darlot lever stop hemispherical [Archive] - Large Format Photography Forum

jnanian

27-Jul-2009, 22:48

hi

i just dug up a lens i bought years ago ..
which i believe to be a 10 1/2 " darlot rapid hemispherical.
has anyone else gotten their hands on one of these ?
will it cover 8x10?
and has anyone removed the rear element and used it as a single ?
i stuck it on a big camera without the rear element and it had a HUGE image circle ...

any ideas what i should expect image wise?
i've shot with it on a speed graphic and loved what it did, but never
without the front or back, and never on a camera bigger than 4x5 ...

i'd LOVE to remove the throat that closes down the fstop "wide open"
better yet, maybe i'll just put the elements on a board without the barrel

thanks!

john

Toyon

28-Jul-2009, 07:27

These are wide-angle rectilinear designs. Their "rapid" lens did not have the lever stops because it only allowed 4 f-stops. Yours, if I remember correctly is designed to cover at least 11x14, possibly larger. The 8 1/4" is for 10x12. It is not designed as a convertible. There is a good reason for the small stop (f16), unless you are looking for distortions. These lenses can be astoundingly sharp (particularly in the center 20 degrees). They are also useful for their perfectly round stops. Darlot wide-angles are one of the best lenses ever and very undervalued IMO. It would be a mistake to damage it.

goamules

28-Jul-2009, 08:19

I have one of these, and it's a favorite. I've had a lot of Darlot lenses, but I think these are their nicest, and I keep this one. Their very earliest ones were actual hemispherical designs, but then they went to the easier to manufacture rectilinear design, but kept the name. Here is a period ad that shows their coverage.

I think any rectilinear can be soft if you use half of it. But you can look for one of the pillbox darlots (or other) achromat meniscus types, which already have one group, and without a stop are soft.

jnanian

28-Jul-2009, 10:57

toyon and goamules

thank you very much for the information about my lens.
i guess it is a wide angle hemispheric then :) i was kind of joking about
removing the throat, and i am looking forward to using it on a 8x10 when i get the chance.
the lens i bought for my 8x10 ( wollensak 1a triple ) is being used on a different camera
and i kind of like the idea of having a dedicated lens for my camera. it makes
things easier than too many lenses ( too easy to get carried away with lenses ).

thanks for posting the advert.
it is nice to see my lens cost more than a month's pay when it was new :)

john

jnanian

28-Jul-2009, 13:20

i just noticed mine has "040" engraved next to one of the levers ( the largest one "7" )
does that mean it is a #4 ( size ) "8 inches" according to the attachment ...
i will have to figure out the focal length again because the last time it seems that i might
have been way off ..

thanks again!
john

jnanian

1-Aug-2009, 09:19

i realized i misread the serial number,
it was obscured under the lens shade ...
5040 ...
i'll be sticking it on an 8x10 to see how it covers ..

thanks again!
john

goamules

1-Aug-2009, 10:14

Unfortunately, there are no (known) serial number to date references. My 5" covers whole plate easily. A 10" or even 8" will cover 8x10 no problem. It'd probably cover double that.

Eric Lohse

1-Sep-2009, 08:56

Hi all,
I acquired one of the wide angle hemispherical Darlots with a whole plate camera from Maine (R.O.C) I was curious about the numbers on the lens stop levers, 3, 5, 7. A few years back, my cousin in Germany gave me a reprint copy of "Atelier und Apparat des Photographen" ( Studio and Equipment of the Photographer)by Otto Buehler, copyright 1869, Weimar.
Reading through the section on lenses, he indicates the #'s represent the # of times the exposure must be increased from full aperture. i.e. 3x, 5x, and 7x for the smallest aperture. He also comments that the apertures are generally between 1/16th and 1/72nd of the focal length.The reason for the math is beyond me. Thought it might be of interest
Eric Lohse

Eric Lohse

1-Sep-2009, 11:55

A change to my previous post. Apertures were between 1/36nd and 1/72nd of the focal length. FWIW.
eric

David Aimone

29-Jul-2010, 06:17

I just picked up one of these on e**y. Does anyone here have more information on it? Or photos taken by it? The information I have on it is pretty sketchy (exact sizes, focal length and apertures). I'll be able to get a better idea once it arrives.

http://www.davidaimone.com/img/s9/v14/p637444704-2.jpg
http://www.davidaimone.com/img/s10/v17/p885081308-2.jpg

goamules

29-Jul-2010, 06:51

Most information known is already above. They didn't put a "No. 2" or a size on the lens, so to determine which you have (from the catalog above) you'll need to measure focal length. Good lenses.

