"Oil on blades"...

duhast · Apr 30, 2013

I see this sometimes on eBay ads for vintage lenses. In fact, I looked at my vintage Minolta MC Rokkor 35mm lens, and it's there.

1. What is the cause?

2. What is the remediation?

3. If not fixed, what is the fallout from the oil being there?

Derrel · Apr 30, 2013

My opinion, for what it's worth:

Oil on the blades is caused by excessive oil, migrating out and onto the "sweet spot" of the blades, where it's visible. MANY lenses never ever have an issue with this. SOMETIMES, on older lenses, the blades get shiny and worn, and 'some' vendors will mistake that sheen for oil.

On "some lenses", sitting the lens on its bottom rear cap can cause the oil to migrate back to where it belongs, allegedly; this was supposed to be the remedy for the early Nikkor 35mm f/2 AF lens; later production runs never did have the oil problem; many say Nikon switched oil formulations, to one that would not 'run'. Oil can be removed by a __competent__ technician. If you don;t know how to do it, don't even THINK about it. (I would trust a guy like say, compur or mitica101 or a few others here on TPF, to be able to disassemble a lens enought to clean the oil off, but moi?? NO WAY!)

On many vintage lenses, which are used on adapters on Canon d-slr or mirrorless cameras, oil really isn't that big an issue. If the oil is in large amounts, and it becomes sticky, it can cause very slow blade actuation...buuuuut, if the lens is used stopped down to working aperture, a slightly sticky diaphragm is not the end of the world....I MEAN HEY, my engine block has some oil on it...car still works...sure, I've slopped some excess oil and gotten it on the block top and such...no big deal...

Ysarex · Apr 30, 2013

The cause is migration of lubricant from the helical threads of the lens to the aperture blades.

The remediation is to completely remove the oil with a de-greasing chemical. Aperture blades have to be dry.

The fallout is that the blades will drag during the exposure and fail to reach the correct f/stop in time before the shutter opens. You set the camera to f/11 for example and, dampened by the oil, the blades only make it to f/6.3 by the time the shutter opens.

Joe

mishele · Apr 30, 2013

LOL :hug::

duhast · Apr 30, 2013

mishele said:
LOL :hug::

I can only assume that in the vid they are giving me complete disassemble and repair instructions for the Minolta MC Rokkor 35mm lens, but unfortunately I don't speak freaky deeky Dutch...or is it German? Is it possible for you to provide an accurate translation of the instructions?