Flocking Flock!

[Ari]

I bought some black flocking material from Dan here last week: https://www.photrio.com/forum/threads/light-trap-flocking-sheet-material.190820/#post-2532803
I'm sure I'll have more uses for it, but my immediate need was for a projector lens. It always looked hazy, but I wasn't sure if the glass was to blame, or if I had bad internal reflections.
So I bought Dan's stuff and once it arrived, I applied the black stuff to the inside of the lens, only in the part of the barrel that was straight, not the top flared section.
Here are the results:

Startling, to say the least. I was about a week away from trading this in for a bag of hockey pucks, the flocking saved this lens and made it into a real contender. The inside of the barrel is dark gray, and it's kind of shiny. Ergo, my hazy lens.

Here's a shot I took right after the work was done:

 

[AgX]

This is quite a difference!
But, how looked the barrel inside before then?

 

[Rick A]

Holy flock, what a difference.

 

[Dan Daniel]

Two very nice shots. The way the portrait goes out of focus is great.

The source for the material is here-

https://fpi-protostar.com/hitack.htm

They also have it on a sheet, no adhesive. This can be cut and rolled into a tube like a lens mount-

https://fpi-protostar.com/flockboard.htm

(To repeat the original post by me, I was buying some because I use as a light seal and such and was running out. My first use for it was on an older YashicaMat where it is known to reduce veiling from internal reflections; not as dramatic as these results but a definite improvement. I went ahead and order extra length of the 11 inch wide material since I was paying half in postage anyway, then I offered the surplus in a classified here at my cost plus postage. I am not in the business of supplying this, so contact the company if it looks interesting to you. And maybe buy some extra and do what I did here, just to get it around.) (And yes, since this always comes up, flat black paints can be used; if you know of a specific brand that gives a very flat true black, let us know!)

 

[Donald Qualls]

flat black paints can be used; if you know of a specific brand that gives a very flat true black, let us know!

I used Krylon Ultra Flat Black for the inside of my telescope tube (8" f/6.8 Newtonian/Dobsonian) when I built it in 1998. Haven't seen this paint in years, but it was pretty flat and pretty black as long as you didn't recoat.

 

[Ari]

This is quite a difference!
But, how looked the barrel inside before then?

Barrel was sort of reflective, a deep metal gray color.
The outside is quite glossy, and even the inside has a bit of a sheen to it.

 

[AgX]

Weird.
I have yet to come across a lens that not got its barrel blackened in some kind of way.

 

[Sirius Glass]

The flocked lens performs better than the deflocked lens, much as in the unrelated area of ministry.

 

[Helge]

A Kodak publication around the introduction of modern lens coatings, mentioned that light baffling, between the lens elements, was equally or more important then coating.

Trouble is, good baffling makes the lens barrel much wider and complex, which is contrary to what most camera makers wanted in the 50s and there after.

Flocking is probably a good compromise/alternative.

 

[mshchem]

This is a great demonstration of how a proper lens hood works as well. Multi-coated lenses, maybe not so dramatic, but still.

This is a great example.

 

[Dan Fromm]

Trouble is, good baffling makes the lens barrel much wider and complex, which is contrary to what most camera makers wanted in the 50s and there after.

Flocking is probably a good compromise/alternative.

Helge, flocking paper is probably the best solution for DIY. I've bought it from Edmund Indistrial Optics; I think that the source Dan Daniel suggested in post #4 above has better prices for small quantities.

But for killing glancing reflections from internal surfaces, fine grooves -- think filter threads -- are very effective. SKGrimes made several adapters for me that had severe internal reflections. I sent them back to be threaded, sorry, grooved, internally. The results were very good. I took the idea from a 300/4 TTH Telephoto ex-AGI F.139 aerial camera whose rear tube was threaded internally.

