Industar 61 question (light baffle)

[Spyderman]

There's a removable round light baffle in the back of the lens. As I did a CLA to it, I had to remove the baffle. I'm just wondering if I should put it back, as it seems that it will block some light and cause light fall off at wide open apertures.

Has anyone here encountered a light fall off problem with this lens? and with the light baffle?

 

[Kim Coxon]

Hi,
The baffle is there to stop unwanted internal reflections. Some lenses have lost theirs as they are a push fit. They will not cause any light falloff and it is best to replace it.

Kim

 

[Spyderman]

I know what it's for 🙂

Anyone else have any recommendations or experience to share?

 

[pshinkaw]

I replaced mine when I cleaned and lubricated the lens. Having it in does not appear to have any bad effects.

-Paul

 

[Spyderman]

So I put it back in.

But still I was curious whether you were right. So I removed the back cover, openned the shutter at Bulb and looked from corner of the frame hrough the lens. Sure the baffle was an obstacle in the way! As looking from the corner of the frame, it obscured about 10 or 20 % of the area of the glass! Just try it yourself if you don't believe me.

So I removed the baffle for good.

 

[pshinkaw]

You don't think that the baffle was installed for a reason? The Soviets seldom put in things for frivolous reasons.

-Paul

 

[Jocko]

Today's new word: Hubris

Ian

 

[Kim Coxon]

If the light baffle was cutting down the light, then removing it will affect the exposure and you f stop markings will no longer be valid unless you use it on a later Leica, Bessa or other camera with TTL metering. Un fortunately, the test you applied does not show the true optical path. Put a frosted screen on the film plane and see if there is a difference in the image. I suspect not. A little while ago, I serviced a batch of about 10 I61's both black and Panda. In the subsequent test run done at full aperture, there was no difference in exposure between those with and those without the baffle.

If you feel better with it out, it will do no harm apart from the increased chance of flaring or ghosting.

Kim