Archived posting to the Leica Users Group, 2012/06/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I have more questions than answers as to why this is even so. I need to adapt more lenses to see what is happening. My 100 APO is adapted, but I did not use it. I want to try an f2, f2.8, f4, f5.6 (I don't have) primes or zooms wide open and see how the match up with a Nikon at those f-stops. >From my field experience, all three of my lenses when used wide open give what I would consider perfect exposure, even though the data from my test seems to suggest the zoom is underexposing up to 1 stop. Ignoring that, one question is, why does an f/4 lens wide open meter the same as an f/2 lens wide open (correct exposure that is)? And then, why does the f/2 lens when stopped down to f/4 not behave like an f/4 lens wide open? How the heck does the meter know that you have stopped a lens down vs a lens with the same aperture wide open? F4 should be F/4 on any manual lens, letting the same intensity of light through. Is it something to do with the angle of light rays? Maybe wide open they all have about the same angle of light from a given point in the field, but as you stop down the angle changes? I am just thinking out loud. Aram -------------------------------------------------- From: "Jim Nichols" <jhnichols at lighttube.net> Sent: Sunday, June 10, 2012 12:45 PM To: "Leica Users Group" <lug at leica-users.org> Subject: Re: [Leica] Using M (and R) glass on a Sony NEX-7 Now DATA > Aram, > > I will add to the confusion. > > After plotting your data on the NEX-7, I became curious about my Olympus > E-1, which is an early professional model. I compared the companion lens, > which was the Olympus 14-54 zoom, to my Summicron-R and my Elmarit-R 60mm > Macro. By some stroke of luck, I was able to use a log scale for this > one, which helps with the comparison. I have tried to do the same for my > first chart of your data, but can't find that option again. > > If the 14-54 lens, which communicates with the camera, is taken as the > "standard", then my Elmarit-60 is not too far off this line. However, my > sample of the Summacron-R 50mm shows that it departs from the norm, > particularly above f/8. In your data, this departure starts at about > f/5.6. After seeing this, I would not choose the Summicron-R as a measure > of performance for a Leica prime lens. My Elmarit-R 60 looks much better. > > In looking at your data for the Leica zoom, I begin to wonder if there are > too many compromises in zoom lens design. I did not pursue recording the > 14-54 data at other focal lengths. > > Jim Nichols > Tullahoma, TN USA > ----- Original Message ----- > From: "Aram Langhans" <leica_r8 at hotmail.com> > To: "Leica Users Group" <lug at leica-users.org> > Sent: Sunday, June 10, 2012 11:00 AM > Subject: Re: [Leica] Using M (and R) glass on a Sony NEX-7 Now DATA > > >> That's what I mean, too, except the Nikon D7000 and D300 does not behave >> the same as Howard's D700. >> >> Can anyone make sense of these data? >> >> Lens 1 is Nikon 50/1.2 >> Lens 2 is Leica-R 50/2 Summicron >> Lens 3a is Leica-r 35-70/4 shot at 35mm >> Lens 3b is same lens shot at 50mm >> Lens 3c is same lens shot at 70mm >> >> Subject, an evenly lit patch of grass in my front lawn. Went through the >> f-stops twice for each lens to check consistency. Same reading each >> time. >> >> >> f-stop Lens 1 Lens 2 Lens 3a Lens 3b >> Lens 3c >> 2 1600 1600 >> 2.8 800 1000 >> 4 400 400 640 500 640 >> 5.6 200 100 160 200 320 >> 8 100 40 50 60 100 >> 11 50 25 30 30 50 >> 16 25 15 20 20 20 >> >> As you can see, the Nikon behaves as it should be and meters correctly >> through the f-stop range, halving the shutter speed for each smaller >> f-stop. >> The Leica lenses do not and progressively overexpose as you stop the lens >> down. I am surprised that the zoom did not meter correctly wide open. >> In my field experience, wide open is not a problem, and the overexposure >> only starts to show up as you stop down. >> >> I am also surprised that the overexposure is limited to about one stop. >> In my field experience I sometimes have to compensate about 2 stops. >> >> That said, there is about a one stop overexposure in this test while my >> Canon, when I had it, would overexpose about 4 stops if you stopped down >> enough. >> >> >> >> >> -------------------------------------------------- >> From: "H&E Cummer" <cummer at netvigator.com> >> Sent: Sunday, June 10, 2012 6:04 AM >> To: <lug at leica-users.org> >> Subject: [Leica] Using M (and R) glass on a Sony NEX-7 >> >>> >>> Date: Sat, 9 Jun 2012 16:13:38 -0600 >>> From: Bill Nelsch <photobynelsch at gmail.com> >>> Subject: Re: [Leica] Using M (and R) glass on a Sony NEX-7 >>> To: Leica Users Group <lug at leica-users.org> >>> >>> I have a stupid question: When you say the D7000 is "linear" - what >>> does >>> that mean actually? How does that affect the exposure? >>> >>> Bill in Denver >>> >>> Hi Bill, >>> By linear I mean that as you close down the lens aperture the shutter >>> speed drops by an equal amount in terms of light transmission >>> If you are at f5.6 and 1/500 and then close down to f8.0 the shutter >>> speed adjusts to 1/250 - to f11.0 the shutter speed drops to 1/125 >>> keeping the light transmission the same. That's what happens on the >>> Nikon. On the Canon without Canon lenses that "talk" to the body >>> as you close down a Leica R lens mounted with an adapter that isn't >>> chipped the shutter speeds drift away from the above response and you >>> get more and more exposure variation. >>> Hope this clarifies my point for you. >>> Cheers >>> Howard >>> >>> >>> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information >> >> > > > >