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Schneider 43XL sharpness

G

gazwas

Active member
Just received my P65+, Arca M-line 2 and Schneider 43XL. Only done a coulpe of getting to know the camera shots and noticed that if I nail the focus in the centre of the image the edge of the image looked to me as it shifts focus. So, for the first time in my photographic life I decided to do the brick wall test...... YAWN :sleep006: ...... sorry!

Camera levelled with spirit level and each standard checked. Original image centre is sharp but the top roof section is not sharp but the wall behind this is sharp(er). In order to eliminate camera and digi back, I rotated the lens 90 degrees and shot again. Hay presto, centre sharp and top roof section sharp.

Can someone help and explain what going on or a test to let me short out if I have a lens/camera/back or user problem.

Hope everything becomes obvious when you see the attached.

Thanks, Gareth
 
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J

Jim2

Guest
hmm on the original, the bricks above the roof are sharper. When rotating the lens fixed the focus... wouldn't you think that the lens mount needs to be 'shimmed' somehow?
 
J

Jim2

Guest
PS I'm curious as to how you are doing the focusing? Did you look through the ground glass to focus?
 
yaya

yaya

Active member
One of the trade-offs for having such a large image circle is called field curvature, which makes the plane of focus look more like a bowl than a plane and sometimes it is not 100% symmetrical. It could be that this is what you are seeing.

But I'd call Arca as they surely know more than I do about the M !
 
G

gazwas

Active member
yaya said:
One of the trade-offs for having such a large image circle is called field curvature, which makes the plane of focus look more like a bowl than a plane and sometimes it is not 100% symmetrical. It could be that this is what you are seeing.

But I'd call Arca as they surely know more than I do about the M !
Click to expand...
Think you might be right Yair. I was pixel peeping and at normal print sizes you probably would not see this. Did some further testing tethered to a laptop and it looks more like user error than lens/camera problem. What looks initially sharp in the centre can be tweaked further to become frighteningly sharp with a tiny additional focus adjustment and everything pops into focus.

When you look at the MTF's on Schneider's site the charts also seem to suggest a sharpness fall off at the edge and by tweaking the focus seems to find a sweet spot to correct some of the possible field curvature.

Critical focus on the P65+ is very, very critical :eek:

Jim2 said:
You did one heck of a fine job! I'm impressed. Do you use a loupe / magnifier? What's the strength?
Click to expand...
Use a 4x loupe to focus which is fine for close ups but for wide angle photography its not powerful enough and am thinking of getting a Silvestri 8x lupe to help with wide shots.
 
dchew

dchew

Well-known member
Gareth,
I've also been playing with my new 43xl (on an Alpa STC). I agree there is definitely a critical sweet spot. I see it every time I go through the shimming exercise on the Alpa w/ HPF rings. I can tell the difference between 12.9 and 13.7 feet. And that's on a 43mm. You should see how sensitive the 100HR is! I'm getting a Leica Disto...

By the way, have you shifted much? Nasty color cast on mine w/ a P65+. Seems to fix pretty well with an LCC though. Example below at max shift on the STC which is 18mm.

Dave

 
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G

gazwas

Active member
Jan Brittenson said:
It looks like the camera is aimed slightly up.
Click to expand...
That's a possibility but I checked, then re-checked with a level on multiple surfaces for the test above. Also when rotating the lens 90 degrees it removed the issue. Although looking at how small a movement of the focus rail in needed to adjust focus, a degree or two off level might be contributing. Done some further tests and getting better results but I really need a higher powered loupe to critically focus on the GG..... 8x or 10x I'm thinking.

dchew said:
Gareth,
I've also been playing with my new 43xl (on an Alpa STC). I agree there is definitely a critical sweet spot. I see it every time I go through the shimming exercise on the Alpa w/ HPF rings. I can tell the difference between 12.9 and 13.7 feet. And that's on a 43mm. You should see how sensitive the 100HR is! I'm getting a Leica Disto...

By the way, have you shifted much? Nasty color cast on mine w/ a P65+. Seems to fix pretty well with an LCC though.

Dave
Click to expand...
Hi Dave, I don't have the luxury of using a Disto on an M-Line but I'm working hard on my focusing technique. I have done some shift tests and noted the colour shifts but I was expecting this so didn't really shock me. What did surprise me however was the amount of fall off on the P65+ with the 43XL with zero movements. Thought it would be better for some reason and no problem to correct in C1. When you take the GG off and see how close the rear element of the lens is its not surprising and a pretty amazing achievement by Schenider IMO.

One thing about the 43XL and P65+ is when you nail the focus its astonishingly sharp. Never seen a wide lens as sharp before! :bugeyes:
 
dchew

dchew

Well-known member
gazwas said:
One thing about the 43XL and P65+ is when you nail the focus its astonishingly sharp. Never seen a wide lens as sharp before! :bugeyes:
Click to expand...
Completely agree. I expected to sacrifice some sharpness for image circle, but I don't know how it could be much sharper. Seems just as sharp as my 100HR-S, but there may be some uncontrollable perception in that evaluation!

Dave
 
A

archivue

Active member
By the way,what made you guys choose 43XL over 47XL ?
the 43 is sharper in the angles, and is getting sharp one stop before the 47.

i'm using a 35XL... i've start with a beautiful F line 69, and is was really difficult to deal with field curvature... when i've bought the RM3D, this problem disappear... from then, i can focus on framing... focusing on a ground glass can be a nightmare sometimes !
 
G

gazwas

Active member
archivue said:
i'm using a 35XL... i've start with a beautiful F line 69, and is was really difficult to deal with field curvature... when i've bought the RM3D, this problem disappear... from then, i can focus on framing... focusing on a ground glass can be a nightmare sometimes !
Click to expand...
Hi Archive, so you think this is what I'm seeing on the M-Line?

Why woukd the RM3D not show this as I thought feild curvature is a lens issue not are camera one?

I'm going to pruchase a stronger loupe and do some more testing next week as with a 4x you just can't be sure you've nailed the focus.
 
GrahamWelland

GrahamWelland

Subscriber & Workshop Member
Field curvature is a characteristic of the lens - period. Not sure how the RM3D is supposed to change that :confused:
 
A

archivue

Active member
the RM3D doesn't change it, but using the focusing ring you have it calibrated for the good balance... between center and corner... that's it !

i've test a lot of loupe, and find out that for me (i wear glasses with a small correction)... the more convenient one, was the big rodenstock !
 
GrahamWelland

GrahamWelland

Subscriber & Workshop Member
archivue said:
the RM3D doesn't change it, but using the focusing ring you have it calibrated for the good balance... between center and corner... that's it !
Click to expand...
Aha. Well, yes that makes sense. Nice compromise solution actually to be able to auto dial in your mid-point correction for the lens/sensor pair to accomodate, albeit I guess giving up ultimate sharpness in the centre. :thumbup:
 
S

smei_ch

Guest
gazwas said:
That's a possibility but I checked, then re-checked with a level on multiple surfaces for the test above. Also when rotating the lens 90 degrees it removed the issue. Although looking at how small a movement of the focus rail in needed to adjust focus, a degree or two off level might be contributing. ..........
Click to expand...
When rotating the lens changes the focus, then there must be some manufacturing problems/misalignments. :confused:
 
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