There is a horrible feeling. The horrible feeling occurs about the time you get some pictures back from your new, (or new to you) old camera, and you notice that they just aren't sharp. As your friends tell you that you should have been using your digital, because you can preview and see right there on your little screen if the camera is right... blah blah.. Your heart sinks.
The truth is, almost every old camera has a super sharp lens, almost unbelievably so by today's standards, but it may be out of calibration. The mirror in your SLR might not be quite right, making the focus setting you see different from what the actual film will see. In a rangefinder, the little window might not be in the right place, making you set focus incorrectly in all your shots. The problems become really noticeable with fast lenses and close distances.
There is no excuse for all this mess because you can check the calibration to intense accuracy with just a few things, and cheap things at that. September of last year, I reposted my article about making a ghetto DIY autocollimator, a device for looking in the camera and seeing if it is focusing right.
http://photocontraptions.blogspot.com/2009/09/ghetto-auto-collimator-explanified.html
But that's a bit of work, and ridiculous work. So, for just checking focus, we can do nicely on the SUPER cheap with an easier method. It only takes minutes. If your camera is good you will know for sure. If not, you can find a technician, or in some cases calibrate the camera yourself. We'll get to resetting bad cameras soon, but for now, let's get started checking focus calibration on your camera.
First, you need your camera in question, of course. I am going to demonstrate this procedure with a crusty Argus Brick rangefinder, and a 35mm SLR camera as well. You'll see that the process is pretty much the same with anything.
Meet the test candidates.
So you need a few things: First off, some frosty tape.
Tape. Frosty goodness.
Gotta have it. Then a marker that can mark on... tape.
...a decent pen. Sharpie or something...
Then, a locking cable release. We have to hold the camera open so we can see what is going on in there. It should have a way to lock open, so you don't have to get your little brother to stand there all day.
locking cable release that fits your camera
Shame on you if you don't have one. Anyway, you need some sort of light source. A flashlight will do nicely, or any bare lightbulb you can position behind the camera. You'll see what I mean in a second.
flashlight... or something
Now the final ingredient. This is the tough one. You need a "viewing device," which can be any old SLR camera with a lens that is magnitudes longer than the one you are testing. Lens quality is of literally NO concern, but the camera should probably have a real glass prism, not the pentamirror/brightscreen nonsense on most modern plastic SLRs and DSLRs. All older SLRs have a real prism and a real viewing groundglass, but only the more expensive new cameras do now. This explains why it is so easy to manually focus an older camera than say, a Nikon D50 or Canon EOS Rebel. For our test, we shall use this trusty Minolta SRT from the 60s.
If you don't have something like this goofy example, find somebody with a lens at least two or three times as long as the lens you are testing and borrow that.
For example: The cameras we are testing are both using 50mm lenses, (Argus Cintar 50mm f/3.5, and SMC Pentax-A 1:1.7 50mm.) So a 200mm lens would suffice. The miserable 300mm f/5.5 here is fabulous for the task.
The "viewing" camera will be like an eyepiece for us, so we have to have things right with that viewfinder first. We just have to make sure it looks focused to infinity, or really, really far away. Go outside with this contraption and focus on an object as far away as you can. Use something like a lamp post way down the street, or some small detail hundreds or thousands of feet away. If the lens turns out to be set to infinity, great. If not, whatever. Just keep it where it is from now on. Ready to go!
Now let's get the cameras ready for the test.
Open up your camera and take a look inside. The film passes over a pair of rails, and is held tight against them by the pressure plate on the back door. Here you can see the rails at the top and bottom of the frame.
Exhibit A: On the Argus... There they are!
Tape
Attach a chunk of tape to the top rail, and bring it down...
To the other one. I know. pretty obvious.
You might have to press on the edges like shown to get a nice flat tension on our new focusing screen. It has to be stretched totally flat.
Then the marker...
Make a nice target, just to make it totally clear what we are looking at. Probably not necessary, but It does help.
Ready!
Should wind up looking like this. This one is ready to go.
With the SLR, the shutter is way at the back of the camera, so we have to be extremely careful. It is never a good idea to touch a shutter of any type. If you don't manage to break the shutter, the oils from your finger can interfere with the blades. Try to keep this in mind, or set the camera to "B" (long exposure) and use the cable release to lock the shutter open. If you do it that way, make sure the release is secure. You certainly don't want your mits up in there and have the shutter try to slam on your finger. I'll just show you with the shutter closed, just to be macho.
A little more treacherous with the SLR.
As you can see, somebody already got their crummy fingers on this shutter anyway. Oh well.
Applied to top rail.
Now, the bottom.
installed.
... and the X. Be careful!
Whew.
Now set the camera to "B" and lock the camera open with the cable release, and figure out a way to get it sitting on a table, facing forward.
...cable release added to the Argus and set to "B."
Now, grab the flashlight, and get it aimed at our calibration tape as shown.
Lamp positioned with magical blue found object.
Make sure to focus the test camera lens to what the camera says is infinity, and set the lens wide open. Hopefully it will be correct.
Looks good. Rather bright in there.
I'll show you with the SLR too.
Wow. Dirty.
Now we just look in there with the "viewing lens." It's that simple. Position the viewing camera to be facing straight into the test one, and look inside. Since both lenses are focused to infinity, it doesn't matter how far they are away from each other, so get them nice and close.
Here is how it should look when you are testing.
The image (the tape with X,) will come out of the test camera as if from infinitely far away, and be refocused to the viewing camera ground glass that you calibrated to the really far away things. If everything is good, you will see a sharp image of the "X" and the tape in the viewfinder of the other camera. Being that the viewing lens is magnitudes longer, the crop will show you only a small part of the tape. This is vaguely like looking really closely to a picture with a magnifying glass. With this much magnification, it will be TOTALLY OBVIOUS to you if the camera is out of calibration. It should snap into sharp focus just as the test camera focus reaches the infinity setting, and go really blurry as you change focus of the test camera.
Trying it out.
Here is how it looks:
Hopefully like this.
...Not like this.
See? Easy. This has been a lifesaver with old folding cameras, with their complicated bellows systems, weird lens mount adapters, helicals, cheap stuff like Holgas, Impreials, beat up rangefinders and especially setting the infinity stops on field and press cameras that don't have their own ground glass. Try it! Feels good knowing that blurry pictures are totally your own fault.
Next episode we can learn how easy it is to recalibrate a rangefinder, or make a high performance groundglass of our own. ... or make a whole camera from scratch... or not. Who knows. Let me know.
Oh, and the test cameras? Turns out the Argus is working perfectly and the SLR is not right at all!
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