Stereo Pair Exposure

[Truzi]

Is it normal for one image in a stereo pair to appear a bit darker than the other? Is the small spacing between the lenses really enough to show a difference in illumination due to the (very slight) difference in angles?

I'd purchased a very nice Realist 45 on ebay. Despite it probably only ever having a few rolls through it, I did notice the right and left image appear to have a slight difference in EI (if I'm using the term correctly). Since the unit is from the 50s, I figured it would need a CLA anyway. The difference does not really cause any problems; it is not really noticeable when viewing the images correctly - but I know that doesn't mean anything.

Last week my best friend was given her grandfather's Corte-Scope (the earlier American Corte-Scope Company version). I noticed the same apparent issue on the cards that came with the Corte-Scope. Then I searched online, and noticed the same effect on many stereo pairs, both old and new. However, I could not find any information on this particular issue.

 

[John Koehrer]

It sounds reasonable that the exposure would be slightly different, I believe there are two separate shutters in the camera. A CLA should really help out.

FWIW, EI=exposure index, your personally tested/rated speed for a given film. I think you're looking for "density" to describe the difference in exposure.

 

[johnielvis]

it's not the shutter. The shutters in realists are linked mechanically so there's not going to be variation in the exposure between the shutters. However, even though the apertures are liked (by a belt), there IS some slop in those. one aperture will be slightly bigger or smaller depending on which one you rotate to change the size. You can easily clean the realist shutters yourself and tighten the screws if they're coming loose--they are a simple two-leaf shutter in each lens. the screws in the front allow the front plate to come off and voila the internal works.

 

[polyglot]

They should match, but may not if one shutter is running at a slightly wrong speed.

You might (rarely) get differences with a well-calibrated camera, e.g. different flare appearing in each lens because one is shaded and the other is not.

 

[GregW]

Haze and or fungus will cause this as well.
greg

 

[MattKing]

Haze and or fungus will cause this as well.
greg

Dirt, too.

 

[summicron1]

Jonieelvis and original poster-- the realist 45 is not like other stereo realist cameras, which were made in USA and have a single metal guillitine shutter and are fairly simple to service. The 45 is German-made, really an Iloca, with two separate blade shutters which are linked, but are not the same as what you describe. If one is a bit sticky and slow, it will definitely give you differing exposures.

Time for a CLA, although for the price you can probably find a more traditional Realist camera, the boxy-looking predecessor to the 45 which jonieelvis is thinking of. That camera will be more durable, have a built-in rangefinder with no parallax, and be funkier to use. The Realist 3.5 models in usable condition usually run $100 or so. Those with the 2.8 lens cost more, but are no better, image-wise, and for stereo you want smaller aperture anyway.

here's a good description of the basic models http://en.wikipedia.org/wiki/Stereo_Realist

 

[Truzi]

I was looking for the traditional Realist, but this was about $50. The bottom plate still has luster, and the paint on the little area inside that scrapes off when you unhinge the back is mostly there. I'm pretty sure someone bought it, used it a few times, then put it a closet.

I still want an original Realist, but figure it'd need a CLA too, and my car right now is milking me dry.

 

[johnielvis]

correct--the "boxier" realist is the one. They are built to last and last. The 3.5 lens seems to be the most stable over time and performs very well--recommended over the 2.8 lens for sturdiness, performance (more contrast some say) and price.