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+--- Thread: Light loss: Why do similar lenses exhibit such a big difference? (/showthread.php?tid=3786)
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Light loss: Why do similar lenses exhibit such a big difference? - Rainer - 07-22-2010
Just regarding the metering differences between the same body metering with an EF lens
and metering with an MF lens (with no electrical coupling)...
Make a test ... put an EF lens on the body select wide open aperture ... focus on a scene,
disengage AF (just to have a comparable and reproducable starting point) ... now
meter with the different metering modes (matrix, partitial ... spot) ... and then ...
unlock the lens and screw it a few degrees as if you would like to take it of the body ...
just enough that the electrical coupling no longer works ( the body will now show f/00)
... it now behaves like an MF lens ... but it is absolutely the same lens that you had used
before ... meter again with the same modes as before ....
with my 50L I get up to 1.5 stops difference depending on metering mode.
Light loss: Why do similar lenses exhibit such a big difference? - Yakim - 07-23-2010
Update: I re-tested and took pictures. You wouldn't be surprised if I told you shutter speeds are the same, right?
Rainer, I'll try it. You got me curious.
Light loss: Why do similar lenses exhibit such a big difference? - wim - 07-23-2010
[quote name='Yakim' date='23 July 2010 - 11:44 AM' timestamp='1279878275' post='1249']
Update: I re-tested and took pictures. You wouldn't be surprised if I told you shutter speeds are the same, right?
Rainer, I'll try it. You got me curious.
[/quote]
Interesting, those shutter speeds being the same. I really wonder now what was going on in your test....
Kind regards, Wim
Light loss: Why do similar lenses exhibit such a big difference? - Yakim - 07-23-2010
Unfortunately it's a no-go. Exposure was exactly the same in all 6 options - 1/350. What's more, the pictures and histograms were also the identical. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />Lens used was the 100/2.8 IS.
Happy shooting,
Yakim.
Light loss: Why do similar lenses exhibit such a big difference? - allanmb - 07-23-2010
So are you saying that you get no light loss any more? I would expect light loss as the way most macro lenses work is to incerase the distance of the elements from the sensor - similar to adding extension tubes. This naturally causes light loss so I'd be surprise if a lens maintains the same exposure at infinity and 1:1
Light loss: Why do similar lenses exhibit such a big difference? - Yakim - 07-23-2010
[quote name='allanmb' date='23 July 2010 - 04:35 PM' timestamp='1279899327' post='1261']
So are you saying that you get no light loss any more? I would expect light loss as the way most macro lenses work is to incerase the distance of the elements from the sensor - similar to adding extension tubes. This naturally causes light loss so I'd be surprise if a lens maintains the same exposure at infinity and 1:1[/quote]
No. That's not what I'm saying. The last test had nothing to do with light loss at all. I just wanted to see if the communication issue has any effect on exposure. Rainer's experience seem to corroborate it. Mine does not.
Light loss: Why do similar lenses exhibit such a big difference? - joachim - 07-24-2010
[quote name='Yakim' date='23 July 2010 - 03:06 PM' timestamp='1279890397' post='1256']
Unfortunately it's a no-go. Exposure was exactly the same in all 6 options - 1/350. What's more, the pictures and histograms were also the identical. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />Lens used was the 100/2.8 IS.
Happy shooting,
Yakim.
[/quote]
Hi Yakim,
I am sorry, but you just lost me on what you tested since your original test.
Ta
Joachim
Light loss: Why do similar lenses exhibit such a big difference? - Yakim - 07-24-2010
I was testing what Rainer suggested.