FSU lens irises (irii?)

[Terao]

Are they a throwback to much older lenses? Have never seen so many blades in a lens before! Seem to result in lovely soft bokeh, so why do modern lenses have fewer blades? Easier to build and more reliable or is there an optical reason?

 

[wolves3012]

Are they a throwback to much older lenses? Have never seen so many blades in a lens before! Seem to result in lovely soft bokeh, so why do modern lenses have fewer blades? Easier to build and more reliable or is there an optical reason?

I hadn't actually noticed till you mentioned it! The FSU lenses seem to have about double the blades of my japanese lenses. Yes, they are based on old designs.

The more blades, the nearer you can get to the ideal of a perfectly circular aperture. I can't see the "soft bokeh" being related to it at all, though I'm not a lens expert. I think modern lenses have fewer blades because they've found it's acceptably accurate with fewer and slightly cheaper to make.

 

[Spyderman]

Modern lenses have less blades? You mean cheapo SLR lenses, don't you?

'cos to me "modern lenses" means Leitz, Voigtlander, Canon L, Nikon expensive primes.

And definitely - more blades = smoother bokeh, but it's just one variable that influences bokeh. IMHO optical construction of lens is more important.

 

[xayraa33]

the 1930s Summar and some later Summitars have the hexagon pattern aperture blade, made up of less blades than the round pattern on most Summitars and Summarits.
the hex pattern aperture lenses still have nice bokeh.

 

[wolves3012]

Modern lenses have less blades? You mean cheapo SLR lenses, don't you?

'cos to me "modern lenses" means Leitz, Voigtlander, Canon L, Nikon expensive primes.

And definitely - more blades = smoother bokeh, but it's just one variable that influences bokeh. IMHO optical construction of lens is more important.

"Modern lenses" means either modern-designed or modern-built (or both).

I'm curious to know how you arrive at "definitely - more blades=smoother bokeh". Unless you have two otherwise identical lenses (unlikely) how do you know this?

"Bokeh" is such an abused word lately, it's in the final picture and the beholder's head. The factors that create it are manifold. I'm not flaming your post by the way, just adding my thoughts...

 

[ZorkiKat]

SLR lenses tend to have less blades because more blades in the aperture will make auto-diaphragm stop down mechanisms more complicated, move slower, and less reliable. Pre-set, non-automatic diaphragm lenses (eg the Jupiter-9) will have as many blades as their design would allow since the aperture is totally independent of any camera coupling.

The rounder, less 'cornered' aperture which many blades produce significantly influences the way blurs are produced. Blurs for the most part are really fused highlights. Round apertures produce smooth circular blurred highlights. An aperture with sharp corners will produce a cornered blurry highlight, and would therefore make blurs look less smooth. Of course the optical formula has the final say on how the lens makes its blurs - its bokeh quality.

 

[Valkir1987]

Can too much oil or grease on the aperture blades cause optical problems? (Like inner foggy reflections for example) My Jupiter-9 has a lot of grease on its blades.

Greetings

 

[Terao]

Modern lenses have less blades? You mean cheapo SLR lenses, don't you?

lol

I guess I've been used to 8-blade Nikon zooms and primes, even some 5 blade ones

Now I know Voigtlander make a lot of their 10-blade designs, but the Jupiter looks like it has 12, maybe 16?

The auto stop down requirement makes sense...

 

[santino]

Modern lenses have less blades? You mean cheapo SLR lenses, don't you?

is the 80mm Hasselbald CF Planar a cheap SLR lens? look at the blades and count...

 

[ZorkiKat]

Can too much oil or grease on the aperture blades cause optical problems? (Like inner foggy reflections for example) My Jupiter-9 has a lot of grease on its blades.

Greetings

Only if the oil migrates on the lens elements. Migration by flowing or through deposition of lubrication components which evaporate. Otherwise, the oil in the blades of a non-autodiaphragm lens shouldn't be any cause for concern.

OTOH, oily blades in an autodiaphragm lens would be a problem. These mechanisms need to run light and dry. Oil would stick the blades and make them heavier, causing problems in stopping actions.

Jay