David Aimone

29-Jul-2010, 07:36

It will be interesting to play with once mounted for the camera. First thing I'll do is try to figure out the focal length and then apertures.

Thanks!

David Aimone

2-Aug-2010, 18:24

This little lens arrived today, and I jury-rigged it onto my 4x5 just to take a look. It looks VERY promising from the ground glass. i can't wait to get it mounted on a board and use it.

A couple of things though.

First, I thought this would be much more of a wide angle than it is. But I guess being a 5 inch focal length it wouldn't be that wide.

Any easy way to tell for sure what the aperture of this lens is wide open, and with each of the aperture levers operating?

http://www.davidaimone.com/img/s9/v14/p626412032-4.jpg
http://www.davidaimone.com/img/s8/v11/p816509985-4.jpg
http://www.davidaimone.com/img/s10/v16/p919322769-4.jpg
http://www.davidaimone.com/img/s9/v14/p923737041-4.jpg

David Aimone

2-Aug-2010, 18:26

one more:

http://www.davidaimone.com/img/s10/v16/p616998275-4.jpg

serial number 539

goamules

2-Aug-2010, 19:56

Enjoy the lens, they're nice. They are about a 90 degrees, and are about F15, if I recall. You can measure that by dividing the focal length by the apparent width of the light circle looking from the front. If you read this post, there is a reasonable explanation of what the lever numbers mean.

Finally, the very early ones were a unique hemisperical design, later they changed to just a wide angle rectilinear...but kept the name. Check your serial number, I bet there is a digit you can't see under the hood, making it at least 4 digits, not 3.

Here are my no. 3 and no. 4.

Jon Wilson

2-Aug-2010, 22:17

These are nice lens. Here are are a couple of shots I took with my 6 inch WA Darlot at the local military cemetary last memorial day. One is a picture I took of David Bowie's and another solder's headstones and the other is another angle of the cemetary. These lens work well even with fuji provia. Jon

Brian Stein

2-Aug-2010, 23:42

Any easy way to tell for sure what the aperture of this lens is wide open, and with each of the aperture levers operating?

From the information provided by Eric #3 is 3x exposure ie 1.5 stops down; then #5 and #7 respectively 2.5 and 3.5 stops down.

If this was f16 to start with (how to work out base f stop is found elsewhere in this forum. Briefly requires you to first to work out focal length and then find exit pupil size and then calculate f stop=aperture/focal length) you would have

no stop: f16
#3 ~f26
#5 ~f38
#7 ~f53
If i understand correctly how the stops work, adding a #3 to a #7 just gives you a #7 and so on.

Jon it is interesting to look at old photos and see how sharp the plate negative based ones are: these old lenses were good, but I did not expect very much in colour!

David Aimone

3-Aug-2010, 06:10

Thanks to everyone for the exhaustive information. It's clearer now. I just have to estimate the focal length and everything else should fall in place. Those apertures are small enough I may not even have to use a shutter all the time.

David

David Aimone

3-Aug-2010, 14:12

Ok, to measure the focal length on this lens, do I measure from the plane of the shutter, the front of the lens or the back? From the shutter to the rear focal point at infinity is about 6" or about 150mm. From the rear of the lens it's about 5.5 inches or 140mm. From the front about 6.5 inches or 190mm. The front lens diameter (glass) is about 1.25 inches.

My guestimate is that the shutter full open is about 12mm; with the 7 lever about 7mm; the 5 lever about 5mm; 3mm for lever 3, which makes sense with the numbers on the levers.

So if I assume it's 6" (which doesn't fit the old brochure posted in this thread), the wide open aperture would be f/12.5; lever 7 at f/22; lever 5 at f/30 and lever 3 at f/50 (f/11.6, f/20, f/28 and f/47 at 5.5 inches).

Am I even in the ballpark???

jnanian

3-Aug-2010, 14:45

when i did the measurements and calculations for mine
i came to the conclusion that the numbers on the levers
were the aperture size in millimeters.
it wasn't hard to convert the focal length to metric and divide.
my apertures ended up something like 16-11-8-5.6(open) ...
i am not a stickler for exact numbers so if they are a little off,
i don't worry about ( i am currently shooting paper negs with the lens ) ...
when i was using the lens on a 4x5 with film, i used the same
computed fstops and they were fine as well ... so i couldn't have been too far off.

have fun with your new lens !

