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lens hoods for mitutoyo objectives?
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nathanm



Joined: 02 Jun 2016
Posts: 222
Location: Bellevue, WA

PostPosted: Fri Jul 29, 2016 12:37 pm    Post subject: lens hoods for mitutoyo objectives? Reply with quote

I have been at war with stray light recently, both inside my macro set ups, and with respect to lens hoods. A thread by elf on using a 3D printer to make lens hoods inspired me because it is perfect for the job.

The mitutoyo objectives I use have large front elements, and those elements are frequently able to "see" the light sources I use. So it stands to reason that they are getting stray light. Of course they will have some internal baffling, but in normal microscopy usage there may not be as much diffuse light sources. Stray light just can't do you any good, so if it is easy to block then why no do it?

Working distance is usually precious, but with 34-35mm for the 5X and 7.5X, and 33.5 mm for the 10X, there seems to be some room to have a hood.

An alternative of course is to put snoots on my light sources, but it may be easier to make a hood than do that.

In a few cases I have made a temporary hood with black gaffer's tape, but now I am thinking that I should make a 3D printed hood.

Does anybody have experience doing this?
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nathanm
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Saul



Joined: 31 Jan 2011
Posts: 1510
Location: Naperville, IL USA

PostPosted: Fri Jul 29, 2016 1:16 pm    Post subject: Reply with quote

Tried this:





Inside is:
http://www.photomacrography.net/forum/viewtopic.php?t=17917&highlight=black+doodlebug

Front - tin (foil) tape

Because I do not have problem with stray light with all Mitu's on my setup, did not go for 3D printing. It was just for testing ...
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Saul
Studio, horizontal and field setups
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genera



Joined: 05 Oct 2011
Posts: 117
Location: California, USA

PostPosted: Sat Jul 30, 2016 9:03 am    Post subject: Reply with quote

Here are a few I've made from heat shrink tubing.



They all started as white, approx. 2" diameter heat shrink. The black areas were dunked in paint after forming. The shorter one also has a protostar lining. The center hood is made in two pieces and can be expanded lengthwise.

This particular material was shrunk in boiling water over a cylindrical form of appropriate size. The size of the opening can be controlled to some extent, by controlling the amount of tubing that overhangs the form. If you let too much material overhang the end will curve down to the tube's minimum diameter. You can cut the overhang at an appropriate length / aperture. If you do it that way you'll end up with a hood shaped like the one on the right.

Sorry, I don't have a part number or manufacturer.
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-Gene
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ChrisR
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Joined: 14 Mar 2009
Posts: 8467
Location: Near London, UK

PostPosted: Sat Jul 30, 2016 1:08 pm    Post subject: Reply with quote

An old pic.
Alumin(i)um air-con duct tape is easy to form. Here lined with black paper, easy because the tape is sticky.


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Chris R
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elf



Joined: 18 Nov 2007
Posts: 1386

PostPosted: Sun Jul 31, 2016 2:49 pm    Post subject: Reply with quote

Check your PM.
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nathanm



Joined: 02 Jun 2016
Posts: 222
Location: Bellevue, WA

PostPosted: Fri Aug 26, 2016 7:06 pm    Post subject: Reply with quote

Here are the lens hoods I made for the Mitutoyo objectives.... so far they seem to work very well....

From left to right, hoods for the 5X, 7.5X, 10X and 20X.



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nathanm
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Fri Aug 26, 2016 10:50 pm    Post subject: Reply with quote

Looks good.

Two questions:

1) How large a sensor size are these designed for?

2) Where do the ends of these hoods end up, with respect to the focus subject plane?

--Rik
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Sat Aug 27, 2016 6:42 am    Post subject: Reply with quote

These are for full frame Canon. The working distance for the 5, 7.5 and 10x are all around 33-34 mm, the hoods are much smaller - like 12 mm past the end of the objective so there is still room to light. I will send a photo of them in action.
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nathanm
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Lou Jost



Joined: 04 Sep 2015
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PostPosted: Sat Aug 27, 2016 8:37 pm    Post subject: Reply with quote

I'm a little surprised the 10x one isn't more conical (tapered to a narrower entrance than exit).
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Lou Jost
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Sat Aug 27, 2016 9:49 pm    Post subject: Reply with quote

I tried to be conservative about the lens hood to avoid vignetting.

These hoods assume that one needs to "see" all of the front element from the frame. So the shape of the baffles is a simple linear interpolation between the front element and the frame. So it is equal to the frame at the working distance, and equal to the round front element at the objective end.

In reality if I knew where the entrance pupil is with more precision I might be able to make a tighter hood. There is a separate thread on how to find the entrance pupil on Mitutoyo objectives, but I made these hoods before the latest posts.

The main issue for a the hood is that when I use a large diffuse light source there is bound to be stray light, and the hood ought to help.

Mitutoyo engineers probably optimized for typical microscope lighting situations but we photographers tend to do use many other lighting modes
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nathanm
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jnh



Joined: 27 Apr 2015
Posts: 95
Location: US East Coast

PostPosted: Sun Aug 28, 2016 6:33 am    Post subject: Reply with quote

Quote:
Here are the lens hoods I made for the Mitutoyo objectives.... so far they seem to work very well....

Looks like, these are 3D printed. Would you be willing to share the design files?
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nathanm



Joined: 02 Jun 2016
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Location: Bellevue, WA

PostPosted: Sun Aug 28, 2016 7:12 am    Post subject: Reply with quote

happy to share ... but let me test them a bit more before I share them. I've learned to live with my errors but its embarrassing to push them on others...
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nathanm
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Lou Jost



Joined: 04 Sep 2015
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PostPosted: Sun Aug 28, 2016 7:25 am    Post subject: Reply with quote

Better yet, would you be interested in selling them? Those of us without 3-D printers are jealous!
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jnh



Joined: 27 Apr 2015
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PostPosted: Sun Aug 28, 2016 7:32 am    Post subject: Reply with quote

Thanks, much appreciated!
I just recently learned that my local library has a 3D printer, and I've been itching to try it out. That'll be a good learning experience - including errors...
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Beatsy



Joined: 05 Jul 2013
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PostPosted: Sun Aug 28, 2016 8:22 am    Post subject: Reply with quote

Lou Jost wrote:
Better yet, would you be interested in selling them? Those of us without 3-D printers are jealous!


Seconded!
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