Establishing and marking infinity stops?greenspun.com : LUSENET : Large format photography : One Thread
I have a couple of older press cameras and am starting to get an extra lens or two. I've checked around (Midwest Photo, etc) and have been unable to locate the proper infinity stops to fit the rail. Is there a typical manner that the rail/standard can be marked for infinity without moving the existing stops? And even more elementary, is there a standard method to determine where this should be? Am I asking too much to mark on the rail some sort of distance scale? I suppose all of the could be possible using the ground glass exclusively, but for a beginner, the things seems to help alot. Suggestions greatly appreciated.
-- Roger Rouch (email@example.com), August 01, 1999
hi Roger, as for setting the infinity stops, i just took my camera outside one night and focused on a street light a couple of blocks away, and then i screwed the stops down. but it seems to me for lenses of different focal lengths you would require different cams for each lens??? do you have a different cam for each focal length you have?
-- david clark (firstname.lastname@example.org), August 01, 1999.
Dave, Well...that's another problem. One of the cameras is a Busch Pressman and the other a Super Graphic (long story how I got two such similar cameras). I have figured a different cam for the Pressman beyond even asking and again unable to locate the correct cams for the Graphic. I haven't thought of this as being so big a problem, as I do much of my focusing off the ground glass. Though the distance scale on the two has been helpful in fading light. How did you permanently mark your infinity focus.
-- roger rouch (email@example.com), August 01, 1999.
Hi Roger, with regards to the infinity stops. When I got my speed graphic it was in pretty good condition, and I figure it was pretty much the factory set-up. It's a 4*5 with 127mm, and I assume everything is properly mated to sync with the range finder. But to check it, I took a screw driver and losened up the infinity stops on the rails and slid them out of the way (slide them to the front, and becareful not to lose them in the process). Then adjust the rails to where the indicator on the metering index matches up the two infinity symbols, the one on the rail and the one on the bed. Now, with the camera on your tripod, when it is good and dark out, focus the camera on a point of light far off in the distance (of course you do this with the ground glass), and you do this by sliding the front standards up and down the rail by hand. When the light is in focus, flip the lever and lock the front standards in place, and that place is infinity. Now slide those little stops up to the front of the standard, and then lock them in place. Assuming you have the right cam, and assuming that the range finder is properly adjusted, you are set. If the range finder is not adjusted, then you will have to go to the Graflex Society home page and look over their records. Good Luck, David.
-- david clark (firstname.lastname@example.org), August 01, 1999.
Thanks for your patience in explaining that. It will certainly help when I get ready to set up for infinity. Yet what I'm hoping to figure out is the occation when I'm in the field and have an extra lens ready to go on a lensboard and would like to swap out the lens then and there for a better perspective. I'd hate to move the infinity stops around like you described in that situation.
-- Roger Rouch (email@example.com), August 01, 1999.
hi Roger, the infinity stops (at least the ones on my speed graflex) are hinged, and for instance when i use a 240mm lens for portraits or whatever, I just reach down and fold the stops over, and then you can crank out the standards and extend the bellows. however for a lens with greater wide angle you wouldn't reach out to the stops, i wouldn't think? anyway, my stops just flip up or lay down depending on what you want to do with them, and this doesn't effect their anchor point for my main lens. best regards, David
-- david clark (firstname.lastname@example.org), August 02, 1999.
This is sort of how I had pictured things going and is actually what I've done a few times. It would seem convenient to have a point of reference for infintity with the second lens that might be a spot of white-out or something on the rails to match up with the front of the standard. Perhaps it would be possible also to tape a small distance scale next to the rail that would indicate where the standard should be positioned based on some predetermined testing with the second lens and help with DOF? This could make up for my lack of appropriate cam to a degree. Or maybe I'm trying to oversimplify this based on my inexperience, and it will all come with more practice.
-- roger rouch (email@example.com), August 02, 1999.
Maybe I'm missing something here BUT I think this is fairly simple.
I'm basically a newbie who has a Crown Graphic that came with a 135mm lens and those flip metal infinity stops. With the 135m lens pulled to the stops, I measured from the film plane to the lens and noticed that it was ... 135mm. Rather obvious in retrospect, I believe.
So, when I buy new lenses, I pop them in their lensboard, pop them in the Crown Graphic, pull it out to the focal length, and make a black laundry-pen mark on the rails on both sides. Then when I change lenses, I merely unlock the bed, push/pull the bellows/standard out to the proper black lines and flip the lock to lock it in. It may not be perfect because I didn't spend an inordinate time looking for exactness, but it's pretty close. It can be as close as you want to spend the time for in being meticulous.
