Finally got my big lens mounted

Petrochemist · Jan 11, 2023

Right back in October 2021 I brought a job lot of five TV projector lenses. I've finally got round to mounting one of the two largest onto a lens board for my 5x4 monorail.
This lens is ~5"diameter and has a surprisingly short focal length - I make infinity focus ~150mm from the rear of the lens which makes it roughly a 150mm f/1.2. It's 2.2kg weight makes it unlikely I take it out for a hike!

These shots show it roughly focused on the back of a PC that was around 1.5m away, so the bag bellows will be appropriate for most non macro shots.
Coverage is excellent still covering the 5x4 glass with the front standard shifted all the way to one side, DOF is a challenge (especially when my loupe isn't handy) So far I've only got digital 'through the viewfinder' images from it. Perhaps I ought to make some waterhouse stops before wasting film with it.

nosmok · Jan 11, 2023

Cool! One of the problems with trying to put W-stops in these things (I have a Buhl film projection lens that's about 5" and f/pi-- 3.14) is that for best results the stop needs to be between the groups at the optical center of the lens. Although I guess if we're modding old projector lenses for LF work, we're already outside the boundaries of 'best results'.

pbromaghin · Jan 11, 2023

150/250 = f/.6?

abruzzi · Jan 11, 2023

5inch diameter would be 125mm, so 150/125=1.2

Petrochemist · Jan 11, 2023

nosmok said:
Cool! One of the problems with trying to put W-stops in these things (I have a Buhl film projection lens that's about 5" and f/pi-- 3.14) is that for best results the stop needs to be between the groups at the optical center of the lens. Although I guess if we're modding old projector lenses for LF work, we're already outside the boundaries of 'best results'.

Between the elements is best, but I've used shaped stops against the front element of another projector lens with few noticeable issues - one of them did cause vignetting, the others were fine.
Using a hat for a shutter, will be much more limiting for daylight shots, even with paper negatives (roughly ISO3) f/1.2 works out somewhat faster than I can expose. Perhaps if I can track down a working Thornton Pickard shutter in the largest size they made (which was I believe 5")...

I suspect this lens will work out suboptimal in quite a few ways, but it should be fun to play with (if the subject can be accessed by car)

AnselMortensen · Jan 11, 2023

That looks like a lot of fun!
I have Lens Envy now...

Petrochemist · Jan 11, 2023

AnselMortensen said:
That looks like a lot of fun!
I have Lens Envy now...

I could be persuaded to sell the second copy I have, but I think postage to the USA would be a bit expensive!

Dan Fromm · Jan 11, 2023

Shutter?

Petrochemist · Jan 12, 2023

Dan Fromm said:
Shutter?

Sadly none, (nor aperture).
I've considered trying to make a DIY shutter to mount on the front, but I suspect it might take my 10 years to get round to it.

I guess a Compound #5 would be about the right size, but I've never seen one & the cost would be prohibitive anyway.

Dan Fromm · Jan 12, 2023

Petrochemist said:
Sadly none, (nor aperture).
I've considered trying to make a DIY shutter to mount on the front, but I suspect it might take my 10 years to get round to it.

I guess a Compound #5 would be about the right size, but I've never seen one & the cost would be prohibitive anyway.

Thanks for the reply.

Re the Compound #5, its maximum opening is, if I recall correctly, 65 mm. I'm not sure one would do for you. There are industrial Compound 5s, with no diaphragm. I have one, hang it in front of a 900/10 Apo-Saphir.

Not to be nattering nabob of negativity, but even though I have an ex-aerial camera 100/2 TTH Anastigmat that I've used on a 2x3 Speed Graphic and have had a 6"/1.9 Dallmeyer Super Six, I have trouble thinking of good uses for a fast lens that I can't use with a fast shutter speed. In the dark with a slooowww shutter speed, sure, why not?, but in general use I don't get it.

FWIW, at the apertures I usually use, my TTH small monster is no better than smaller lighter plasmats in leaf shutters.

Anyway, good luck with your project.

Petrochemist · Jan 12, 2023

Dan Fromm said:
Thanks for the reply.

Re the Compound #5, its maximum opening is, if I recall correctly, 65 mm. I'm not sure one would do for you. There are industrial Compound 5s, with no diaphragm. I have one, hang it in front of a 900/10 Apo-Saphir.

Not to be nattering nabob of negativity, but even though I have an ex-aerial camera 100/2 TTH Anastigmat that I've used on a 2x3 Speed Graphic and have had a 6"/1.9 Dallmeyer Super Six, I have trouble thinking of good uses for a fast lens that I can't use with a fast shutter speed. In the dark with a slooowww shutter speed, sure, why not?, but in general use I don't get it.

FWIW, at the apertures I usually use, my TTH small monster is no better than smaller lighter plasmats in leaf shutters.

Anyway, good luck with your project.

Thanks Dan, yes looking at things more carefully 125mm is the overall size of the #5 shutter, so clearly not big enough.
It's use will certainly be limited, shooting the local harbour or pier at night is probably my best bet, though portraits using flash in a dark room should also be practical (I've recently heard a podcast where this was done, but DOF certainly makes things like that awkward).

I freely admit it's a mad option, but it was surprisingly cheap & mad fits me!

RalphLambrecht · Jan 12, 2023

Petrochemist said:
Right back in October 2021 I brought a job lot of five TV projector lenses. I've finally got round to mounting one of the two largest onto a lens board for my 5x4 monorail.
This lens is ~5"diameter and has a surprisingly short focal length - I make infinity focus ~150mm from the rear of the lens which makes it roughly a 150mm f/1.2. It's 2.2kg weight makes it unlikely I take it out for a hike!

View attachment 326371 View attachment 326373

These shots show it roughly focused on the back of a PC that was around 1.5m away, so the bag bellows will be appropriate for most non macro shots.
Coverage is excellent still covering the 5x4 glass with the front standard shifted all the way to one side, DOF is a challenge (especially when my loupe isn't handy) So far I've only got digital 'through the viewfinder' images from it. Perhaps I ought to make some waterhouse stops before wasting film with it.
View attachment 326376

Wow; this looks like a lot of fun

pbromaghin · Jan 12, 2023

abruzzi said:
5inch diameter would be 125mm, so 150/125=1.2

Hmmm. How did I magically double the diameter? Duh. Brainfart.

Petrochemist · Jan 12, 2023

pbromaghin said:
Hmmm. How did I magically double the diameter? Duh. Brainfart.

Are you perhaps more used to working with the radius? Doubling might be almost subconscious

pbromaghin · Jan 13, 2023

Petrochemist said:
Are you perhaps more used to working with the radius? Doubling might be almost subconscious

Nope. I specifically remember actually thinking 5x25=250. Getting old? Too many concussions? Not paying attention? Halfzheimers?

Finally got my big lens mounted

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