I FINALLY Understand... Bokeh & Aperture Roundness

[E. von Hoegh]

Just buy a set of Dagors.

[Oren Grad]

I'm hoping that I can gain quite a bit by simply moving my modern lenses into shutters with very round apertures.

Please - save your money. You will be disappointed.

[Old-N-Feeble]

Oren... Thanks. I have lenses in #1 shutters that I can swap a modern lens into. I'll try before I buy.

[Old-N-Feeble]

Are post-1950 dialyte's and their variants close enough?

Just buy a set of Dagors.

[Dan Fromm]

Are post-1950 dialyte's and their variants close enough?

No no no.

Dialyte: (( )( | )( )) , where | is the diaphragm. Four air-spaced elements, eight glass-air interfaces

Dagor ()(( | ))() , where | is the diaphragm. Six elements, cemented into two triplets, four glass-air interfaces

You want a Dagor, buy a Dagor or a Dagor clone.

There are many clones, to learn about them buy a copy of A Lens Collector's Vade Mecum. Dan Colucci, who posts here as ccharrison, sells it. Cheap and worth the money.

[Old-N-Feeble]

Thank you, Dan. As usual you're post is brutal but learned, helpful and honest. I can respect that. I'll buy a copy of the Vade Mecum.

Does it address issues such as bokeh and aperture design?

[Dan Fromm]

No. Hokum is a modern concept largely confined to North America. The bulk of the VM was completed before the idea surfaced in its modern form.

Aperture design? What's that? To a first approximation, a hole is a hole.

[Ken Lee]

As a general proposition, the longer the lens, the greater the blur.

One way to get a peek at the blur without having to make a photo, is to point the lens at a distant white spot (a small round light bulb in a darkened room is good), and move the lens to focus closer and farther from the subject. Also tilt the lens partially away, so that the point moves away from the center of coverage. You can see what kind of aberrations that the lens produces: uneven dots with rings and ellipses versus smooth and uniform spots with soft edges.

One way to avoid having to remount all your lenses, which can be expensive and time-consuming, is to use a Sinar Copal Shutter - either by using a Sinar Camera or making an adapter for your current camera. That way, you can get barrel-mounted lenses, which usually cost less than shutter mounted lenses, and which almost always have diaphragms with many blades. The Sinar Shutter pays for itself the first time you buy a barrel-mounted lens.

For more information and sample photos, see here and here.

Here's one made with a barrel-mounted 250mm Carl Zeiss Jena Tessar on 4x5. The lens was not wide-open (f/4.5) but rather around f/9: small enough to keep the subjects in focus, but wide enough to render the distance with a soft blur. That lens has 18 blades if memory serves me right: it is round at all settings.

[Lachlan 717]

Aperture design? What's that? To a first approximation, a hole is a hole.

And if you're shooting wide open to maximise OOF, then it's rendered moot by the iris being fully retracted.

[cdholden]

There's the Packard shutters for use with more lenses because Packard shutters vary from small to very large. They're especially good for use with slower film and/or when you have a lens that won't fit on a 5.5" Sinar board.