Archived posting to the Leica Users Group, 2005/03/12

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Subject: [Leica] RD-1 users: Light loss with fast lenses?
From: bdcolen at (B. D. Colen)
Date: Sat Mar 12 05:14:19 2005

Olympus has two f2 zooms - f2 throughout the range - 35 mm equivalents
of 28-70 and 70-200 - which means f2 from 28 to 200...When you think
about it, this means that that DSLR will have glass as fast as that used
by the vast majority of M users, most of whom do not have any 1.4

While I really want some 1.4 primes for my digital, I've already found
that I can do pretty well at f2 at 800 iso in low having two
zooms that that me from 28-200 at f 2 all the way will be quite
neat..also, remember that these lenses will really me 14-35 and 35-100,
which means they will be extremely compact for their focal lengths...

As to the testing to see what f stops the old lenses really
provide...piffle...;-)...just shoot...and then look. That's what so nice
about digital - no need to do extensive testing with the newspapers on
the wall...process the damn film... Go to the dark room...just
meter...shoot...chimp...check the histogram, and get to work...:-)

-----Original Message-----
[] On Behalf Of
Peter Klein
Sent: Friday, March 11, 2005 4:36 PM
Subject: Re: [Leica] RD-1 users: Light loss with fast lenses?

Thanks, Henning and B.D.  I find it interesting that the fastest lenses 
specifically designed for DSLRs so far have been f/2, and most are 
slower.  Why?  Is it just marketing--they guys with spreadsheets have 
decided that "the public" wants mostly slow zooms, plus or two f/2 or
macros? Or are there some genuine technical reasons why lenses faster
f/2 are a problem for digital as things stand now?

There is a Sigma 30/1.4 announced, which should be available for C and N

first, and for the E-system after that. I will be very interested in how

this lens performs.  I am also very interested why a third-party lens
is coming out with a superspeed "normal" digital lens before  the major 
manufacturers came out with their own.

There actually is relevance to Leica in all this.  I always keep coming 
back to available light.  So I want to use fast lenses.  Eventually I
a digital RF, though the R-D1 wasn't that camera for me.  I wonder
my Leica and V/C f/1.4  and f/1.5 lenses are going to give me the same 
speed on digital as on film.  It was quite disconcerting to discover, on

the E-1, that when I opened my 50/1.4 from f/2 to f/1.4, I only got a
of a stop more light.  I honestly think it's more than just a t-stop vs.

f-stop issue.  I think sensor issues such as Henning mentions are

That's the reason for my question about the full speed of fast lenses on

the R-D1.

Add to the mix the fact that film lenses at both full and minimum
meter in odd ways on DSLRs. The same Olympus 50/1.4 lens mis-meters in 
opposite directions on different DSLRS--underexposing wide-open on an
overexposing on a Canon 300D and the Olympus E-300.  My old Vivitar
zoom meters the same shutter speed at f/11 and f/16, giving a one-stop 
underexposure at f/16.

None of this prevents using fast film lenses, but you have to do some
to know how your own equipment works.  Squirrely stuff happens at the 
extreme ends of that aperture dial.  My 50/1.4 OM lens takes great
at f/2, but there's not so much point in opening it to f/1.4 as there
be with film.  I hope a Summilux won't suffer the same fate on a digital


At 10:54 AM 3/11/05 -0800, Henning Wulff wrote:
[explanation of T-stops deleted for space]

>  should add that older lenses especially, and then rangefinder lenses 
>on the R-D1 in particular, will have more fall off at the corners as 
>discussed here and at various other places, _and_ will also have 
>somewhat lower exposure levels at the center with fast lenses due to 
>the edge rays necessarily striking the center more obliquely when the 
>lens is used wide open, and thus exhibit some of the same 'vignetting' 
>at the center due to non-perpendicular rays.
>It might be that the E-1 is more sensitive to this as it was designed 
>with 'digitally optimized' lenses in mind, and less compromised for the

>sake of older lenses which did not have their ray bundles as 
>perpendicular to the sensor array as the E-1's own lenses.
>This isn't very noticeable on my 20D and might not be that noticeable 
>on the R-D1 as the latter is definitely intended for 'non-optimized' 

B.D. wrote:
Keep in mind that Olympus long resisted the use of the old Zuiko lenses
on the E-1, and when they finally gave out an OM to E-1 adapter, they
listed the aperture range at which the lenses should be used - and not a
single lens was recommended for use at anywhere near the maximum F stop.
So it's hardly surprising that you're finding what you're finding.

That said, I've used the 50 1.2 on my E-1 - at 1.2 (why else would I use
it?) - turning it into a 100 f 1.2, and have gotten some surprisingly
good results. I also used the 21 f2.

Leica Users Group.
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In reply to: Message from pklein at (Peter Klein) ([Leica] RD-1 users: Light loss with fast lenses?)