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Front focussing on A7rII and certain lenses

I have just done a very quick check with the new FW and the FE 35/1.4 in very low light. With the lens stopped down and using the back button AF I clearly see and hear that there is a first step in which the lens open up (not fully, probably just at f:2) to help focus and then closes again at the selected opening. I do not know if the complete AF routine or just the first step is performed with the lens wide open.
 

Viramati

Member
Did anybody check your low-light autofocus with the new firmware?

There's just been a report on DPReviews that low-light autofocus is degraded, at least with some lenses that previously showed focus shift and some non-native lenses.

There is speculation that this is because the A7RII aperture behavior that allowed focus shift (focus wide open, then stop down) has been changed, and that the new behavior allows less light onto the sensor during autofocus. In other words, camera aperture behavior is back to the previous A7 cameras. (Focus at taking aperture.) I can't vouch for this myself. Maybe a false alarm. But maybe worth checking?

--d
From how I see my FE24-70 is behaving this would make sense as the aperture iris now seems to stay stopped down when focussing. On the FE55 it still opens up fully. haven't tested the FE16-35. I guess they have had to fix it at the expense of low light focus speed if stopped down but personally I would be tending to shoot these lenses wide open in low light so performance should remain the same
 

Annna T

Active member
From how I see my FE24-70 is behaving this would make sense as the aperture iris now seems to stay stopped down when focussing. On the FE55 it still opens up fully. haven't tested the FE16-35. I guess they have had to fix it at the expense of low light focus speed if stopped down but personally I would be tending to shoot these lenses wide open in low light so performance should remain the same
There is a workaround for focusing problems in low light, which I use quite often with the A7r : I have ISO set to the four ways controller wheel, so it is just a small rotating move of the thumb to get much higher ISO, focus and then with a reverse move of the thumb you return to the wanted ISO.

I know that many don't like keeping something on that wheel, out of fear they could accidentally change their settings. But I rarely have that problem, so I keep it active and it is very handy for quick changes.
 

vjbelle

Well-known member
I have tested it today with a Spyder Lens cal target, specially made for this sort of exercise.


EDIT: I have to add that the more cameras and lenses I own and test, the more I realise that one can only ever speak for a particular copy of a lens on a particular copy of a camera. YMMV.
OMG...... how true!!:salute:
 
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