Beyond "Wide open" and "Stopped down"

[matt_sachs]

Greetings, All:

 

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Forgive my ignorance here.

 

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Spinning the aperture dial on the 35mm lens, and looking at the diaphragm blades, there is an extra click beyond each of the marked extremes that affects the blades as expected. Are there 1/4-or-so stops (guessing the number here) beyond the stated aperture range that are "valid"?

 

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Matt Sachs

mattsachs@attbi.com

[geddert]

they are half click stops, not 1/4 click stops...

[ilkka]

The click stops in between full aperture markings are half stops.

But some Leica lenses apparently open up a bit more than the widest

aperture. For example my 2/35 aperture opens to about 1.8-1.9, after

the click marked 2. Leica is supposed to calibrate the aperture scale

exactly and has some leeway to be sure to always get the maximum

aperture, so some lenses open up a bit wider. I suppose the same

applies in the smaller end though my lens does not really close

beyond 16.

 

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Ilkka

[kristian dowling]

My 35mm Lux Asph and 90 SAA are the same.

[michael_darnton1]

"Valid" is a relative question. One of my meters reads in 1/10 stops.

Lenses are usually clicked in 1/2 stops, and film speeds, shutter

speeds, and lens openings traditionally progress in 1/3 stops.

Shutter speeds are variously accurate across brands, specific

cameras, and speeds within a single camera (Leica high speeds are

notoriouly off, usually). Cameras which automatically bracket

exposures, and people who do the same manually when they shoot,

usually work in 1/2 stops, which should tell you something (though

I'm sure someone will pop up who says he brackets in something like

1/50 stops, and can tell the difference in each frame--this is a

*Leica* forum, after all, with all the attendant nonsense!)

[michael_darnton1]

Ah, and I see I totally missed the point of the question! I'd go with

what the company set, and if you want to know if there's a

difference, test your individual sample and see if you see a

difference.

[richard_oleson]

At the wide open end, no: the maximum aperture is limited by the

diameter of the baffle in the barrel, opening the blades further into

it won't affect anything. At the small end, the blades probably are

overtraveling slightly as you go past the click, but it's probably

not enough to be of any use photographically.

 

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rick :)=

[boris_brecelj1]

Matt was not asking about the 1/2 stops between the markings

but about the extra ammount that some lenses open for

example 'chron 35/2 just a tad more towards 35/1.4.

 

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This is because every lens is individualy adjusted to be precise

35/2. How much is this extra "opening" depends on the lens but

it is neglectable little.

 

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Best regards,

[andy_piper2]

It varies from lens to lens just how much extra you 'get' - but it's

never enough to make for significant 'extra' speed or 'extra' DOF - my

35 f/2 opens up to about f/1.95 and stops down to f/17 or so.

 

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Large-aperture long lenses (90 f/2.0, e.g.) often have more visible

change at the wide-open end - but it's still actually adding only an

insignificant amount of light compared to the huge size of the f/2

aperture itself.

 

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The 21 f/3.4 I'm experimenting with is the opposite - it has a full

clickstop between f/4 and f/3.4 - same spacing on the ring as from f/4

to f/5.6. But the aperture blades disappear completely by the time I

turn halfway from 4 to 3.4. The actual hole in the glass is f/3.4 even

though the blades behind it move to f/2.8 or some such.

 

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Stopping down from f/3.4 to f/4 nothing happens until just before the

f/4 click stop - then a sliver of blade sneaks into the opening at the

last second. It's taking a little practice to get used to the idea that

'stopping down' a half click from f/3.4 is still f/3.4. =8^o