07-22-2010, 04:34 PM
[quote name='Yakim' date='22 July 2010 - 06:00 PM' timestamp='1279814405' post='1243']
So why does my test not corroborating this?
[/quote]
There may be a bunch of factors causing this. One of the reasons why I suggest you set up a completely controllable environment, and do take photographs as well.
Mathematically there si exactly 2 stops between infinity and 1:1, provided everything else stays the same. Since it doesn't, soemthing else must be causing this effect.
Well, I am sorry but the AOV certainly can have an influence on this. If you have a dark object in the centre, and a bright background, that may make a difference. Or the other way around for that matter. The effect of perspective may play a role, because the images aren't exactly the same. Especially not at 1:1 (Canon: FL 70 mm, Mamiya: still 120 mm). And you are comparing two different lenses here, and one of those on a camera it doesn 't really belong on. There could be many factors IOW which could affect this, and it likely does.
The problem is I don't really know, because I don't know your setup at all, of the testing grounds so to speak.
Ok, something is at play, and the only way to find out is make sure all variables are eliminated except one. Which means setting up a testing environment indoors, with controlled lighting, test all metering modes, too, and take photographs.
I have used many MF lenses, and they all metered differently, at different f-stops (closing the lens down manually). After a while you get to know the lenses, so I didn't really care too much about this. I do know. I also know that my C/Y 50 F/1.4 overexposes by more than 1 stop wide open on my Canon bodies, and is accurate from F/2.8, +/- 1/3 of an f-stop. What causes that I don't know. Personally, I took it as a given. Similarly, my Leitz-R 60 Macro. It underexposes at any f-stop, from about a 1/2 wide open to 1/3 at the others.
Kind regards, Wim
So why does my test not corroborating this?
[/quote]
There may be a bunch of factors causing this. One of the reasons why I suggest you set up a completely controllable environment, and do take photographs as well.
Mathematically there si exactly 2 stops between infinity and 1:1, provided everything else stays the same. Since it doesn't, soemthing else must be causing this effect.
Quote:1. 7D spot metering is 2.3%.
2. The link mentions nothing about lens design (IF or non-IF) so I conclude it is not a factor.
Well, I am sorry but the AOV certainly can have an influence on this. If you have a dark object in the centre, and a bright background, that may make a difference. Or the other way around for that matter. The effect of perspective may play a role, because the images aren't exactly the same. Especially not at 1:1 (Canon: FL 70 mm, Mamiya: still 120 mm). And you are comparing two different lenses here, and one of those on a camera it doesn 't really belong on. There could be many factors IOW which could affect this, and it likely does.
The problem is I don't really know, because I don't know your setup at all, of the testing grounds so to speak.
Quote:Exactly. The Mamiya was metered wide open. I did not change the aperure in it.
It took me a minute or so to change lenses and meter. Light levels did not change. I was so amazed that I did it again several minutes later. Same results.
Ok, something is at play, and the only way to find out is make sure all variables are eliminated except one. Which means setting up a testing environment indoors, with controlled lighting, test all metering modes, too, and take photographs.
I have used many MF lenses, and they all metered differently, at different f-stops (closing the lens down manually). After a while you get to know the lenses, so I didn't really care too much about this. I do know. I also know that my C/Y 50 F/1.4 overexposes by more than 1 stop wide open on my Canon bodies, and is accurate from F/2.8, +/- 1/3 of an f-stop. What causes that I don't know. Personally, I took it as a given. Similarly, my Leitz-R 60 Macro. It underexposes at any f-stop, from about a 1/2 wide open to 1/3 at the others.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....