Seeking high quality optical flocking for lens adapters

[dheck]

I have a Sony A7II and a variety of lenses in other mounts and their respective adapters. I've noticed some serious loss of contrast from some of the faster lenses when wide open which I am wondering may be at least partly due to flare and internal reflections in the adapters.

I'd like to try adding some flocking to the adapters and test for improvement. There seem to be a number of far-flung suppliers on ebay and at optical / astronomy suppliers in the US but I haven't found anywhere in Australia. Self-adhesive felt / velour is available at Bunnings and other hardware stores but I suspect that (at least some of) the special purpose material would work better.

Does anyone have any tips about obtaining adhesive flocking or the relative quality of different sources?

*removed - refer to the site rules, in particular rules 3 and 4*

Thanks, darkly!
Daniel

[jjphoto]

Can you get matte black tape (like masking tape) to test your theory that flare is the issue. I use tape that I get from John Barry (cine equipment supplier).

http://www.johnbarry.com.au/photogra...black-mas-1blk

I've been using this stuff for the exact same reason you are after flocking and find it works well. Being tape, it doesn't have any loose material than can end up on the sensor.

[dheck]

Apologies for posting the link as a new member.

And thanks John -- that's a good suggestion and thanks for providing your experience.

Cheers,
Daniel

[ameerat42]

Daniel. Think about how light enters a lens. Rays from spurious angles don't usually make it straight to the sensor to form the image,
but they might end up there after a bit of bouncing around inside the lens.

So, are you sure it is the adapters that are the cause? It could be that the lenses need a (good) lens hood.

Anyway, just a stRay thought.

(Darkly! - Ha-ha-ha!)

Am.

[dheck]

Thanks Am.

The most problematic lens / adapter combination is actually the highly regarded Tamron SP 90mm f2.5 on the A7II... it's really hazy at f2.5. Nobody else seems to have this problem so I suspect that the combination of a flat rear element and a highly reflective digital sensor in a long somewhat shiny (black anodized) mount adapter is particularly problematic. I have tested in controlled lighting, with the original hood and that doesn't fix the problem.

The real clincher was when I tried the same lens on my A mount body which has a much shorter adapter tube. That combination showed much less contrast loss at the larger apertures.

It will be an easy test to tape, flock or even paint the inside of the E mount adapter and see if that helps.

Cheers!
Daniel

[ameerat42]

Sounds like you've done the homework. I can't help with any flocking supplies. When I had a similar problem
decades past with a telescope even flat black paint wasn't flat enough and I had to add some baffles in the
tube. I hope yours is easier to solve

- - - Updated - - -

PS: Even if you manage to reduce it some, you may have to resort to some PP tonal adjustment for
pics with that combo.

[nardes]

Have a look at this US website at their "flocking" material for telescopes.

http://www.fpi-protostar.com/flock.htm

The Bunnings stuff “may”? shed fibres whereas the Protostar stuff apparently does not.

Cheers

Dennis

[dheck]

Hi Dennis,

Yes -- that stuff has good reports for this application.

That was the link that was removed from my original post, in fact (as a new member, I can't post commercial links). I'm waiting for a reply from them to my shipping cost enquiry (made 2 days ago)...

I was hoping there may be somewhere closer where I could obtain smaller quantities more quickly and cheaply, though.

Cheers,
Daniel

[jjphoto]

Thanks Am.

The most problematic lens / adapter combination is actually the highly regarded Tamron SP 90mm f2.5 on the A7II... it's really hazy at f2.5. Nobody else seems to have this problem so I suspect that the combination of a flat rear element and a highly reflective digital sensor in a long somewhat shiny (black anodized) mount adapter is particularly problematic. I have tested in controlled lighting, with the original hood and that doesn't fix the problem.

The real clincher was when I tried the same lens on my A mount body which has a much shorter adapter tube. That combination showed much less contrast loss at the larger apertures.

It will be an easy test to tape, flock or even paint the inside of the E mount adapter and see if that helps.

Cheers!
Daniel

Correct me if I'm wrong but doesn't that lens have an issue with a hot spot (Google it)? A flare spot is essentially a form of flare and depending on the aperture and magnification it can either appear as haze or a light spot in the shape of the aperture in the centre of an image.

An example of a flare spot. The spot is visible at F8 but is just haze at F2.8.


Are you having flare issues with other lenses using the same adapter or only/mainly with the Tamron? Maybe the lens is the issue as much as the adapter itself, which is not to say you shouldn't try to improve the adapter.

[dheck]

Thanks John,

You're right about that lens and its hotspot issues. That's actually the reason I thought it might be particularly prone to adapter internal reflection as well... I'm seeing the problem even in moderate lighting conditions whereas the hotspot afaik seems to require a very bright lightsource in or near the field-of-view.

Most lenses have reduced contrast wide open, of course, so I've certainly observed it with many of my other adpated lenses to lesser degrees. Honestly don't know to what extent that may be exacerbated by lens adapters, but I'm curious to find out!

I'll try something on the weekend and see how it goes!

Cheers,
Daniel