Archived posting to the Leica Users Group, 2012/06/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]f4 is a ratio, it all depends on the actual focal lens. Add to this approximations when labelling, and engineering tolerance, plus the shape of the blades, etc. It all gets worse with a "crop" sensor I think ... the light distribution is not what the designers had anticipated. Just take the camera out and shoot my friend, the Nikon metering system will be your other friend ;-) Amiti?s Philippe Le 10 juin 12 ? 23:25, Aram Langhans a ?crit : > 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 >>> >>> >> >> >> > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information