[Mothballs]

Well, here we are. I was reading up on digital optimization of lenses, and came to a very simple observation of some Film era lenses vs their Digitally optimized counterparts, and I decided to experiment with adding a baffle to the backside of my Auto-Takumar 135mm to see if cutting down the light coming out the backside would increase contrast.

Out comes some craft foam and the exacto knife, and in it goes, far from the lens elements; The goal is to shrink the image circle, not act as an iris.

My results are... Inconclusive, and I'm uncertain if this is just forcing it down a stop, but I think there might be something to be had here: Have a look yourself. Images are just in camera JPGs, but I think There's a little bit of gain... Might just be confirmation bias though.

No baffle:

@1/80



@1/60


Baffle:

@1/60

---

Last edited by Mothballs; 09-25-2015 at 12:44 PM.

[marcusBMG]

Check out this thread on this topic and note the link to Christophe Esperado's web pages.

Legacy lens baffle size - Fourthirdsphoto Forum

PS always helpful to have an explanatory thread title ... like "OK so whats the effect of a DIY baffle on contrast ???

[Na Horuk]

Inconclusive, and I'm uncertain if this is just forcing it down a stop

To test this, take a photo of a measuring tape and try seeing whether the DoF changes. If DoF changes, then you are stopping down. If DoF is the same, but contrast is better, then the baffle is working as it should. And put a light source in the back, like a candle. Stopping down would affect the appearance of the light, as well (the OoF blur would be smaller, possibly with different shape/starburst). I'm recommending this kind of test, as its a bit difficult to see from the natural subjects in the sample photos. Just the metering of shutter speed might not be enough
Interesting thread, though.

[reh321]

Well, here we are. I was reading up on digital optimization of lenses, and came to a very simple observation of some Film era lenses vs their Digitally optimized counterparts, and I decided to experiment with adding a baffle to the backside of my Auto-Takumar 135mm to see if cutting down the light coming out the backside would increase contrast.

Out comes some craft foam and the exacto knife, and in it goes, far from the lens elements; The goal is to shrink the image circle, not act as an iris.

My results are... Inconclusive, and I'm uncertain if this is just forcing it down a stop, but I think there might be something to be had here: Have a look yourself. Images are just in camera JPGs, but I think There's a little bit of gain... Might just be confirmation bias though.

My experience, having tried just about every legacy lens in our house (which meant buying similar adapters for FD-mount, EF-mount, and K-mount) is that the big issue with film-era lenses is CA, and unfortunately, to my knowledge there is no way of dealing with that (and it damages sharpness even when you don't see purple or green fringing).