 

[Helge]

Helge, flocking paper is probably the best solution for DIY. I've bought it from Edmund Indistrial Optics; I think that the source Dan Daniel suggested in post #4 above has better prices for small quantities.
But for killing glancing reflections from internal surfaces, fine grooves -- think filter threads -- are very effective. SKGrimes made several adapters for me that had severe internal reflections. I sent them back to be threaded, sorry, grooved, internally. The results were very good. I took the idea from a 300/4 TTH Telephoto ex-AGI F.139 aerial camera whose rear tube was threaded internally.

Nothing is darker than the shade in a void. Only trouble is what creates the void will also create reflections.

 

[Dan Fromm]

Nothing is darker than the shade in a void. Only trouble is what creates the void will also create reflections.

Helge, I don't understand the point you're making. The TTH solution works, but it is not for DIY.

 

[Light Capture]

A Kodak publication around the introduction of modern lens coatings, mentioned that light baffling, between the lens elements, was equally or more important then coating.

Trouble is, good baffling makes the lens barrel much wider and complex, which is contrary to what most camera makers wanted in the 50s and there after.

Flocking is probably a good compromise/alternative.

+1 on this.
Remember reading some other manufacturers touted importance of internal reduction of reflections. For example late Hasselblad V system lenses had improved coatings inside the lens for reduction of internal reflections according to their marketing.
In this case, lens probably has very wide illumination circle that hits reflective area directly.
With most lenses built after 50's or 60's there was some measure to limit unnecessary illumination circles and reduce internal reflection either from edges of optical element or between the elements. This kind of mechanical vignetting improves contrast but affects bokeh and possibly some other properties.
Projection lens when used for projection has very limited illuminated area from the back side. For that reason it probably wouldn't need mechanical illumination circle limit when illuminated from the front side. Some lenses have square baffles on the rear side to illuminate only needed area and completely avoid illuminating camera internal surfaces and components.

 

[AgX]

Projection lens when used for projection has very limited illuminated area from the back side.

ALL the light going through the slide will pass through the rear of the lens barrel. Rear reflection off the lens elements will partially reach the rear of barrel surface.

 

[Light Capture]

ALL the light going through the slide will pass through the rear of the lens barrel. Rear reflection off the lens elements will partially reach the rear of barrel surface.

Correct. With old or damaged uncoated glass. These reflections from glass can be significant.

When used for imaging illumination light hits the sides directly hence the increase in flare when used that way.
A couple of Schneider's Cinelux lenses I have are shiny gold on the rear side and outside of the barrel. They come with properly blackened hoods on the front side.
Obviously, reflective area is either covered in projector mount or not important when used as projection lens.
When used for imaging, these areas should be flocked if they're causing flare. It doesn't affect every projection lens.

 

[Helge]

Helge, I don't understand the point you're making. The TTH solution works, but it is not for DIY.

No specific point. Just that even a black baffle will have some forward reflection.
No perfect solution.
Even a Vanta Black clone would not be good enough to totally eliminate diffuse reflection.

 

[Jeremy Mudd]

Fairly impressive difference! I ordered some of the flocking, hoping for similar results.

I have a 3D-Printed Dora Goodman Zone and I sprayed the inside of it with chalkboard paint to cut reflections, but its really not very flat black. The flocking should hopefully be much better.

Jeremy

 

[Chrismat]

I have used the same flocking material that Dan Daniel posted to flock the interior of Yashica tlrs. It may have something to do with age, but it seems on those cameras the interior seems to get lighter and makes them susceptible to flaring. Flocking them makes a big difference.

 

[Ari]

I used Krylon Ultra Flat Black for the inside of my telescope tube (8" f/6.8 Newtonian/Dobsonian) when I built it in 1998. Haven't seen this paint in years, but it was pretty flat and pretty black as long as you didn't recoat.

Couldn't find that locally, so I bought some Black 3.0 paint online to try on another lens, an experiment to see if I can pull more contrast out of an old brass lens.
I'm also very curious about this paint, and I have a few lenses that could benefit from a re-coating of the inside barrel.
I wonder if it's way too black? We'll see.
In case you haven't heard of this before:

 

[Donald Qualls]

For reflection reduction, there's no such thing as "too black".

 

[AgX]

Well, I expect "black as a hole" being unhealthy....