Phase One DF exposure meter problems with manual lenses

[elvispreasley]

I just changed my old good Mamiya AFD on more modern and "fresh" Phase One DF body, but found one interesting problem: it seems like exposure meter of the camera is going crazy if I'll stop down an aperture of the lens greater then f5.6.
I have to admit, that I'm using DF with P25 digital back and Mamiya Sekor manual lenses only (Mamiya Type C focusing screen is also installed in the camera body) so I guess this issue is related to the case - how DF exposure meter works with old manual lenses.
I've read already an article from Phase One, which says that exposure meter of the DF+ and XF cameras was simply designed for working with modern "digital" lenses and with manual lenses it can give wrong value. To compensate this issue there was suggestion - to set an exposure compensation value to +2.0. However, in case with my DF (by default) to get right exposure with my Sekor lenses, I have to set exposure compensation value to -1.7. It works good like that, until I'm stopping down the lens greater then f5.6 - in this case the image starts to be very underexposed, so to bring the proper exposure back - I need to set the exposure compensation value to +1.0. But after some short time an exposure goes to its previous condition, so I have to set -1.7 again.
Anyone else ever had this problem? Is there any solution (change some custom settings on DF body) to solve it?

[E.J. Peiker]

I have a Mamiya Sekor 45mm f/2.8 manual lens and when I use that on the Phase One XF camera body, a correct exposure reads -5 on the exposure meter.  In other words if I use a new AF lens and set the exposure to zero on the meter for a "correct" exposure and I then mount the manual lens and set the identical exposure, the meter shows -5...  I've just gotten used to this.  In any case, I don't think your problem is unique

[elvispreasley]

I have a Mamiya Sekor 45mm f/2.8 manual lens and when I use that on the Phase One XF camera body, a correct exposure reads -5 on the exposure meter.  In other words if I use a new AF lens and set the exposure to zero on the meter for a "correct" exposure and I then mount the manual lens and set the identical exposure, the meter shows -5...  I've just gotten used to this.  In any case, I don't think your problem is unique

Thank you for your reply, E.J.
I also don't really think, that my problem is unique, but it's definitely different then you have) Besides the thing that in normal condition - to get a right exposure, I need to set exposure compensation to -1.7, this value is "jumping" occasionally from -1.7 to +1.0 and this is what I'm trying to resolve.
Also I'm not 100% sure that this spontaneous exposure change is depend of an aperture value, as I wrote before. It seems like, but I need to experiment a little more with it - to be sure.
However, I really hope, that this issue might be resolved by changing some custom settings in the DF camera body. My firmware version is 1.59, so the latest one, btw.

p.s: I also have Sekor 45mm 2.8, what I'm using on DF with P25 back. Love it a lot)

[Alexey.Danilchenko]

I have a Mamiya Sekor 45mm f/2.8 manual lens and when I use that on the Phase One XF camera body, a correct exposure reads -5 on the exposure meter.  In other words if I use a new AF lens and set the exposure to zero on the meter for a "correct" exposure and I then mount the manual lens and set the identical exposure, the meter shows -5...  I've just gotten used to this.  In any case, I don't think your problem is unique

It's more than not unique - it's commonly inconsistent. The exposure in A mode is unpredictable with manual lenses starting with DF cameras and up. I am not sure if that relates somewhat to the fact that it spot metering only and perhaps Type C manual focusing screen affects the meter. What I don't understand is why exposure metering needed such an "improvement" - it was working without any troubles on AFD, AFD II/III.

[E.J. Peiker]

It's more than not unique - it's commonly inconsistent. The exposure in A mode is unpredictable with manual lenses starting with DF cameras and up. I am not sure if that relates somewhat to the fact that it spot metering only and perhaps Type C manual focusing screen affects the meter. What I don't understand is why exposure metering needed such an "improvement" - it was working without any troubles on AFD, AFD II/III.

I shoot 100% in manual exposure mode and am simply talking about a meter reading that gives an equivalent exposure to a zero meter reading with one of the modern lenses when shooting the same scene.  All of my normal AF LS lenses meter consistently with each other for the same end exposure, it's just when I use that old Mamiya Sekor lens.

[Alexey.Danilchenko]

I shoot 100% in manual exposure mode and am simply talking about a meter reading that gives an equivalent exposure to a zero meter reading with one of the modern lenses when shooting the same scene.  All of my normal AF LS lenses meter consistently with each other for the same end exposure, it's just when I use that old Mamiya Sekor lens.

Point taken, I should correct myself - old manual lenses without any electrical contacts. But those work fine (with the limitation of spotmetering only) on all pre-DF bodies.

[E.J. Peiker]

Point taken, I should correct myself - old manual lenses without any electrical contacts. But those work fine (with the limitation of spotmetering only) on all pre-DF bodies.

They work fine on the XF too (after a slight modification to the lens mount).  I just take a test shot with the meter set to -5, check out the histo, make any adjustments if necessary and I'm good to go

[Alexey.Danilchenko]

They work fine on the XF too (after a slight modification to the lens mount).  I just take a test shot with the meter set to -5, check out the histo, make any adjustments if necessary and I'm good to go

The -5 ev correction hardly seems fine as a generic rule .  It means exposure meter i useless on those lenses. On AFD bodies spotmetering works just fine without  -5 or other esoteric corrections.