Contax G Biogon 28mm 2.8 black strip @high shutter speeds

[felixeter]

Hey all,

Question - I have been using the Techart Golden Eagle (the one mentioned here) https://chadwadsworth.com/2015/08/30/913/ to adapt my wonderful Contax G lenses to my A7RII. It's been a year that has had a few quirks, but mostly problem free.

I most often use the 90, but sometimes the 28. Besides the smearing that has been talked about sometimes, and that I haven't found to be too big a deal, I was recently on a shoot in bright sun and was shooting at speeds of 1/4000 to 1/8000 and noticed the bottom of the frame wasn't getting exposure - almost like pushing a flash sync too far but I wasn't using flash. 

 

Does anyone have any idea why this might be?

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here's 1/8000

here's 1/5000

here's 1/4000 (fading more - problem is minor)

here's 1/3200 (seems to no longer be an issue)

 

I've been able to replicate this issue - has anyone else had this or similar issue with the Contax/Techart set up or any other lenses? Is this a wide angle thing? I can live with it if I can only shoot up to 1/3200 with this lens as I don't use it a ton, but I haven't had it with the 90 as far as I know, I've shot with that lens a lot in all conditions. Just curious what's going on.

 

[favol84]

It's not lens related. just avoid electronic first shutter curtain with fast exposure times. That's all.

 

https://phillipreeve.net/blog/limitations-of-the-electronic-shutter-function/

[felixeter]

Interesting!

I forget why I had it turned on in the first place. But I turned it off and indeed it went away.

 

BUT!

I don't have this issue with the 55 1.8 mounted though, or with the 90mm Sonnar 2.8. Any idea why that might be? I just double checked with EFCS on, and reshot with those other lenses and the issue only shows up on the 28. Maybe it affects wide angle lenses differently for some reason?

 

Thanks for the information.

[favol84]

28mm is a wide angle. Using another wide angle would reproduce the issue (the wider is the lens, the worst is the effect ).

[felixeter]

28mm is a wide angle. Using another wide angle would reproduce the issue (the wider is the lens, the worst is the effect ).

I know it's a wide angle. I was trying to figure out if it was an effect to do with wide angle lenses exclusively. The fact that you said it wasn't lens related in your prior post confused me. It's not lens related in the sense that it's not specific to this particular lens (the 28mm 2.8 Biogon) but it is in the sense that the problem doesn't happen with normal or telephoto lenses.

[Username]

Right. Lens-type related, but not lens specific.  

   

It happens with Biogons, Super Angulons, etc,  

but usually not Distagons, Flektogons, or other 

retrofocus designs. Lens-TYPE is the deal. 

[felixeter]

Got it - thank you! 

[Zé De Boni]

28mm is a wide angle. Using another wide angle would reproduce the issue (the wider is the lens, the worst is the effect ).

 

Truly, I don't understand why this issue is related to lens angle. I discovered the problem (which I had always theoretically suspected) shooting the sun (Venus transit 2012) with a 500mm + 2x Conveter on an A77 camera (+13 stop ND filters). I tried the electronic first courtain shutter to minimize camera shake, but soon I had to go back to the conventional shutter. Back to editing, the images taken with the first courtain electronic shutter could be just fairly corrected with a gradient filter in LR. But that was rather a high contrast image of the Sun disk against a black background.

[Landru]

Yes.  I have seen exactly this problem with the A7ii/Techart Golden Eagle/Contax G 28mm lens combination.  Does not occur on the 45 or 90mm lenses, nor with the 28 at shutter speeds of about 1/3200 or faster.

 

Why does this happen only with a wide angle? I don't know.  Perhaps a firmware bug where electronic shutter, auto-ISO, and on-sensor VR do not play well together.

 

Overall, it's been great to use the G lenses again.  Compact primes, autofocus, and cheap (especially if you already own them) make a nice complement to the A7 body.

[felixeter]

Yes.  I have seen exactly this problem with the A7ii/Techart Golden Eagle/Contax G 28mm lens combination.  Does not occur on the 45 or 90mm lenses, nor with the 28 at shutter speeds of about 1/3200 or faster.

 

Why does this happen only with a wide angle? I don't know.  Perhaps a firmware bug where electronic shutter, auto-ISO, and on-sensor VR do not play well together.

 

Overall, it's been great to use the G lenses again.  Compact primes, autofocus, and cheap (especially if you already own them) make a nice complement to the A7 body.

I did not have auto ISO on when this problem occurred for me, FWIW. Turning off EFCS worked for me. But yes, I agree that as a whole the G2 lenses are great on the A7 series - though, if you see the issue I've had with my 45 in the other thread at this point the 90 has been the only lens that hasn't been 'quirky' in some respect for me. I use the 90 the most by far, so I'm not too frustrated by it. But I would like to use the 45 more without worry.