Super Speed Graphic; Rangefinder Coincidence vs Perfect Focus Test

[Bart B]

Today's task with my just-acquired SSG was to check the focusing accuracy of rangefinder vs. ground glass image. I'd not yet made any critical focus tests; too busy learning about the flash and all its accessories so I can mount an old speedlight atop the Graflite tube and connect its PC cord to a suitable connecting point on the tube.

To begin with, both the fresnel field lens and ground glass were smudged with finger prints and some dust and/or lint was between these two parts. They're easily removed and cleaned with optic lens cleaner then dryed with lint-free lens cloth. Now they both look almost new. Both pieces went back in ensuring the fresnel lens grooves mated with the ground surface of the glass then installed with the field lens's smooth side towards the lens; ground glass smooth side towards the back.

With the lens all the way back at its stop, the rangefinder had good coincidence at infinity. I used a 10X loupe on the ground glass to get precice focus and had to move the lens forward about .030" or so for sharpest focus, then checked the rangefinder; 'twasn't coincident. At about 12 feet, the lens had to be moved forward about the same amount from rangefinder coincidence to sharpest focused image on the ground glass. Same thing at 4 feet. Maybe the stops got moved.

Does this mean the infinity stops need to be repositioned about .030" forward?

Bart

[rdenney]

We'll start with the assumption that the rangefinder is calibrated, and has the correct cam for your lens. We'll also assume that the focus scale is also the correct one for your lens.

Without worrying yet about the location of the lens standard, adjust the focus knob until the rangefinder indicates a subject at infinity is in focus. Then, lock the bed rail down.

Slide the loose lens standard along the locked bed rail until the ground glass shows that the infinity subject is in focus. Now, the ground glass and the rangefinder should be showing infinity focus at the same time. Adjust the pointer on the bed rail to point at infinity on the focus scale, if it isn't already. Note that the bed rail should be just extended out of the camera only a little bit--about 1/8" or so--when the rangefinder indicates a subject at infinity is in focus.

After doing all that, check that the lens and rangefinder correspond at closer distances. If they don't, check that the cam is the correct one for that lens. If it is, then rangefinder needs to be adjusted and I have to defer to others at that point. If everything looks good at this point, install the infinity stops at the current location of the standard.

This is the procedure I followed for setting the infinity stops on my top-rangefinder Pacemaker, and I'm reasonably sure it will work on a Super.

Rick "whose 127mm lens and cam were perfect after following that procedure" Denney

[BetterSense]

Note that the bed rail should be just extended out of the camera only a little bit--about 1/8" or so--when the rangefinder indicates a subject at infinity is in focus.

Why? On my pacemaker I set it up so that it hits infinity with the rail slammed all the way back. Easier that way.

[Bart B]

Note that the bed rail should be just extended out of the camera only a little bit--about 1/8" or so--when the rangefinder indicates a subject at infinity is in focus.

That doesn't make sense at all. I think a coincidence rangefinder focused camera should have a hard stop at each lens' infinity setting. Ain't that how manually focused great cameras of other makes are made? My old 2x3 Graflex I had back in the 1960's focused perfect with the rail's "slammed (gently)" all the way back. That's how the guy at the camera repair shop who sold it to me told me how it's used. Maybe I'm missing something; I'll appreciate any comments/info/reasoning to convince me otherwise.

Why? On my pacemaker I set it up so that it hits infinity with the rail slammed all the way back. Easier that way.

This is how I verified my Super Speed Graphic was properly set up for the rangefinder. Rangefinder coincidence happened with the rack all the way back gently.

I ended up using a .030" feeler gage to set the infinity stops that far forward from their original position. This made sharpest focus at infinity, 15 foot and 4 foot targets agree with rangefinder coincidence at those distances. So, the right cam must be in as well as the rangefinder calibrated decently. Things look pretty good to me, anyway.

If I can get a 20X loupe (or make one?) I'll check focus on the ground glass more precisly.

Bart

[Jack Dahlgren]

That doesn't make sense at all. I think a coincidence rangefinder focused camera should have a hard stop at each lens' infinity setting.
Bart

If you do that how are you ever going to focus beyond infinity?

Rick is wise to leave room to go further than man has been before.

[Bart B]

on my wanting to limit focusing to just at infinity:

"If you do that how are you ever going to focus beyond infinity?"

Well, after racking the lens back to its stop, how 'bout just takin' 3 or 4 steps towards infinity with the camera pointing at it? Then it'll be focused about 10 feet or so beyond infinity.

Bart

PS: Wink.

[rdenney]

Why? On my pacemaker I set it up so that it hits infinity with the rail slammed all the way back. Easier that way.

It's nice to have a little adjustment on both side of infinity to be able to account for thermal expansion, lens movements (which have a bit of slop in them on most well-used Graflexes), and gravitational attraction of the Moon.

And that's what Graflex apparently intended, too, based on the instructions I've seen for rangefinder calibration. But that doesn't mean, of course, that it must be that way. Do it however you want.

In practice, the only time a hard stop at infinity seems that important to me is in astrophotography and night photography. When I focus, I rock the focus control back and forth around the subject on the ground glass. That allows me to split the difference when it's hard to be sure of precise focus (such as at a small aperture). But, as I say, do it however you want.

Rick "recalling CZJ lenses from the 50's that focused slightly beyond infinity to allow for thermal expansion" Denney

[Bob Salomon]

Normally the ground side of the gg and the grooved side of the fresnel both face the lens, not each other.

[BrianShaw]

Normally the ground side of the gg and the grooved side of the fresnel both face the lens, not each other.

"Normally", but not on the Graphic.

[BrianShaw]

Normally the ground side of the gg and the grooved side of the fresnel both face the lens, not each other.

p.s. "normally" doesn't the fresnel go behind the gg (toward the back of the camera)? On the graphic the fresnel goes in front of the gg (toward the lens). Odd, eh? But true!