my recent experimentation with the FLE on my contax has emboldened me to examine the FLE settings on my various other lenses. today i looked at my MD 24/2.8 and MD 28/2. seems like the 28mm was almost dead on but the 24mm was a ways off. i readjusted it and now have a much flatter field and better corner performance. i need to reshoot my infinity test series again...
sebboh wrote:
my recent experimentation with the FLE on my contax has emboldened me to examine the FLE settings on my various other lenses. today i looked at my MD 24/2.8 and MD 28/2. seems like the 28mm was almost dead on but the 24mm was a ways off. i readjusted it and now have a much flatter field and better corner performance. i need to reshoot my infinity test series again...
How do you adjust it?
Field curvature is a serious issue with my loaner copy (MC) as well.
Phillip Reeve wrote:
How do you adjust it?
Field curvature is a serious issue with my loaner copy (MC) as well.
i'm sure it's different between the MC version and my plain MD, but on mine you remove the rubber on the focus ring and the tape under it and there are two parts to underlying focus ring. after loosening some set screws you can move them separately to adjust the relative positions of the two moving groups.
is you adapter shimmed for infinity? if not that could be exacerbating FC issues.
A SOOC (except for reducing highlights and modest lighten up the shadows) 35/1.8 at f/2.8 I think. A processed and cropped version is on the A7 images thread.
Elaborating on the A7/r/s thread. I am a bit dissapointed with the performance of my MD Rokkor 24/2.8 on the A7r. Although the scene below is not the ideal with this lens I had expected it to perform a bit better.
Two examples, one wide open, one at f/11.0, the focus is on the trees. Although difficult to see in these downsized pictures in both cases the trees are not very sharp. Not a dealbreaker. More problematic are the corners and in fact the whole zone around the centre of the image with lots of smearing and fringing (bleu, green and magenta) probably, if my understanding is correct, due to field curvature.
While the Rokkor was not perfect on the NEX5N, the resulting images generally were a pleasure to look at. With the A7r the behaviour is quite unpredictable (to me - but I have little understanding on lenses and what I know is from this forum ). Worse, I just do not like the images the lens produces.
For close up and near by centre focus the situation is different, but the versatality of the lens seems to be gone with the switch from NEX5N to A7r.
Basso wrote:
Elaborating on the A7/r/s thread. I am a bit dissapointed with the performance of my MD Rokkor 24/2.8 on the A7r. Although the scene below is not the ideal with this lens I had expected it to perform a bit better.
Two examples, one wide open, one at f/11.0, the focus is on the trees. Although difficult to see in these downsized pictures in both cases the trees are not very sharp. Not a dealbreaker. More problematic are the corners and in fact the whole zone around the centre of the image with lots of smearing and fringing (bleu, green and magenta) probably, if my understanding is correct, due to field curvature.
While the Rokkor was not perfect on the NEX5N, the resulting images generally were a pleasure to look at. With the A7r the behaviour is quite unpredictable (to me - but I have little understanding on lenses and what I know is from this forum ). Worse, I just do not like the images the lens produces.
For close up and near by centre focus the situation is different, but the versatality of the lens seems to be gone with the switch from NEX5N to A7r. ...Show more →
it's difficult to assess your lens without seeing full sized images. here's how mine performs after recalibrating the FLE.
whole frame (adobe defaults + CA correction): http://farm8.staticflickr.com/7638/16307295963_5b348de3be_o.jpg
crops: http://farm8.staticflickr.com/7618/16304950904_f219d7a54a_o.jpg
i should have made the crops a little bigger, the corner weakness really only covers that corner crop and things are pretty good as soon as you move in from that. i would say that the performance is acceptable wide open all the way to the outer midzone. overall the infinity performance does not seem near as good a performance at 3m or closer.
it seems like there must be some focus shift or the lens is heavily effected by diffraction since the midzone seems sharper at f/4 than smaller apertures. the lens also seems very sensitive to focus location – down seems increase dof towards the camera without expanding dof away from the camera as much as i would expect.
That looks noticeably better than what I experienced with a MD Rokkor 2.8/24. I used a novoflex adapter for that but it is not adjusted for infinity focus so this could increase field curvature.
Phillip Reeve wrote:
That looks noticeably better than what I experienced with a MD Rokkor 2.8/24. I used a novoflex adapter for that but it is not adjusted for infinity focus so this could increase field curvature.
Basso wrote:
To continue on the 24/2.8. To illustrate the performance of my 24/2.8 at infinity here a few 100% crops of the @ f/11.0 in the port above.
(sorry for presenting in this way. Have to improve my PS skills)
that looks terrible. it could be that your floating element is incorrectly placed, your adapter is too short or crooked, or there's something wrong with the lens. is yours the 55mm filter thread version or the 49mm filter thread version like mine?
mine is definitely worse at infinity than close up, but not near that bad.
here is the full sized version of a relatively close focused shot at f/11.
sebboh wrote:
that looks terrible. it could be that your floating element is incorrectly placed, your adapter is too short or crooked, or there's something wrong with the lens. is yours the 55mm filter thread version or the 49mm filter thread version like mine?
mine is definitely worse at infinity than close up, but not near that bad.
here is the full sized version of a relatively close focused shot at f/11.
Well, yours do look better thats clear. For me it is hard to understand its bad performance in the infinity shot and at the same time the quite remarkable performance in the near focus shot that I posted above (taken within hours of each other). If something is misaligned would then the near focus shot turn out as good as this one? Well anyway, I have the 55mm version and a Novoflex adapter that works flawlessly for all my Rokkors (except for certain angles towards a lightsource when it can produce flare).
Maybe I should put the lens through a more systematic test than the one showed here (at the middle of a Summer day with the sun coming from the left), as the sunlight may have influenced the performance by producing flare or related things, which can be an issue with these lenses as you and Phillip observe above. Anyway, thanks for commenting
). Worse, I just do not like the images the lens produces. 
