that any 65mm lens will have the same distances of focus at each level of magnification (unless the lens design is tele- or wide). Tables of these numbers could be useful, as they would apply to all lenses.

Probably my best solution in this case is just to mount the Angulon in a flange attached to the back of the Graphic lens board--the lens can screw in, still facing forward. A rubber or cork washer between flange and board would bring it back a tad more. The lens settings would still be reachable and movable, as barrel mount lenses are almost entirely in front of the flange. Then I could focus on any reasonable distance and let aperture take care of infinity. Unlike the Super Angulon, the Angulon was Schneider's improved version of the Dagor design (6 elements, somewhat symmetrical--often called the "Reverse Dagor) because putting the rear element forward gave wider angle of view without vignetting. So it is quite suited to macro work on its own, except in this case for being so short.

User ID

OK. I ran the search. There was a word NOT used
in my post btt was a very helpful for a keyword to
produce a quick search result. Word is: "Calculate".

If you wanna read more, search string I googled is:

"calculate subject distance based on focus extension"

Quickly turned up this formula:

1/FL = 1/subject distance + 1/image distance.

Reminder: Use consistent units-of-measure :-)

BTW, the subject distance above is from the lens,
not the film plane. Notice the inversions [1/X].
The diopter number of a lens is the inverse is
the inverse of its FL-in-meters. IOW a "+2" close
up lens has a FL of 1/2 meter. When you see a
weak close up lens designed for long tele lenses,
it may have a "model name" such as "Canon CU
lens 2500", you can bet it's a 1/4 diopter lens,
having FL of 2500mm [2.5 meters]. 1/4 diopter
is a typical accessory for a 300 or 400mm tele to
bring its near limit closer than the 12 to 20 feet
typical of long teles [older ones anyway].

`

User ID

I'm olde skoole, and old in years,
so I HAVE that book of tables !

BTW, doesn't matter about wide or
tele design when dealing with the
question of ADDITIONAL extension
past the infinity position. Wide and
tele designs alter the inf'y position
relative to the film plane, but the
additional extension BEYOND that
inf'y position is not affected by a
retrofocus or a true telephoto wide
or tele design. IOW your 360 Tele
Xenar and a 360 Symmar will both
need the same increase to move
from inf'y to some given subject
distance, even tho the inf'y focus
bellows extension for the Symmar
is about DOUBLE that of the Tele
Xenar ... despite their equal FLs.
My book of tables doesn't ask for
the type of lens design. It works
by FL only.


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Charles 46277 Loc: Fulton County, KY

Good to know--makes sense.
What book--you mean table of extension for distances?