Darlot 10" Landscape Lens

[bennoj]

I just won an auction for this lens (eBay Item number: 110113225322) and was hoping to get some input from those with more experience in older lenses. I plan on mounting it for my B&J 5x7, but might it cover 8x10? Fall off and lack of corner sharpness in 8x10 would be fine, I'm assuming a more pictorial quality in any case.

Thanks!

[nicolai]

Not to be an ass, but there's one way to find out! I've recently picked up several of these type and they all seem to have their own thing going on. Just try it!

[Jim Noel]

When I obtain an old lens of unknown covering power I mount it on one of the 8x10's and make three exposures on lith film. One wide open, one stopped half way down and one at the smallest opening.

I use lith film because it is cheap, sharp, and develops rapidly.

This gives me all the information I need to determine how the lens will be used on each camera.

Actually, I am dong this with 3 new lenses tomorrow.

[bennoj]

Well, the lens arrived today (typical for any lens bought off eBay, it had a nice greasy thumbprint in the middle of the glass),so I popped it into my iris mount on the 8x10 and took it outside. Even full open it covers 8x10 with ease with even illumination from corner to corner. Central sharpness with increasing blur towards the edges, which is just what I'm looking for right now. No markings on the 4 apertures, so I guess I'll be burning some Polaroids to figure that out.

[PHOTOTONE]

A 10" lens would techncally be a good portrait lens (head to waist), for 5x7. A good head and shoulders lens for 4x5, but a bit wide on 8x10. However now-a-days more people want to see the swirly bits so these old lenses are being used with larger film sizes than they were designed for.

[bennoj]

I've been searching around for an f-stop formula and found this one - F=A/FL (f-stop = aperture diameter/focal length). So I measured the 4 apertures and came up with measurements of 18, 13, 10 & 7mm. Converting 10" to 254mm, my f-stops come to 14, 20, 25, 36. Does this sound reasonable? I know, go out and shoot and see what you get. I just have never been the best with math so I'd like to know if I'm at least in the ballpark.

[athanasius80]

Don't worry about it too closely. I used the same formula and found that my Voigtlander Euryscope is f7.7, f11, f21, and f30 with the Waterhouse stops included. Close enough for me!

[Ole]

The F-stop formula is written on most older lenses, e.g. "F=150mm 1:4.5", or "1:4.5 / 150mm" or something of the sort!

F is the focal length, which divided by the diameter of the aperture opening gives the f-number.

I have a couple of little old lenses with wheel stops, where the holes are simply marked with a number. Measuring them I found that in one case there was no neat mathematical progression from one hole size to the next, nor did any of the holes correspond to any kind of "standard" number. So even if the wheel has been swapped withthat from another lens, it still doesn't really make sense.

So what? I've written a little "f-stop list" for the lens which I bring with me if I intend to use it (and if I can find the list). By now I remember approximately what the approximate f-value is for each hole - so I brought that lens with me to Italy and used it quite often. maybe even most - old cities invite wide-angle lenses. It's 3 1/4" Perken Son & Rayment 5x4" Portable Optimus...

[bennoj]

This lens has nothing inscribed other than Darlot, Paris and B.E. & Co. No focal length (double-checked that by measuring the distance to the film plane at infinity focus), no max. aperture, nothing on the wheel stops. I'll put the 4x5 back on my 8x10 and try the stops I calculated with some Polaroids and see how it goes. Now if only it would stop drizzling outside.

[John Kasaian]

Lucky! It sounds like quite a find---I've got a Darlot that just covers 4x5---its a lovely lens.