This is the best ever wide field 8X10 lens.

Same as the Computar and Kyvytar, and in a shutter it does achieve the advertised f6.8

They were sold as Kyvytar convertible to 370 I think. Nobody ever bothers doing that but it's certainly possible. Just take the front off, and double what the aperture is telling you and you'll be close enough.

These will cover an honest 410mm. That gives you a full 2 inches in every direction to play with movements. Sandy King says they'll cover 11X14 stopped down but I could never make them work for that. 10X12 is believable though. Or buy the 5X14 from me and this would be your dream lens!

These are not technically rare, but it's rare to see them for sale because they're such a delight to own, no one ever sells them. $615 includes shipping in USA