Horizontal stripes - along same depth, like ISO lines...

Starting point for beginners questions.
jrburns47
Posts: 165
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Horizontal stripes - along same depth, like ISO lines...

Post by jrburns47 »

Set up a card to block laser light so that some of the laser light falls onto a white card downstream. Sometimes i’ve noticed a series of black lines on the white card matching the edge of the blocking black card, i.e., edge diffraction. BobH is an excellent holographer and card blocking obviously works well for him. I use black blocking cards extensively but always keep an eye out for unwanted edge diffraction. The 3M 235 black tape i previously described comes in different widths and is generally useful to have around a holo lab/studio in my opinion, in addition to the plate/film edge blocking I mentioned. I don’t own stock in 3M 🤪😊😷.
BobH
Posts: 440
Joined: Tue Jan 06, 2015 10:26 pm
Location: Mesa, AZ

Re: Horizontal stripes - along same depth, like ISO lines...

Post by BobH »

My favorite tape too, and a "must have" for any hololab. You're right about edge "ringing" from cards used to mask edges, but if they are only a few inches away, the issue is minimized. Also, I'd worry about tape touching photopolymer that's only very lightly attached to the glass. If one uses ink on the top edge, the line across the scene in a Denisyuk setup is minimized. An edge mask for the bottom edge seems like the easiest to do. All will work. Best is what's available and easiest for the holographer.
jrburns47
Posts: 165
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Horizontal stripes - along same depth, like ISO lines...

Post by jrburns47 »

Interesting point re photopolymer. I’ve only made a few tests with it and hadn’t considered the edge diffraction issue with it yet. I’ve been mostly using silver halide glass plates for which the 235 tape is useful. i’ve been gearing up for more extensive HX200 work and worked out a homebrew laminar flow hood and gotten the 1watt yellow safelights and even had a 4x8ftx3/16” glass sheet of Starfire glass cut up for use as substrates but haven’t bitten the bullet to spend the $ necessary to get a roll of material.
SarahC
Posts: 7
Joined: Sat Oct 17, 2020 2:53 am

Re: Horizontal stripes - along same depth, like ISO lines...

Post by SarahC »

I'm just in the process of talking to Tatjana to get an 18 sheet pack of 10 x 15cm Bayfol HX200... currently at ~£100.

Oh no........ I've got a rainbow of colours for safe lights, from super deep cherry red luxor, through to near UV-A, but not yellow. =(

Any torches on Amazon UK have the right frequency yellow would anyone recommend?

My dark room is the kitchen at 3am - I'm THAT dedicated I get up early rather than change the bulb in the shed.
jrburns47
Posts: 165
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Horizontal stripes - along same depth, like ISO lines...

Post by jrburns47 »

Westinghouse Lighting 03465 Nanolux 1-Watt G19 LED Bulb, Amber https://www.amazon.com/dp/B000UQ0HO8/re ... JFb3YBQR81

Kind of pricey but good- don’t know if available in UK. Go on Covestro (Bayer) website for more specifics if you can’t get this one. Maybe others here can give better info.
jrburns47
Posts: 165
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Horizontal stripes - along same depth, like ISO lines...

Post by jrburns47 »

As you know, the HX200 is panchromatic. The work necessary for using photopolymer is pre-exposure (laminating without bubbles and dust to a clean substrate under dim safelight, not to mention good substrate prep) as opposed to post-exposure like silver halide. This is covered on the Covestro/Bayer website in support docs and videos. Completely different skill set but important to master if one intends to show publicly. Additionally, the aspect of archival protection and longevity for public display hasn’t been investigated yet as far as I’m aware.
SarahC
Posts: 7
Joined: Sat Oct 17, 2020 2:53 am

Re: Horizontal stripes - along same depth, like ISO lines...

Post by SarahC »

I see, thanks!

I've just had a look at my blue LED darkroom light with a little spectrometer, and it peaks at ~465nm.

The spectral absorption on https://geola.com/product/photopolymer/ shows 465nm blue is just a teeny bit higher than using a 660nm yellow safe light.
Save the pennies, and the holograms look after themselves. =D

Aren't indoor hobbies great for the lockdown? =D
I wonder if anyone's done a Covid scene with the virus particles floating around in a green tinted magical space.... I imagine the spikey critters would look rather good in a hologram - an excuse to have a lot of depth too.
If I may - something like this.... https://codepen.io/SarahC/pen/xxGbGEr
jrburns47
Posts: 165
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Horizontal stripes - along same depth, like ISO lines...

Post by jrburns47 »

I’m no expert although i’ve done a fair amount of research on the topic. Here’s a photo of a page of info from a Covestro flyer. Use at your own risk🤪😂😷!
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