What is the purpose of this red light on the lens board?

[slackercrurster]

Photos eBay: Fair Use

 

[JensH]

Hi,

it illuminates the aperture ring.
So you can see what f stop is set in the darkroom...

 

[slackercrurster]

Thanks! In 55 years of photo work, first time I ever saw one.

 

[Ian C]

Clever in theory. Useless in practice.

The one shown in post #1 has the 45º bevel rotated 180º out of position. The bevel should be opposite the lens. The bevel is coated with silver paint that is supposed to reflect the light from the lamp 90º from the tube to the aperture scale. The light reflects from the reflective paint at bottom of the bevel, through the tube, and to the aperture ring.

Here are some photos of Beseler 23C lens boards with the pilot light tube in correct orientation.

https://www.bhphotovideo.com/c/product/4519-REG/Beseler_8037_50mm_Flat_Lensboard_for.html

https://www.bhphotovideo.com/c/product/4525-REG/Beseler_8029_39mm_Lensboard_with_5_8.html

https://www.bhphotovideo.com/c/product/4517-REG/Beseler_8023_39mm_Flat_Lensboard.html

https://www.bhphotovideo.com/c/product/4515-REG/Beseler_8021_39mm_Flat_Lensboard.html

Note the different tube lengths to accommodate the assumed aperture ring distance from the flat part of the board.

 

[JensH]

Thanks! In 55 years of photo work, first time I ever saw one.

Newer seen such, too. I wonder if it can cause problems when doing color enlargements...
Btw, later examples of the Componon-S 135 come with illumination from inside the barrel.

 

[john_s]

Clever in theory. Useless in practice.

The one shown in post #1 has the 45º bevel rotated 180º out of position. The bevel should be opposite the lens. The bevel is coated with silver paint that is supposed to reflect the light from the lamp 90º from the tube to the aperture scale. The light reflects from the reflective paint at bottom of the bevel, through the tube, and to the aperture ring.

Here are some photos of Beseler 23C lens boards with the pilot light tube in correct orientation.

https://www.bhphotovideo.com/c/product/4519-REG/Beseler_8037_50mm_Flat_Lensboard_for.html

https://www.bhphotovideo.com/c/product/4525-REG/Beseler_8029_39mm_Lensboard_with_5_8.html

https://www.bhphotovideo.com/c/product/4517-REG/Beseler_8023_39mm_Flat_Lensboard.html

https://www.bhphotovideo.com/c/product/4515-REG/Beseler_8021_39mm_Flat_Lensboard.html

Note the different tube lengths to accommodate the assumed aperture ring distance from the flat part of the board.

I notice in these illustrations that there are two thumb screws on each board, presumably to prevent movement. All my old Beseler boards have no such screws. When did they introduce this feature?

And I agree that the red light is too feeble to illuminate the aperture ring. I'm sure most people just count clicks from full open.

 

[xkaes]

Beseler had this feature on lots of their boards. It's not bright enough to fog any paper, but it is bright enough to illuminate some f-stop rings -- but lots of f-stop rings are internally illuminated already, so you might not need it. (Does anyone worry about their illuminated f-stop ring fogging paper?) Or the tube might not illuminate your particular f-stop ring for other reasons. If you don't want it on your lens board, it's easy to cut off -- and close up with a piece of black tape or paint.

 

[xkaes]

I notice in these illustrations that there are two thumb screws on each board, presumably to prevent movement.

Those tabs are to allow you to get the lens board on the enlarger without using the lens as a "handle". I've never found them useful except for recessed boards where it's hard to grab the lens.