Home · Register · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Sony Forum | Join Upload & Sell

1       2              4              7       8       end
  

FM Lens test for Centering (Mount tilt / swing)

  
 
marathon
Offline

Upload & Sell: Off
p.3 #1 · p.3 #1 · FM Lens test for Centering (Mount tilt / swing)


Another example of the same sort of what I call 'the 4 corner test'.

http://www.gletscherbruch.de/foto/test/dezentrierung/dezentrierung.html

In German but google translates easily ( if you need it ) The pics tell all.



Feb 11, 2019 at 03:17 AM
s4ducati
Offline
• •
Upload & Sell: On
p.3 #2 · p.3 #2 · FM Lens test for Centering (Mount tilt / swing)


Indeed the same test as FM has described and used here.

An interesting note however that I have note seen referenced to is the idea that the sensor may be mis-aligned too.

I wonder how often the sensor alignment is out of spec in higher end cameras?



Feb 11, 2019 at 08:25 AM
technic
Offline
• • • •
Upload & Sell: Off
p.3 #3 · p.3 #3 · FM Lens test for Centering (Mount tilt / swing)


s4ducati wrote:
Indeed the same test as FM has described and used here.

An interesting note however that I have note seen referenced to is the idea that the sensor may be mis-aligned too.

I wonder how often the sensor alignment is out of spec in higher end cameras?


Yes, sensor misalignment happens (or mount misaligned, depends on how you define things). I remember some stories about a recent Nikon DSLR camera where this was noticed in early production runs - probably due to the higher resolution which makes such things more obvious. But if you have just one lens and body it is difficult to say which one is the culprit, and even if you have several lenses it may not be entirely clear ;(



Feb 11, 2019 at 09:18 AM
naturephoto1
Offline
• • • • • •
Upload & Sell: Off
p.3 #4 · p.3 #4 · FM Lens test for Centering (Mount tilt / swing)


s4ducati wrote:
Indeed the same test as FM has described and used here.

An interesting note however that I have note seen referenced to is the idea that the sensor may be mis-aligned too.

I wonder how often the sensor alignment is out of spec in higher end cameras?


technic wrote:
Yes, sensor misalignment happens (or mount misaligned, depends on how you define things). I remember some stories about a recent Nikon DSLR camera where this was noticed in early production runs - probably due to the higher resolution which makes such things more obvious. But if you have just one lens and body it is difficult to say which one is the culprit, and even if you have several lenses it may not be entirely clear ;(


We suspected that my original A7r sensor was out of alignment when testing a number of lenses including my Zeiss 35mm f1.4 ZM and other lenses at or near wide open (when using 2 adapters) after the camera had a Kolari thin sensor stack modification (apparently the camera was originally out of alignment). All of the lenses tested showed the same corners being out of focus when focusing on the center as well as on the corners. This was confirmed and corrected by Kolari when they changed the V2 sensor cover to a V3 sensor cover. Kolari spent the time and aligned the sensor, calibrated the focus of the camera, and confirmed that both my original Phigment and Hawk's Factory Helicoid V5 Leica M to NEX adapters were fine at no additional charge.

Rich




Feb 11, 2019 at 09:40 AM
Rob L
Offline
• •
Upload & Sell: On
p.3 #5 · p.3 #5 · FM Lens test for Centering (Mount tilt / swing)


I wonder if these newer autofucus lenses with the focus element or group riding on rails have difficulty keeping the focus group aligned? Seems like it would be difficult to avoid some play. I have tested a few lenses and gotten inconsistent results. My Zony 35 1.4 tested great at 1.8 and not so great at f/4 and f/5.6


Feb 11, 2019 at 10:10 AM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.3 #6 · p.3 #6 · FM Lens test for Centering (Mount tilt / swing)


Itís the first thing I test when getting a new body. I usually use a lens that I know is perfectly centered. I have seen bodies with tilted mount/sensor registration.

s4ducati wrote:
Indeed the same test as FM has described and used here.

An interesting note however that I have note seen referenced to is the idea that the sensor may be mis-aligned too.

I wonder how often the sensor alignment is out of spec in higher end cameras?




