Zeiss-Opton 35mm f2.8 Biogon for Contax IIa/IIIa

[akkyuen]

Hi. I have an old Zeiss-Opton 35mm f2.8 Biogon for Contax IIa/IIIa. When I use this lens to take photo, there is always flare appeared at the central of the photo even I use an appropriate hood. May I know the reason? Thanks!

 

[Highway 61]

Hi, I think that there are oily deposits on the optical element located behind the aperture blades. This is common on old lenses.

Your lens need a CLA, which is normal as well, given that it's been made sixty years ago.

Open the diaphragm, then look at your lens through the rear while heading a flashlight beam in it through the front.

Chances are, that you'll notice a lot of haze in the rear group.

 

[sevo]

It looks like a light leak. But haze on concave elements can cause almost similar ("hot-spot") phenomena. Usually haze occurs in lenses, leaks in bodies, so it ought to be haze. However Biogon style designs are popular among the IR crowd for having a almost hot-spot free geometry, and other haze types would be either all over the image or symmetrical to the light source (i.e. in your example mirror the sky on top on the bottom half) - so that assumption is less likely to be true here than on the average SLR retrofocal.

Can you shoot a series of five test images of a dark surface with a point light source (torch or bare bulb) once centered, once on each corner, plus an extra image with lens cap on and the camera in bright light? That should settle it.

Oh, and first of all look into the lens to see whether the aperture leaves are in a jumble - that would be another pretty obvious cause of similar phenomena...

 

[akkyuen]

Thanks for your kind reply. I examine the lens under a strong light source and find there is a large grey circle at the center of the internal glasses. I think this is the reason causing the problem. Is it haze or separation?

 

[BobYIL]

Thanks for your kind reply. I examine the lens under a strong light source and find there is a large grey circle at the center of the internal glasses. I think this is the reason causing the problem. Is it haze or separation?

Haze.. your lens is from the natural-oils era, i.e. evaporating oils, for the diaphragm blades usually whale oil (used also for margarine 😀 ). Sometimes this appears as a uniform haze to cover a lens surface, sometimes as a central round spot light grayish tone, sometimes as a thick fat ring. Today synthetic oils are used and despite of it lens haze has not been eliminated totally.

Have a pen-light or flashlight with adjustable beam? Point it in, you will see the haze spot.

 

[Highway 61]

Thanks for your kind reply. I examine the lens under a strong light source and find there is a large grey circle at the center of the internal glasses. I think this is the reason causing the problem. Is it haze or separation?

This is haze and as written above once cleaned up the lens will perform perfectly.