MattKing
Moderator
Maybe because it only works if the lenses used were made by the camera's manufacturer, and explicitly identified as working with the scale.
The idea about the ruler is good though.
I have the same Mamiya RZ67 and the chart works fine, it's a wonder to me they didn't incorporate the same sort of chart on all modern LF cameras, it seems kind of like a no brained to me, but no one's done it yet, I mean the least they could have done was added ruler markings on the field camera bodies so you didn't have to carry one in the field, sometimes I wonder about these engineers... Lol
Maybe because it only works if the lenses used were made by the camera's manufacturer, and explicitly identified as working with the scale.
The idea about the ruler is good though.
Stone:
How would you deal with telephoto lens designs, or retro-focus lens designs?
The scale on the camera can only measure how far the lens board is from the film plane. The actual focal length of the lens is measured from the nodal point of the lens to the film plane (when focused at infinity) and with large format lenses, the distance between the nodal point and the lens board will vary with the design of the lens, its construction, and possibly the shutter used.
In many cases (telephotos, retro-focus design), the nodal point is actually effectively outside the physical body of the lens - it certainly isn't a consistent distance from the lens board.
Well I guess I've been measuring wrong... In any case, it can't be too far off from that? Within an inch? I don't even know what retro-focus means...
For some telephoto lenses, the nodal point is a long way forward of the front element and way outside the body of the lens.
And retro-focus construction is most often used for wide angle lenses. In that case it results in the nodal point also being outside the lens itself, except in this case it is behind the rear element. - some times a considerable distance behind.
Unless you know where those nodal points are, you cannot measure the distance between them and the film plane, and therefore cannot use single measurements from a fixed plane to determine an exposure calculation.
That is when the various tools that involve measuring magnification (e.g. using a ruler in the field of view) are most useful.
And that is why you can't build a scale on the camera for this purpose.
EDIT: for certainty and clarity, I mention that a "telephoto" lens is not the same as a long lens - it is a lens that is shorter than its focal length.
A bit of random googling yields an example of the Nikkor 1200mm f/18 lens which is focused at infinity when the bellows it is mounted on is extended to just 755 mm - about 450 mm or 18 inches less than the focal length of the lens.
The lenses you are using may not be strongly telephoto, or strongly retro-focus, in which case the nodal points may all be near the middle of the lenses.
But in any event, a scale on the camera wouldn't work.
Stone: Why do you need a chart for the RZ67? Wouldn't the built in exposure meter read less light as the bellows expands and automatically compensate for the final exposure?
Gotcha, okay that makes sense, but at least the ruler idea make sense still, however my question now is how the heck do I know what I have on my lenses that I own now, is there a marking point that I'm supposed to look for, I don't remember seeing any of those zeros with lines through them...
If your lenses are either telephotos or retro-focus designs, the "marking point" would be outside the body of the lens.
You need to use the other tools available for this purpose unless and until you determine where the nodal point is.
... a line through it showing that that is where the film plane is, so how can I know?
That is a problem. Information like that is available but one must read and understand the specification data for the lens in question. Knowing if your lens is a telephoto design or not is essential to knowing this.
I highly doubt any of my lenses are telephoto's, even if I bought a "telephoto", it wouldn't be a real one per your specification that the link has to be longer than the extension or something like that.
I own a 75mm f/4.5 grandagon, a 90mm f/9 Schneider super angulon and a 150mm f/5.6 Schneider super angulon, and I plan to purchase a fujinon 300mm f/8.5 C lens to complete my "kit" but the 300 is a compact lens so I don't think that qualifies as a telefoto in your new-to-me definition.
None of those are telephoto lenses. Measuring from the lensboard has always worked out well for me, as for the filmplane it's where the groundglass is.
Look on the side, or maybe even on both sides. Isn't there a blank scale that you can mark?
Wait I'm confused what other tools? The only tools available to me are my reciprocity timer, which asks me about the Bellas distance, however if the bells distance includes this extra space that is outside of the lens area, how can I tell where on the lens this point is? I don't see any special marking telling me where that point is like you do on a 35mm camera which has that zero with a line through it showing that that is where the film plane is, so how can I know?
By "other tools" I mean those tricks one can use with either a ruler or other standard item that you include in the scene, and then read the exposure adjustment off of the image on the ground glass.
Or you could use that fancy math you are trying to avoid
Believe it or not I'm actually still confused, I don't understand what helps me about putting the ruler into the scene, I'm just not following, ...
Post #15 and 22. I followed my own advise. Printing and gluing to a file card took about 1.78 minutes. Add another 5 for the Elmer's to dry. Send me your mailing address and it is yours. That plus about 3 minutes of playing with it will clarify everything in your mind.
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