However, in answer to the original posted question: it seems that the infinity stops would be located so that, when the bed is pulled out to them and locked, the lens is the focal length away from the film plane.
Caveat 1: Without the Crown Graphic/ Pacemaker Graphic cams, the rangefinder won't work. The method I've described works fine if you will be using ground glass focussing.
Caveat 2: If you are doing this for a tele-photo (true telephoto by construction) lens, you would need to use the flange local distance instead of the focal length.
-- Richard Rankin (firstname.lastname@example.org), August 03, 1999.
I did the same as Richard, use the black marker, fine point, and then when you change focal lengths, just move the front standard to the appropreiate mark. Almost a no brainer. Pat
-- pat j. krentz (email@example.com), August 03, 1999.
As simple as it seems, that helps very much and now I know what to do. Thank you. I would suppose even simpler might be to verify the infinity stops of the first lens, and for subsequent lenses, rather than measure the distance from the film plane to the lens, measure the difference between the first lens infinity and the second on the rail as the difference of the two focal lengths.
-- Roger Rouch (firstname.lastname@example.org), August 04, 1999.
First, you can purchase used hinged infinity stops for the Graphic from Clayton Camera (they advertise in "Shutterbug")in St. Lous. You can use a mark on the focusing rail and save the cost of the stops but I kind of like being able to raise the hinges on the stops and zip the lens out to the stops, rather than having to try to eyeball the front of the lens and get it perfectly aligned with a pencil mark on the focusing rail. Many people do, however, use a pencil or some other kind of mark and it works fine if it is properly located on the focusing rail. Which leads to the next point concerning the location of the infinity stop or pencil mark. If you want to get it really right (as opposed to being in the very general ball park) it isn't overly difficult but it's also not necessarily simple. With respect to measuring from the film plane to "the lens," the problem is determining where on "the lens" you measure to. Focal lengths are determined by measuring to the nodal point of the lens. The nodal point is usually somewhere in the general vicinity of the center of the lens (except on telephoto lenses) but I don't know how you would go about finding it and measuring from it even if you could find it, though maybe there's some way of doing this that I don't know about. Secondly, lenses are seldom in fact the exact focal length as they are quoted. Manufacturers typically round their numbers. Thus a 150 mm lens (for example) is most likely really 148 mms or 152 mms when properly measured, not really 150 mms. For these reasons I personally wouldn't try to determine the infinity setting by measuring a distance equal to the quoted focal length from the film plane to "the lens." A better (IMHO) way is by looking at the ground glass but I think you need to focus on something farther away than a couple blocks. Infinity is a good bit farther than that. The recommendation that I've seen several times is something a mile away. Unless you live in the wide open spaces, finding an unobstructed view of something large enough to focus on that is a mile away isn't easy (or at least it wasn't for me). If you were going to use the rangefinder, and so needed cams and infinity stops and wanted to everything absolutely right, I think the thing to do would be to find a camera repair facility that has the necessary equipment to do it right. Marflex, the Linhof repair facility here in the United States, will place cams and infinity stops on Linhof cameras and there presumably are other repair facilities that can do this for other cameras. However, if you're not going to use the rangefinder I think the ground glass method should be sufficiently accurate for your purposes, if you can find something that is far enough away and large enough to focus on.
-- Brian Ellis (email@example.com), August 05, 1999.
If your rangefinder is accurate using the lens you now own, all you need to do is establish distance scales for the new lenses. Focus thru the ground glass while moving the unlocked front standard back and forth. Establish a point for infinity, make matching pencil marks on the bed and the moving rail. Focus at 15 feet, by moving the unlocked front standard again. Put another mark on the bed matching the rail mark. Do this again at 6 feet. You will then have three marks on the bed and one mark on the rail. Matching the rail mark with any of the other three will set the focus at that distance. In practice, focus using the rangfinder, look at the distance scale, note the distance, if it is 15 feet, turn you focus knob out until the pencil mark on the rail lines up with the bed mark for 15 feet. You will be focussed at 15 feet. If you could find them, you could actually install a set of Graflex distance scales for each lens you own, yet never actually change the adjustment of the rangefinder. Each time you focus, you would note the distance on the scale, then transfer this setting to the other distance scales.
-- Bill Moore (firstname.lastname@example.org), August 07, 1999.
The only point to be aware of is that Graphic front standards tend to have a bit of slop when not locked down. That is, you can end up with a bit of swing if not careful. I mark one side of the rail with a pen or pencil, then use a nice plastic drafting square to locate the other side. You can line it up along the edge of the one rail to make sure it's square. This works better than relying on the standard to lock down square to establish the marks, since it probably won't be true. If you always stop way down it won't matter anyway.
-- Chris (email@example.com), August 08, 1999.