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

[DDTJRAC]

Photos eBay: Fair Use

 

[JensH]

Hi,

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

 

[DDTJRAC]

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.

 

[mshchem]

When in doubt I have a flashlight.

 

[Rick A]

It's a useless feature so I removed all the ones on my Beseler lensboards and put a strip of black tape over the hole.

 

[GregY]

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.

The thumbscrews are to help level the lensboard. The 45 MXT isn't the most user-friendly to level all the parts of the enlarger

 

[MattKing]

It's a useless feature so I removed all the ones on my Beseler lensboards and put a strip of black tape over the hole.

I was musing about this last night, and wondering whether they may have been of greater practical advantage if used with the higher power/greater light intensity found in some of the commercial printing setups.
I'm thinking of the big 220 volt, 5x7 Durst colour enlarger that friends had which threw off so much heat that they needed to add air conditioning to the darkroom, as well as the Durst miniprinter I used in a photofinishing lab for a while, where it was really, really difficult to actually see the aperture setting in order to check it.

 

[xkaes]

The thumbscrew are to help level the lensboard. The 45 MXT isn't the most user-friendly to level all the parts of the enlarger

Strange that I can't find any mention of them being used for "leveling" the lens board in my CB-7 or 45 MXII user manuals. Besides, there's nothing inside the lens board mount for the thumbscrews to push up against.

 

[xkaes]

I was musing about this last night, and wondering whether they may have been of greater practical advantage if used with the higher power/greater light intensity found in some of the commercial printing setups.

Certainly the brightness from the light pipe will depend on the light from the enlarger head, and that varies quite a bit, but I've used them, and they did illuminate enough for me to see better -- with the lenses I had. Of course my eyes must first adapt to the dark.

I no longer use them for other reasons, such as most of my lenses have illuminated f-stops, and the light pipes are useless on lenses in recessed boards..

 

[Rick A]

I was musing about this last night, and wondering whether they may have been of greater practical advantage if used with the higher power/greater light intensity found in some of the commercial printing setups.
I'm thinking of the big 220 volt, 5x7 Durst colour enlarger that friends had which threw off so much heat that they needed to add air conditioning to the darkroom, as well as the Durst miniprinter I used in a photofinishing lab for a while, where it was really, really difficult to actually see the aperture setting in order to check it.

They were barely usable on my 23C's and totally useless on my 45MXT with a cold light head. You need to aalign the aperture window on the lens with the light tube and it barely illuminates the numbers. Longer lenses need longet light tubes. Goofy and non essential feature.

 

[xkaes]

The light tubes appear to have come in different styles, and perhaps lengths -- two? Short & long? And apparently some were adjustable with a screw next to them -- see first photo -- but I've never seen instructions. The ones I have are not adjustable and the bases where they are attached to the lens board are slightly different.

 

[Alan Townsend]

I have a Rogonar 135mm enlarger lens mounted on an old Speed Graphic I use for an enlarger and occasionally for taking pictures and recently got fogged negatives from that built in illuminator on the lens collar rather than lens board. I also plugged it was black electrical tape on both sides. It only fogged film when the sun was at certain angles. This is a warning to those who have enlarging lenses on their cameras!