David Aimone

3-Aug-2010, 15:26

jnanian,

I'm not a stickler either, but I want to be in the ballpark.

if you ended up with 16-11-8-5.6(open), can I ask what focal length you based that on and what the diameter of your front lens is? I just want to make sure I'm going through the process correctly, especially since your numbers are quite different than mine. I thought somewhere you mentioned a 8 or 10 in focal length. If so, my calculations would come out different than yours.

david

Thanks!

it wasn't hard to convert the focal length to metric and divide.
my apertures ended up something like 16-11-8-5.6(open) ...
i am not a stickler for exact numbers so if they are a little off,
i don't worry about ( i am currently shooting paper negs with the lens ) ...
when i was using the lens on a 4x5 with film, i used the same
computed fstops and they were fine as well ... so i couldn't have been too far off.

have fun with your new lens !

Steve M Hostetter

3-Aug-2010, 15:50

I have the 210mm and it covers 11x14"

jnanian

3-Aug-2010, 15:56

jnanian,

I'm not a stickler either, but I want to be in the ballpark.

if you ended up with 16-11-8-5.6(open), can I ask what focal length you based that on and what the diameter of your front lens is? I just want to make sure I'm going through the process correctly, especially since your numbers are quite different than mine. I thought somewhere you mentioned a 8 or 10 in focal length. If so, my calculations would come out different than yours.

david

Thanks!

yeah, my math and focal length and aperture calculations seem to be (way) off ...
my focal length i calculated to be about 8", the glass in front measured to be
just over 1.5" ...
i am probably way off i my fstops, but as i said, they seem to work fine for what i am
doing so i am not going to worry about it at this point :)

good luck!
john

both the attached images shot wide open with f/b paper,
guesstimating the asa to be about 6

David Aimone

4-Aug-2010, 06:29

Yes, there was a "1, " under the hood. Hard to see, and with quite a bit of space after the ","...

Finally, the very early ones were a unique hemisperical design, later they changed to just a wide angle rectilinear...but kept the name. Check your serial number, I bet there is a digit you can't see under the hood, making it at least 4 digits, not 3.

goamules

4-Aug-2010, 06:29

To get a proper aperture measurement, especially your wide open one, measure the circle of light you see holding the lens up, not the glass diameter. F5.6 is way to fast for these, they are around f11 wide open.

David Aimone

4-Aug-2010, 06:32

So f/11.6, f/20, f/28 and f/47 would be reasonable for wide open to smallest lever?

To get a proper aperture measurement, especially your wide open one, measure the circle of light you see holding the lens up, not the glass diameter. F5.6 is way to fast for these, they are around f11 wide open.

goamules

4-Aug-2010, 06:42

The starting point sounds spot on. Again, I've never figured out what each of the levers were. But I usually follow the premise that most lenses are sharper stopped down a little, so I use the middle aperture lever.

David Aimone

4-Aug-2010, 06:54

Thanks, Garrett. That gives me some place to base assumptions on for this lens. As soon as I get it on a board, I'm going to give it a road test!

Steve M Hostetter

5-Aug-2010, 15:01

Ok , here's my question.. I have this lens but maybe in a different focal length. I assume it's a 210mm but not totally sure now that I have read this link in detail so,,,

The highth of the lens from the flange is 1-1/4" and the width of the glass element on the front is 1-5/8" diameter.

The diameter of the max aperture is 1/2".. The back element is the same diam as the front .. I have three levers that have the numbers 4-7-8 ,,, can someone help me with the intendend aperture given for each designated number..
I have mounted this lens on my 11x14 and it covers If that helps to determine what true focal length and apertures..
Thank you so much for your time guys..!
regards
steve

David Aimone

5-Aug-2010, 15:20

Steve,

Do the aperture openings in millimeters match the numbers on the levers? On mine, they do, but my lens is a smaller version. That would make sense since my lens opening is 12mm wide open, then 7, 5 and 3 which is what is indicated on the levers.

David

Steve M Hostetter

5-Aug-2010, 15:48

Hi David,

#7 = 5/16" diam, #4 = 1/8" diam, #8= 1/4" diam

steve

David Aimone

5-Aug-2010, 16:13

Steve,

I may be totally off (I'm just trying to figure this out), but if you convert your inches measurements to mm you get roughly 12.7mm wide open, then 8, 6.3 and 3.2. If you divide 210 (your presumed focal length by each of these, you should have your f-stops (i.e., 210 / 12.7 = around f/16)

Does that make sense?

David

Steve M Hostetter

5-Aug-2010, 16:29

Ok, wide open is 13mm, #8 looks like 8mm, #7 looks like 6mm, #4 looks like 4mm

can you plase conver the others?

David Aimone

5-Aug-2010, 16:49

Ok, wide open is 13mm, #8 looks like 8mm, #7 looks like 6mm, #4 looks like 4mm

can you plase conver the others?

210/13=f16;
210/8=f26;
210/6=f35;
210/4=f52

Is that what you meant?

David