Andrew Gough wrote:
Charles, this is caused by the adapter bring slightly too short. I would shim the adapter.
Andrew
Thanks Andrew I was thinking the same, but then my calibration for the focus dot confirmation may also move which is very accurate for near to medium distances. Ideally a VM-E style adapter would be perfect where you can vary the tolerance to suit.
This morning I received my Leitax mount and it was focusing closer to infinity as per the mark on the R 50 Cron. The only issue is that my D850 focus confirmation dot was now back focusing at close to medium distances while it was fairly accurate at far distances.
I have reverted back to using the Fotodiox adapter as the focus confirmation is very accurate for close to medium distances and I know the mark on the lens for far to infinity which I will manually set or just use LV.
Is there a way to adjust this non linearity? I suspect not but I thought I might ask the question here
Hi, Charles,
I don’t have experience to test multiple lens adapter with the same lens. But it surprise me that you find it changed confirmation results. I would expect AF engine should see focused image the same even with flange distance change because of adapter.
I don’t eliminate the possibility that slightly different flange distance will degrade lens performance, but generally speaking, R lens are less sensitive because of SLR nature and mostly older design without float system.
Before you draw conclusion, maybe more through test by picking better defined focus target?
I really hope it can work out for you as your R images have been super. and shooting manual can be fun.
charles.K wrote:
This morning I received my Leitax mount and it was focusing closer to infinity as per the mark on the R 50 Cron. The only issue is that my D850 focus confirmation dot was now back focusing at close to medium distances while it was fairly accurate at far distances.
I have reverted back to using the Fotodiox adapter as the focus confirmation is very accurate for close to medium distances and I know the mark on the lens for far to infinity which I will manually set or just use LV.
Is there a way to adjust this non linearity? I suspect not but I thought I might ask the question here ...Show more →
This is what I also thought. But I used a lens align target and with the leitax adapter it was back focusing about 6 to 8 cms at close to medium distances. For close to infinity it was quite accurate.
Wheres with the Fotodiox adapter it is very accurate for near to medium with the focus confirmation and I just need to set the focus manually for far/infinity. There is a definite non linearity at infinity. I have often had my Leica M lenses readjusted for this non linearity at Camera Clinic in Melbourne.
I have another Fotodiox adapter as I might try this also. It is hard to measure the depth with the flange protruding with a vernier. The IQ with the Fotodiox is excellent so I am trying to figure this out particularly how it relates to the D850 focus confirmation. I suspect there is a focusing curve/line that is appropriate for Nikon lenses for the focus confirmation dot and if another lens is non CPU even though it has been entered in manually cannot be changed. This is the only thing I can think off
zhangyue wrote:
Hi, Charles,
I don’t have experience to test multiple lens adapter with the same lens. But it surprise me that you find it changed confirmation results. I would expect AF engine should see focused image the same even with flange distance change because of adapter.
I don’t eliminate the possibility that slightly different flange distance will degrade lens performance, but generally speaking, R lens are less sensitive because of SLR nature and mostly older design without float system.
Before you draw conclusion, maybe more through test by picking better defined focus target?
I really hope it can work out for you as your R images have been super. and shooting manual can be fun.
Does your adapter have a chip on it? If it does, what focal length is it set to?
Andrew
Hi Andrew. I do have a dandelion chip, but my understanding is that is does not work with the later Nikon's or interferes. The lens is entered in manually as a non-CPU lens with both f/2 and 50mm and is then saved within the menu. So technically there is no need for the chip.
I would be using the 50 Cron R for mainly portraits and for landscapes I just use the present mark on the lens so it is excellent in this respect
In this lens the entire block of optics moves to provide focus, so this is very unusual behaviour. You might want to do a manual focus check on a reference Nikon lens, as it could be the AF system is slightly out.
In this lens the entire block of optics moves to provide focus, so this is very unusual behaviour. You might want to do a manual focus check on a reference Nikon lens, as it could be the AF system is slightly out.
Andrew
Hi Andrew,
Great shots!!!
Yes I agree it is unusual. I have my 105/E and 70-200E and these lenses are very accurate throughout the range with no fine tune AF correction. In effect the 50 Cron R lens is fine for near to medium and just front focusing at far/infinity. I have corrected a few Art lenses with similar characteristics on the D750/D810 and now D850.
As I mentioned this is not an issue as the near to medium is very accurate and sharp for portraits. For landscapes I use more the LV anyway.
Andrew Gough wrote:
Thanks Charles. I was not aware that you had had this problem with other lenses. Perhaps Nikons AF does a rough acquisition and then fine tunes...
The D850 AF is very fast and accurate but with PDAF off sensor the camera needs to assume a calibration profile which works 99% of the time. With Art lenses since they are third party generic lens mounts and this is why the need for the USB dock for Canon and Nikon as it tweaks non linear profiles or quirks in the optics.
I was thinking the same, but then my calibration for the focus dot confirmation may also move which is very accurate for near to medium distances. Ideally a VM-E style adapter would be perfect where you can vary the tolerance to suit.
