A 1000mm rear element for the Nikkor T-ED 600/800/1200mm lens set?

[Stephen Willard]

I am considering paying for the manufacturing of 1000mm rear element lens for the Nikkor T-ED 600/800/1200mm convertible lens. My motivation is because of the 400mm jump from the 800mm rear element to 1200mm rear element. I have had many occasions where I could have used a 1000mm rear element lens.

Initially, I started out by looking for the Schneider Tele-Xena 1000mm lens on eBay and other places for that past eight years. I have not found one yet.

The initial cost for design and tooling would be around $35,000 which is not cheap. There may be ways to drive down the cost, but its still going to be expensive. I am interested in seeing if people who own the 1200mm lens set would be interested in purchasing a 1000mm rear element. The price could range from $800 to $1000, but that is just a guess. It could be cheaper or it could be more depending on how many elements I make.

The f-stop scale would be printed on a laminated pocket card and would not be a full f-stop difference. It would be more like a 1/3 or 2/3 stop increase or decrease form the adjacent scales of the 800mm or 1200mm scale depending on which scale you are referencing.

So, for those you who own the Nikkor T-ED 600/800/1200 lens set, would you be interested in purchasing a 1000mm rear element?



This is not a commitment to make a purchase, but rather an attempt to see what interest people have for such a rear element.

[Maris Rusis]

If I had a 1200mm lens and I wanted to convert it to a 1000mm lens (approximately) I'd just add a 0.25 dioptre lens to it. An achromat 0.25D would be preferable but considering the low power of such a supplementary lens a single element may be ok with a bit of stopping down.

[Pere Casals]

I'd just add a 0.25 dioptre lens to it. An achromat 0.25D

I've been experimenting with that, using eyeglass lenses (before cutting) behind the LF lens, it can be found in 70mm diameter, high quality PC, and with all sorts of coatings.

I'd ask, could this also it be used like the achromat ?

I guess that the eyeglass lens optimal placement distance may be important...



In fact I was experimenting to get "effects" in the image, but sadly the image was pretty good , wider anyway...

[ic-racer]

I believe this $500 high-quality adapter clamps on the front of lenses up to 114mm in diameter. It is 0.7x, I suspect, if you look around you can find something similar in a 0.8x (0.8 x 1200 = 960mm).

[Stephen Willard]

I believe this $500 high-quality adapter clamps on the front of lenses up to 114mm in diameter. It is 0.7x, I suspect, if you look around you can find something similar in a 0.8x (0.8 x 1200 = 960mm).

Hi ic-racer, Could you tell who manufactures your adapter?

[Mark Sampson]

It's heresy, I know, but I'd just use the 800mm lens and crop the negative to the desired image. One less thing to think about (and to carry into the mountains) and to deal with.

[Nodda Duma]

I checked the math on adding a diopter lens to the 1200mm lens to achieve 1000mm focal length. You actually want to combine the 1200mm lens with a 0.167D, or 6000m focal length lens. A singlet would work fine but are hard to find as a stock item. So adding a combination of two lenses (a positive and a negative, separated by a calculated distance) would be the way to achieve the necessary diopter with better optical quality than a reading glass lens.

Edit: mounting OptoSigma SLB-100-700P with Ross Optical L-PCC089 in a cell separated by ~50mm will give you ~6000mm focal length lens. Mount this behind your 1200mm lens and you'll have 1000ml focal length. Problem is the Ross lens is only 2" diameter.

Alternatively, OptoSigma SLB-50-5000P is a 5000mm focal length singlet which, if mounted behind the 1200mm objective will give you about 975mm focal length but again, only a 2" diameter lens