Newton-Finder with blue glass (9x12 about 1925) Why?

[Xipho]

Hello,

I have a 9x12 plate Camera which is equipped (I think as an extra) with a newton-Finder with a sqaure front lens with hair cross an a deep blue back lens.

This type I also find as acessory in a 1925 Ica Catalouge, called "Newton-Sucher Ideal"

Does anyone know why they used this dark blue glass? it makes the use of the findet difficult in low light I think... Should it be a "BW viewing filter" like there is one from Wratten, or what is the purpose?

thanks in advance!

[djdister]

From Camera-pedia:

Of course the inventiveness of camera developers didn't stop with the question "How can we combine the advantages of waist-level and eye-level in one finder?". One answer was a collapsible hybrid viewfinder. It had a front lens with crosshairs as a targeting aid, what was called Newton finder 100 years ago. With this combination it was an eye level finder. But when its cross haired mirror was put in at a 45 degree position behind the lens it became a smart waist level finder. Smart because the crosshairs of the lens and that on the mirror helped to find the perfect perpendicular viewing position of the eye over the finder.

http://camerapedia.wikia.com/wiki/Viewfinder
(at the bottom of the page)

[Drew Wiley]

If the camera was intended for blue-sensitive plates, then viewing through blue would allow you to see and compose the scene like the film itself. There are also
cases where focus shift was a risk due to poorly corrected lenses of the era, so they wanted you to focus only using blue light.

[Xipho]

just tell me how to focus with a newton-Finder?

[Jac@stafford.net]

just tell me how to focus with a newton-Finder?

You can't focus with a Newton finder. Sorry.

[Xipho]

whats wrong here? it was onlay a question why Ica used this blue glass? I find it very dark so it is difficult to use...

[Xipho]

I cettainly know that you cant focus with a newton finder, it was only a reply to a post who said that it s for focusing orthochromatic plates....

and my finder here is no hybrid finder with a mirror as postulated in answer 1...

[Oren Grad]

whats wrong here? it was onlay a question why Ica used this blue glass? I find it very dark so it is difficult to use...

Don't worry, your question is OK. We'll see whether anybody knows the answer.

[Jac@stafford.net]

I cettainly know that you cant focus with a newton finder, it was only a reply to a post who said that it s for focusing orthochromatic plates....

Thanks. I understand, now. I am puzzled by the dark blue as well, especially in a framing device. There were some discussions years ago on the subject of focusing using a blue filter, but they do not apply here. If it does not have optical properties other than the blue, perhaps removing it will obviate concern.

A parting shot in the dark - some old glass turns blue/purple over time especially when exposed to sunlight for a long time. You can sometimes find such in 19th century lenses, and especially some old glass bottles. (In fact the cause of it lead to the first hint towards lens coating, but application didn't happen until much later.)

Best of luck,
J

[Xipho]

no, it has optical properties, its a lens, I tried to remove it as i zhought it was not original, but then the finder does not work...
It is regular in this blue color, as it is listed 1:1 in the old ICA catalouge, where the blue color is confirmed, bit no reason for it is given.

Why is a question for a 9x12cm camera accessory in the lounge? Not LF enough?
then it would be better you maka a own forum cat for old plate cameras, and best would be a cat for "LF type MF cameras" like a technikardan or a baby technika. the lounge is a weird mix, and for thecnical similarity, you should adopt the smaller opical bench and technikas in your forum. Because here is where the best knowledge for such cameras is, not in a common MF Forum...