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Determining when to add flocking

 
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kpassaur



Joined: 24 Mar 2015
Posts: 22

PostPosted: Fri Dec 07, 2018 4:32 am    Post subject: Determining when to add flocking Reply with quote

How do you know when you need to add flocking?


I get the idea that light bounces around but what is the effect of it? Is it a grey overcast like when you need a lens hood on a reversed lens? Does it make highlights get easily blown out?

An example of a need for it would be great.

I'm using a bellows and from what I have read you only really need it on tubes and adapters. I read that if you use a cone with RMS threads you need to put it inside for sure - is that correct and how can you tell? Should you put all of your adapters together and then put a coat of black flocking paint?

Thanks in advance
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enricosavazzi



Joined: 21 Nov 2009
Posts: 1190
Location: Valdemarsvik, Sweden

PostPosted: Fri Dec 07, 2018 7:52 am    Post subject: Reply with quote

Some examples of symptoms that may suggest the need for flocking. Other members can no doubt extend this list.

- Low overall image contrast over the whole frame, and especially the lack of pure black areas. With modern lenses, the cause is almost always a need for flocking, but with old non-coated or single-coated lenses it may also be caused by a need to use a lens shade.
- A veiling glare or a lighter spot concentrated in the central portion of the image, without a sharp border. This one is frequently caused by a need for a lens shade (also with modern multicoated lenses), so in this case you should try first using a lens shade as narrow as possible and as long as possible, and if it does not solve the problem also add flocking.

If you see bright reflections anywhere from the tube/bellows/lens barrel interiors when looking through its rear with a lens mounted at its front, this also suggests a need for flocking.

Also keep in mind that light leaks through the lens mount, pinholes in the bellows material, or joints between extension tubes can cause similar effects but may need to be fixed in a different way.
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 20025
Location: Richland, Washington State, USA

PostPosted: Fri Dec 07, 2018 10:36 am    Post subject: Reply with quote

For some discussion & examples, see http://www.photomacrography.net/forum/viewtopic.php?t=35350 , especially image panel 4 in the posting.

--Rik
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Chris S.
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Joined: 05 Apr 2009
Posts: 3296
Location: Ohio, USA

PostPosted: Sat Dec 08, 2018 12:29 am    Post subject: Re: Determining when to add flocking Reply with quote

Solid answers already given, to which I'll add:

kpassaur wrote:
I'm using a bellows and from what I have read you only really need it on tubes and adapters. I read that if you use a cone with RMS threads you need to put it inside for sure - is that correct and how can you tell? Should you put all of your adapters together and then put a coat of black flocking paint?

A bellows is about the only thing in my macro rigs that I don't flock. The accordion-folds, in my experience, are ideal for avoiding reflection.

Cone adapters have a very strong need for flocking. Even a very good one I have--whose maker made a concerted effort to machine and internally treat it to avoid reflection--causes severe flaring without flocking material.

I wouldn't be quick to trust flocking paint for the work we do--especially at low angles, it's likely to be much more reflective than one of the "known good" fuzzy materials, such as Protostar or Doodlebug.

kpassaur wrote:
How do you know when you need to add flocking?

With the exception of the bellows, I flock every possible internal surface of my rigs. Flare and bright spots can be devilish to troubleshoot, and I've found it easier just to assume that everything that can be flocked should be flocked.

--Chris S.
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Yawns



Joined: 20 Dec 2015
Posts: 355
Location: Benavente, Portugal

PostPosted: Sat Dec 08, 2018 4:20 am    Post subject: Reply with quote

what about baffles?.. I use 3 baffles along the tube, one at start, another in the middle and another in the rear, in the belief (maybe naif) if the sensor cannot "see" the tube walls it will not be hit by the reflections... ...



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ChrisR
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Joined: 14 Mar 2009
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Location: Near London, UK

PostPosted: Sat Dec 08, 2018 6:16 am    Post subject: Reply with quote

I do that too, it seems to work pretty well - even just black craft paper. Ideally you need to get the aperture exactly the right shape, though.
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Chris S.
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PostPosted: Sun Dec 09, 2018 1:52 am    Post subject: Reply with quote

Yawns wrote:
what about baffles?

Agreed--baffles can also work very well in some situations. The accordion folds that work well in my bellows units are quite like a series of baffles. Also, a "flare-cut stop" placed near the sensor--often a valuable technique for reducing flare--might also be thought of as a kind of baffle.

All of these approaches--flocking, baffles, light-cut stops--can reduce flare, when correctly applied, in a macro or micro setup. Consequently, each deserves to be understood by anyone looking to build or improve a macro or micro setup.

Contrast reduction from internal reflection is a big problem in the photography of small things. This being the case, every bit of internal reflection you remove from your system will increase the contrast/general quality of your images.

--Chris S.
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Yawns



Joined: 20 Dec 2015
Posts: 355
Location: Benavente, Portugal

PostPosted: Sun Dec 09, 2018 10:20 am    Post subject: Reply with quote

ChrisR wrote:
I do that too, it seems to work pretty well - even just black craft paper. Ideally you need to get the aperture exactly the right shape, though.


Thank you ...
I am not getting what you mean ... do I have to keep it the same size (diameter) or the same "shape" (circle) .. or both Smile

I try a lot of things.. I'm not sure if they make a difference, but at least I tried...
Like covering the shiny metal of the objectives, and make hoods, when the WD allows for it .. what you see there is the AmScope 4X well wrapped and hooded..(to don't damage the barrels first I wrap it with kitchen film.. protects the barrel and the kitchen film glue is very weak ...

I also cover all the tube with a few turns of black wool flannel (before I was using the leg part of a pair of socks Smile ) and keep it in place with a few rings of elastic band I sewed.. once I was failing stack after stack and going very frustrated, until I found it was an helicoid leaking light .. I don't trust the tubes and adapter connections anymore.

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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Sun Dec 09, 2018 11:22 am    Post subject: Reply with quote

Yawns wrote:
ChrisR wrote:
I do that too, it seems to work pretty well - even just black craft paper. Ideally you need to get the aperture exactly the right shape, though.


Thank you ...
I am not getting what you mean ... do I have to keep it the same size (diameter) or the same "shape" (circle) .. or both Smile

See the diagram at http://www.photomacrography.net/forum/viewtopic.php?p=120423#120423 . If you're a glutton for punishment, you can also read the (long) discussion in the surrounding thread, which eventually led to the creation of that diagram.

Very briefly, the optimum shape for any baffle is the smallest hole that will just barely pass all the imaging rays. The optimum baffle shape is a rectangle with its corners modified to match the size and shape of the aperture, depending on placement along the optical axis.

In practice you can deviate quite a bit from the optimum shape and still get excellent control of reflections. The most important requirement is to block any single-bounce paths between aperture and sensor. That can be done with numerous baffles, say one per tube in a string of extension tubes, that have pretty large cylindrical holes but still prevent the sides of the tubes from being seen by both the aperture and the sensor.

--Rik
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