• Ultraviolet Photography
  •  

Wratten 94A

12 replies to this topic

#1 A Stranger In The Wind

    A Stranger In The Wind

  • Members
  • 75 posts
  • Location: Calgary, Alberta Canada

Posted 12 September 2020 - 03:46

Canon 5Ds Converted Full Spectrum + Zeiss 50/1.4 ZF-IR

The Wratten 94A gives white foliage and a purplish sky.
Posted Image

A slight adjustment of Hue and darken blacks(if needed) gives it a nicer bluish color. No other adjustments applied.

Posted Image

Posted Image
Robert Chisholm

#2 A Stranger In The Wind

    A Stranger In The Wind

  • Members
  • 75 posts
  • Location: Calgary, Alberta Canada

Posted 12 September 2020 - 03:51

Posted Image
Robert Chisholm

#3 Cadmium

    Member

  • Members+G
  • 3,749 posts

Posted 12 September 2020 - 04:14

Stranger, Very lovely photos. :smile:
I can not find any Wratten 94A filter online or in my many Wratten catalogs. I can't find any graph for it.
Are you certain that filter is "94A". I just can't find that, and is not in any catalog. There is a 94, however it has no IR transmission, so it can't be simply the Wratten 94 which only transmits 400-500nm.
Thanks.

Edited by Cadmium, 12 September 2020 - 04:16.


#4 A Stranger In The Wind

    A Stranger In The Wind

  • Members
  • 75 posts
  • Location: Calgary, Alberta Canada

Posted 12 September 2020 - 04:39

Yes 94A. I also have a 94. I bought a bunch of current and discontinued Wratten filters many were never opened when I was shooting Kodak's Color Infrared slide film many years ago. A couple of weeks ago I tested every Wratten, Rosco, Lee and glass filter I have. 6 days straight shooting on my Full Spectrum camera. Over 600 filters were tested.

I have not seen a transmission chart in any of my Wratten books but the Wratten Envelope it came in identified it as a 94A
The 94 and 94A are very close from my test shots there is a subtle difference in the darkness of the sky. The 94A being slightly darker.

Both tests were shot with Coastal Optics 60
94
Posted Image

94A
Posted Image

Edited by A Stranger In The Wind, 12 September 2020 - 04:47.

Robert Chisholm

#5 Adrian

    Member

  • Members+G
  • 166 posts
  • Location: Ashtead, Surrey, UK

Posted 12 September 2020 - 09:53

Here is a page from the book: Kodak Wratten Filters, 3rd ed. from 1967. It does not show a 94 A

Adrian

Attached Images

  • Attached Image: Wratten 94.jpg

Adrian Davies
www.imagingtheinvisible.com

#6 Adrian

    Member

  • Members+G
  • 166 posts
  • Location: Ashtead, Surrey, UK

Posted 12 September 2020 - 09:53

Here is a page from the book: Kodak Wratten Filters, 3rd ed. from 1967. It does not show a 94 A

Adrian
Adrian Davies
www.imagingtheinvisible.com

#7 Andy Perrin

    Member

  • Members+G
  • 3,341 posts
  • Location: United States

Posted 12 September 2020 - 10:28

This is very interesting - I wonder what this filter is. It sounds like it might be a very rare beast indeed, maybe something discontinued early (or made for a very short time, so not appearing in most catalogs except for whatever period it existed for).

#8 colinbm

    Member

  • Members+G
  • 1,988 posts
  • Location: Australia

Posted 12 September 2020 - 11:38

View PostAdrian, on 12 September 2020 - 09:53, said:

Here is a page from the book: Kodak Wratten Filters, 3rd ed. from 1967. It does not show a 94 A
Adrian

Thanks Adrian
It must come back up in IR again ?

#9 JMC

    Member

  • Members+G
  • 1,094 posts
  • Location: London, UK

Posted 12 September 2020 - 12:44

Robert, what happens if you use your 94 and 94A with a non modified camera? In theory the 94 should give a blue image assuming it matches the transmission graph in Adrian's post, and it might be useful to see if the 94A is similar.

Also if you hold them up and just look through them, can you see anything? For the 94 you should expect about 10% transmission in the blue.
Jonathan M. Crowther

http://jmcscientificconsulting.com

#10 A Stranger In The Wind

    A Stranger In The Wind

  • Members
  • 75 posts
  • Location: Calgary, Alberta Canada

Posted 12 September 2020 - 16:06

I can see a 60 watt light bulb through it but forget about through an OVF. All shots I did on the modified and unmodified camera was using live view.

5DsR Zeiss 50/1.4 ZE ISO1600 shot at F1.4 Handheld. 1/125s - For a proper test I should use tripod but gives you the idea. Not as bright this morning the smoke from the US fires is starting to arrive Calgary.

Posted Image


On the modified it was midday and I was shooting ISO100 or ISO 200 shuttered speeds varied from 1/160-1/320sec and lens at F8. The ZF-IR lenses I have are all F mount and I use a chipped adapter that records EXIF of Focal length 100mm and F2 when used on my Canon cameras.

My guess is that both the 94 and 94A has some IR leak based on shutter speeds and low ISO on the converted camera.

A few of my wratten filters had notes inside stated these were new filters and their stability over time was unknown. Limited duration runs.

From looking just through the filters themselves I think the 94A is an offshoot of the 94 with less Blue transmission.

I am thankful I bought the filters several years ago as several old-time photographers and some dealers were getting rid of these filters as no one was using wratten filters anymore. It was in the early days of digital and I was still shooting heavy into shooting Kodak EIR Color Infrared slide testing it with every filter I could get ahold of. Fast forward to today I have seen some (not 94A) advertised on the bay upwards of $200 each.

A shot from yesterday of my sister's California Poppies no sky in this one.
Posted Image
Robert Chisholm

#11 A Stranger In The Wind

    A Stranger In The Wind

  • Members
  • 75 posts
  • Location: Calgary, Alberta Canada

Posted 12 September 2020 - 16:19

Found it:
Explanation of the 94A - Note supplied with filter
Notice
Due to the unavailability of certain dyes and manufacturing process difficulties, it has been necessary to slightly alter the spectral properties of the KODAK WRATTEN Gelatin Filter No. 94. The resulting filter has been assigned the Number 94A. The spectral transmission of this filter matches the data as published for the 94 that it replaced, but differs very slightly at the densities higher than those published. It is expected that the performance of this filter will meet most if not all, of the transmittance requirements of the previously supplied No. 94 filters.
Robert Chisholm

#12 Andy Perrin

    Member

  • Members+G
  • 3,341 posts
  • Location: United States

Posted 13 September 2020 - 04:17

Well there we go. You have to wonder how many 94A's still exist now.

#13 dabateman

    Da Bateman

  • Members+G
  • 2,042 posts
  • Location: Maryland

Posted 13 September 2020 - 06:09

The closest now would probably be 3 sheets thick of Lee 713.

As it looks like roughly 8% at 450nm to me.
The dye is mostly likely similar to wratten 47, as it too needed to switch to 47A. But this 94A looks like more than double the density of 47A.

Edited by dabateman, 13 September 2020 - 06:11.