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Minolta 50mm AF 1.4 - too dark at fully open?

Started Sep 9, 2017 | Discussions thread
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frdvdv Regular Member • Posts: 250
Minolta 50mm AF 1.4 - too dark at fully open?

Hi, I recently got an old, but in very good shape, Minolta 50mm AF 1.4 lens (red AF mark, yellow feet indication) (sn 1036335) for my Konica Minolta 5D (to replace my broken F1.7). I have some more 'old' Minolta AF lenses from the analogue era.

It works fine, and pictures are great, but one thing bothers me.

At fully open (F1.4) - shots are a bit darker then at (F2.0) with a similar exposure.

I optically checked the diaphragm blades, and they are fully recessed in the body at 1.4

I did numerous test shots (on manual) with the same exposure, like

f1.4 1/250
f2.0 1/125
f2.8 1/60
f4.0 1/30

and every time the f1.4 is about a 1/2 stop to a 1/3 stop darker then the f2. I tried it in darker and lighter situations, and also did numerous repeats on for ex F2 to see if the exposure was consistent, which it was.

When I do a shot on the 50mm at F5.6, exposure is identical to my (old Minolta 28-85 F3.5-4.5 AF zoom lens) on 50mm zoom with F5.6 and the same shutter speed.

Practically it won't be such an issue, since F2.0 or F2.8 works better with the portraits and shots that I tried, but it still surprised me that the F1.4 isn't really F1.4 but more F1.6 or F1.7

Is this 'normal' for this lens or am I missing something here?

Thanks,

Fred

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