A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can build

[J. Patric Dahlen]

No, the Cooke is inherently a better design because there are enough variables to correct for all the Seidel Aberrations. The doublet / meniscus combination is short 2 needed to correct them all, as well as not being a symmetric design.

Excellent points, and it makes me wonder why they came up with the idea in the first place. Maybe it was cheaper to make despite the cemented doublet?

In this day and age, the number of air-glass interfaces are inconsequential thanks to coatings...there will be no contrast advantage.

True, but the Aldis Uno was designed in 1900 or thereabout.

[Nodda Duma]

Excellent points, and it makes me wonder why they came up with the idea in the first place. Maybe it was cheaper to make despite the cemented doublet?

Very likely..that and it was "good enough"

[Nodda Duma]

I have enlisted the help of an enthusiastic mechanical engineer. Would it be useful if he were to generate a model / layout of a lens barrel for these optics?

[brandon allen]

My 4x5 folder and accompanying wooden tripod projects are now complete. I suppose making a lens would be the next logical step...

What sort of performance could one expect from this lens design? Would it be comparable to commercially made lenses? Certainly making images with a self-made lens would be worth a lot, but would building this lens be really "worth it" as far as how well it would function? (Assuming it was built properly)

I think what I'm trying to do is talk myself out of starting this project...

[Nodda Duma]

I wouldn't rely on it as your only lens but as you stop down it should transition from soft to sharp in a pleasing manner.

I took some RMS spot size data down for you to review. By convention I believe the desired circle of confusion for 4x5 film is ~0.11 mm or less.

See attached, showing spot diameters for various points on the film plane. Hope this helps and my apologies for it being a non-film image.

[brandon allen]

I have enlisted the help of an enthusiastic mechanical engineer. Would it be useful if he were to generate a model / layout of a lens barrel for these optics?

That would certainly help me!

[pdh]

When you have some idle time (!), Nodda, would you be able to scale this for 8x10?

[Nodda Duma]

Sorry pdh, I had tried that originally. It is easy enough to scale the design on paper, but the available catalog lenses don't support the larger format.

Even this size was hard. That's why the lens is not faster than it is.

If I made the center flint custom then it's much easier. But then they wouldn't be all catalog lenses.

[pdh]

I did wonder if that was the sort of problem. thanks for replying.

[StoneNYC]

Sorry pdh, I had tried that originally. It is easy enough to scale the design on paper, but the available catalog lenses don't support the larger format.

Even this size was hard. That's why the lens is not faster than it is.

If I made the center flint custom then it's much easier. But then they wouldn't be all catalog lenses.

So I guess no lenses for 14x20 then... Shame...