Archived posting to the Leica Users Group, 2005/03/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I haven't notiticed this with my 35/1.4 Minolta lens on either my Maxxum 9 film camera nor my new Maxxum 7D DSLR. The 1.4 aperture appears to be "true". -dan c. At 12:27 PM 11-03-05 -0500, B. D. Colen 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. > >B. D. > >-----Original Message----- >From: lug-bounces+bdcolen=earthlink.net@leica-users.org >[mailto:lug-bounces+bdcolen=earthlink.net@leica-users.org] On Behalf Of >Henning Wulff >Sent: Friday, March 11, 2005 11:43 AM >To: Leica Users Group >Subject: Re: [Leica] RD-1 users: Light loss with fast lenses? > > >At 8:50 PM -0800 3/10/05, Peter Klein wrote: >>Folks: I've noticed an interesting phenomenon with my E-1 and fast >>OM Zuiko lenses, and I'm curious if something similar happens with >>RF lenses on the RD-1. >> >>The widest apertures don't give me as much light on the E-1 as they >>do on film. My 50/1.4 is more like a 50/1.8 wide open. My 50/1.8 is >>more like a 50/2. >> >>Note that I'm not talking about metering error here, nor am I >>talking about vignetting at the edges. I'm talking about using my >>50/1.4 to take a bunch of bracketed shots of a blank wall with >>manual exposure. If I get a pixel level of 128 near the image center >>at 1/30 at f/2.8, then I would expect to get the same level at 1/125 >>at f/1.4. But I don't. I need to slow the shutter to 1/80 to get >>the same shade of grey. This is 2/3 of a stop more exposure than >>expected. The same lens shows less than 1/3 stop loss with film. >> >>I'm curious if the RD-1 has a similar effect with f/2 and especially >>f/1.4 lenses. Could some of you RD-1 owners who have Summiluxes and >>Noktons check this out and let us know? >> >>I'm sure all this has to do with sensor angle of acceptance vs. lens >>characteristics like exit pupil size and angle of the cone of light. >>There has been some talk of this on digicam forums, with the usual >>indistinguishable combination of heat and light. I personally >>believe that something is indeed going on. I've seen too many >>examples of weird DSLR behavior with film lenses at maximum and >>minimum apertures. >> >>DSLR owners who have used the same fast lens on both a DSLR and film >>body, feel free to chime in, too. >> >>Thanks! >>--Peter > >Good to hear you're feeling better! > >Happens on film, too. If you ever try to be systematic on film, and >measure your exposures with a densitometer, you'll note the same >thing. The suspicion might come up that the manufacturers have >inflated their maximum f-stop numbers for the sake of marketing, but >due to the less than optimal diameters of lens elements, especially >fast ones (we're neither willing to pay for nor carry lenses with >optimal sizes) there is a lessening of effective, or T-stop for very >fast lenses. An f/1.4 lens will still be faster than an f/1.8, but >neither actually produces twice as much light on the film as the same >lens stopped down to f/2.8 resp. 3.5. Note that an f/1.4 lens stopped >down to f/2 will produce a denser neg than an f/2 lens wide open; but >you are carrying a much larger and more expensive 'f/2' lens in the >f/1.4 stopped down. > >The aperture marked on the lens is a geometric aperture, not a >transmission aperture, from whence comes the 'T-stop'. >--------------------------------------------------- > >I 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' >lenses. > >-- > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com >_______________________________________________ >Leica Users Group. >See http://leica-users.org/mailman/listinfo/lug for more information > >_______________________________________________ >Leica Users Group. >See http://leica-users.org/mailman/listinfo/lug for more information >