I have been given a selection of Kodak Wratten Gel Filters 3 x 3 inches and was wondering what is the best way to attach them to the lens.
Because they are only 3 x 3 inches, they do not cover the width of my 90mm lens but will cover the width of the 150mm lens
Years ago used to epoxy a small piece of steel flush with the rear of the lens. 3x3 inch gels were held in place by a small magnet on one corner of the gel. In this way I could fully utilize the 3 inch dimension. Kodak did market two piece black metal gel holders but the opening in them was only 2 1/2 inches in diameter. Many times did mount a 3x3 inch filter behind a lens whose rear diameter was more than 3 inches without problems.
There are several sources for 3 inch gel filter holders, including Lee and probably Cokin too. These sandwich the filter between two metal plates, obviously with a hole in it, and then this is used in conjunction with a threaded adapter to match the specific filter thread size on your lens.
Originally Posted by Drew Wiley
Ah, thanks for that, Cokin may be the cheapest option, I will go investigate. Thanks for the speedy reply
On a side note, can these filters be attached to the rear of the lens inside the bellows ?
They were subject to fading with exposure to light and heat. Before spending time and money on them make sure that they are still the marked value and are free from fingerprints.
Wratten gels are (were) such a standard that there are ratings on their stability to light. They are graded (A to D) for long term, short term, and high intensity exposure. These are available, along with the transmission, in the CRC Handbook. Yellow, orange, and red are very good, AAA. Tri-color green is BBC and tri-color blue is BBB.
I use gels and acetates. 3" gels will cover all my lenses from 58 to 450 except the 72mm. Not sure what your 90mm is, but if it is 67mm thread, then 3" will cover. As a bonus, as you stop-down the lens, that area of the filter required is reduced also and your filter doesn't really need to be full diameter. Check this for yourself.
I've seen people attach the filters with a single little piece of tape to the rear element inside the camera. This is very good as the wind doesn't bother it and it isn't causing flare or sparkles. Another technique that I use is to cut a 4" square of foam core. Cut a circle in the foam core such that it exactly slides onto your 90mm with a snug slip fit. In use, you will slide it to exactly flush with the front of the lens' front thread. Add little stick-on 'corners' to the foam core such that you can insert the filter and cover the opening. Hope that makes sense. You can make little frames of 2-ply mat board and tape the gels to this. It gives you better handling and you won't fold the filter.
Today, gels are very expensive and they have always been delicate. Acetates are better, IMHO, and cheaper. I make them really cheap (and some people will hate this) by buying the equivalent lighting acetate that is 24" square and cutting out whatever I need. In 24" I can always find (lots) a spot that is optically perfect.
Best of luck.
--ejw--
Great tip, I have now made a series of these and they look as though they will now do what I want. Thanks for all the comments.You can make little frames of 2-ply mat board and tape the gels to this. It gives you better handling and you won't fold the filter.
Acetate is optically inferior to true gel, and placing a filter behind a lens will further compromise the image. I have seen people tape gels in front of a lens, but being fragile and expensive, and with tape residue being a headache to remove, it never seemed like a good idea to me.
Yes, with the proper adapter.
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