Ross Xpres 300mm f4.5 design

[Colin D]

I've got this lens, not looking to sell it, and wondered what design type it is. I'm starting to use it for still life shots and with some manipulation to the front element turning it into a soft focus lens. I've checked the catalogue on the camera eccentric site but am still none the wiser about what design it would be classed as. I have seen some people call it a Tessar design, but then others refute that as there was a patent problem using that design.

Apart from the fact that I have to dis-assemble it to put the f stop ring on the right way again because it reads in the reverse to the way it should I find it an interesting fast lens.

The following (poor quality compact digi) shots show that when it is wide open you can see two sets of three reflections, the third reflection at the back is extremely faint, with one of the spots having a blue colour cast (does that mean single coated?). When stopped down you can see two sets of two refections.

[Dan Fromm]

By both the VM's and P-H Pont's Ross chronologies your lens is post-WW II. Should be coated, should be a tessar type.

Recognizing tessars is easy. Pictures such as you posted are unfortunately no help at all.

Here's the test: unscrew one cell from the shutter. Hold each cell under a light bulb and count reflections. The front cell should have four strong reflections, one from each air-glass interface. The rear cell should have two strong reflections. If it really is a tessar type, it should have one weak reflection from one glass-cement-glass interface. If the myth is true and the real cell is a cemented triplet, it will have two strong and two weak reflections. The weak reflections may be hard to see.

[Colin D]

By both the VM's and P-H Pont's Ross chronologies your lens is post-WW II. Should be coated, should be a tessar type.

Recognizing tessars is easy. Pictures such as you posted are unfortunately no help at all.

Here's the test: unscrew one cell from the shutter. Hold each cell under a light bulb and count reflections. The front cell should have four strong reflections, one from each air-glass interface. The rear cell should have two strong reflections. If it really is a tessar type, it should have one weak reflection from one glass-cement-glass interface. If the myth is true and the real cell is a cemented triplet, it will have two strong and two weak reflections. The weak reflections may be hard to see.

Thanks Dan, the front cell certainly has four strong reflections, the rear cell has one strong reglection and one much weaker and smaller reflection at the rear. Does this last bit mean anything?

[Colin D]

Ok, next question about this lens. Does the f stop ring screw on or slip on? Someone has put it on back to front so that it works in reverse ie. @ f4.5 the lens is stopped down to f45, @ f45 it is wide open. If I can take the f ring off and turn it around it should fix the problem. The f ring is rigid and does not move with the barrel when I open and shut the blades. I've tried unscrewing it with my hands but it won't move, I've put a small screwdriver in the small gap between the ring and the barrel and tried to prise it loose but it doesn't move. I'm reluctant to force it too much for fear of doing damage. Any suggestions would be appreciated.

[Dan Dozer]

Ok, next question about this lens. Does the f stop ring screw on or slip on? Someone has put it on back to front so that it works in reverse ie. @ f4.5 the lens is stopped down to f45, @ f45 it is wide open. If I can take the f ring off and turn it around it should fix the problem. The f ring is rigid and does not move with the barrel when I open and shut the blades. I've tried unscrewing it with my hands but it won't move, I've put a small screwdriver in the small gap between the ring and the barrel and tried to prise it loose but it doesn't move. I'm reluctant to force it too much for fear of doing damage. Any suggestions would be appreciated.

Take a look all around the outside of the barrel. I have a lens about the same era that has a very (and I mean very) tiny screw that screws in thru the outside of the barrel that holds the iris in place. Removing the screw if there is one may free up the F ring.

[Colin D]

Thanks Dan, the f stop ring eventually unscrewed off the barrel and I was able to flip it and screw back on the right way. I found taking the screw out of the barrel simply disengaged the iris blades.

[Dan Fromm]

Thanks Dan, the front cell certainly has four strong reflections, the rear cell has one strong reglection and one much weaker and smaller reflection at the rear. Does this last bit mean anything?

It means (a) that you, like the rest of us, sometimes have trouble seeing a tessar rear cell's second strong reflection (hint, its at the rear surface) and (b) your Xpres is a tessar type.

Sorry, can't help with the mechanics.

[Colin D]

Cheers, thanks again Dan.

[DerrickStone]

By both the VM's and P-H Pont's Ross chronologies your lens is post-WW II. Should be coated, should be a tessar type.

Recognizing tessars is easy. Pictures such as you posted are unfortunately no help at all.

Here's the test: unscrew one cell from the shutter. Hold each cell under a light bulb and count reflections. The front cell should have four strong reflections, one from each air-glass interface. The rear cell should have two strong reflections. If it really is a tessar type, it should have one weak reflection from one glass-cement-glass interface. If the myth is true and the real cell is a cemented triplet, it will have two strong and two weak reflections. The weak reflections may be hard to see.

Are these lenses still available in the market? I am looking to get exactly these lenses so from where I will get them? Please help..

[Colin D]

Are these lenses still available in the market? I am looking to get exactly these lenses so from where I will get them? Please help..

Derrick, they appear on ebay occasionally. When I bought mine 6 months ago the seller had two, there was one last week going for $900, might still be there because I don't think it sold.