Using auto extension tube on standard lenses for macro purpose

[MEPER]

I received a 35mm auto extension tube for Z-mount.
I tried it on my Nikkor-Z 50/1.8 S.
The attached test image is shot with lens set to infinity and aperture 5.6.
It is very useable and I get less LO-CA with this lens as with AFS 105/2.8 Micro.
A downside is that subject distance is quite close.

Another downside I don't quite understand is that flash overexpose by almost 4 EV's. I set flash compensation to -3 (which is max).
The contacts on ext tube works fine as everything can be controlled and everything on display works. But camera seems not able to measure and set the correct light output for the flash (SB-910).
Without the ext tube and lens only it is fine. Also if I take an image at same distance to the subject. What could the reason be that camera is "fooled"?    in the old TTL-days it would work but not with iTTL?
It can probably be solved by switching to manual flash output (1/16, 1/32 etc.... mode). Or just use -3 EV and then the last EV in post processing. It was how the attached image was exposed.

[Birna Rørslett]

The Nikkor 50mm f/.8Z handles added extension pretty well. However, the working distance can be quite short so finding the perfect vantage point for a close-up can be tricky, plus getting the subject properly lit is a challenge. When all pieces in the puzzle clicks into position, very sharp images may result.

I have various extension tubes for  Z mount from makers Meike and Fotodiox. The former brand offers the slimmest tubes , whilst the latter by far has the better quality.

Subject is the fern Dryopteris affinis. Shot on a Scotland trip with Dave Patterson a few years back, at Skye.

[MEPER]

That is a nice and sharp picture!
It is a Fotodiox 35mm auto tube I have. Nice quality and also the anti reflex paint inside the tube is high quality.

I found out why my pictures got overexposed by the flash.
It was because the lens was set to infinity and the distance to subject only few cm. The same happens with lens alone if I set it to infinity and take a picture close up.
So flash exposure is not a "realtime" measurement. It seems to use the distance information. In this case the contacts on ext tube is a disadvantage?
To have just a "dumb" tube would have worked better then the camerabody was forced to used another method to control the flash?
It usually works with just an old MF lens.

With 35mm extension the 50/1.8 needs to be at infinity so have some distance to subject. So far it is the only Z-ext tube I have.

[Birna Rørslett]

I have Meike 11 and 15mm, and Fotodiox 18 and 35mm tubes.

[MEPER]

I will try to get the shorter Fotodiox tube. I don't Fotodiox for sale in DK. The 35mm I got from ebay from a German seller.
I tried the 35mm tube on the Nikkor-Z 24-70/4 S set to 70mm and infinity. Aperture set to 5.6.
I got a better result than expected. It could be useful for travel if the 24-70 was the only lens the the 35mm tube would nok take up a lot of space.
This time I set the flash output to 1/128 and compensated +0.55 EV in post.
Still strange the behavior if lens is set to infinity that TTL flash setting overexpose a lot. TTL flash would work better with a non-auto ext. tube.
This combination has also lesser LO-CA than AFS 105/2.8 micro.

[MEPER]

The cheap 50-250mm DX kit-lens is also very useable?
Lens on its own is quite good. A travel kit with 16-50, 50-250 and the ext tube and you can make a lot of nice pictures.
The attached test image is where lens it set to 250mm and full open aperture (6.3).
AF was used in this case and VR worked fine also. TTL-flash will still overexpose so it was set manually also in this case.
The distance to object is very decent and VR helps.