Feb 11, 2019 at 10:50 AM
David Cartagena
Offline

Upload & Sell: Off
p.3 #7 · p.3 #7 · FM Lens test for Centering (Mount tilt / swing)




AZSteve wrote:
Fred, since this thread has been revived I want to mention that I recently had an experience with your centering test methodology versus Jim Kasson's Siemens-star test, where a lens that appears to pass the latter fails the former. (Your post of 1 Sept.)

B&H had a one-day deep sale on the Sigma Art 85mm and I took the bait. The first four images I took were Siemens stars in each corner, and then I went on to images of nearby mountains, a slight variation on your procedure. The stars looked passably similar and I was much relieved that I'd been
...Show more

Focus distance. The lens elements rotates or at least move when focussed, so it won't necessarily be equal centered at different focus distances.

David




Feb 11, 2019 at 12:48 PM
AZSteve
Offline
• •
Upload & Sell: Off
p.3 #8 · p.3 #8 · FM Lens test for Centering (Mount tilt / swing)


David, Kasson's star test is to be conducted at what we might call "effective infinity", which he has an involved way of characterizing based on f-ratio, focal length, pixel size, etc.


Feb 11, 2019 at 01:47 PM
technic
Offline
• • • •
Upload & Sell: Off
p.3 #9 · p.3 #9 · FM Lens test for Centering (Mount tilt / swing)


naturephoto1 wrote:
We suspected that my original A7r sensor was out of alignment when testing a number of lenses including my Zeiss 35mm f1.4 ZM and other lenses at or near wide open (when using 2 adapters) after the camera had a Kolari thin sensor stack modification (apparently the camera was originally out of alignment). All of the lenses tested showed the same corners being out of focus when focusing on the center as well as on the corners. This was confirmed and corrected by Kolari when they changed the V2 sensor cover to a V3 sensor cover. Kolari spent the time
...Show more

good to hear that Kolari spent the time for correcting that and did a good job

In most camera's this is a lot of work and often it is impossible (at least without dedicated factory equipment) to align the sensor exactly with the camera partly disassembled to access the sensor alignment parts (usually some small screws/clamps/shims etc.). Using trial and error often means more risk of sensor dust etc. ...



Feb 11, 2019 at 03:02 PM
rwwright
Offline
• •
Upload & Sell: Off
p.3 #10 · p.3 #10 · FM Lens test for Centering (Mount tilt / swing)


I guess I am old and not very smart. could someone post 4 photos taken with a decentered lens and tell us how you know that.

anyway I took some photos with my samyang 35 f2.8 and with my batis 135 f2.8 and the same object I focused on look about the same amount of sharpness (use 1/400 sec iso 400 overcast and kinda rainy).
these are the 4 corners from each shot with the 135, raw 7rm3, crop then export jpg full sized

**sorry -- I think these are 32meg files***

OK now just 4 meg files (full size for cropped portion). I did mention my problems above.

https://www.flickr.com/photos/ronaldwright/albums/72157678586519468



Feb 11, 2019 at 04:08 PM
 


Search in Used Dept. 

David Cartagena
Offline

Upload & Sell: Off
p.3 #11 · p.3 #11 · FM Lens test for Centering (Mount tilt / swing)


AZSteve wrote:
David, Kasson's star test is to be conducted at what we might call "effective infinity", which he has an involved way of characterizing based on f-ratio, focal length, pixel size, etc.


Hi Steve.

Ok. but a lens can still be different cantered or decentered depending on the focus distance ;-)
If the lens elements rotate during focusing the unsharp area will change place too.

David



Feb 14, 2019 at 11:02 AM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.3 #12 · p.3 #12 · FM Lens test for Centering (Mount tilt / swing)


David Cartagena wrote:
Hi Steve.

Ok. but a lens can still be different cantered or decentered depending on the focus distance ;-)
If the lens elements rotate during focusing the unsharp area will change place too.

David


That's definitely true but from my experience testing "prime" lenses, if it's well-centered at infinity, it's also great at other distances too.



Feb 14, 2019 at 12:12 PM
David Cartagena
Offline

Upload & Sell: Off
p.3 #13 · p.3 #13 · FM Lens test for Centering (Mount tilt / swing)


Fred Miranda wrote:
That's definitely true but from my experience testing "prime" lenses, if it's well-centered at infinity, it's also great at other distances too.


OK. I Understand. My Sony 55 f/.8 are sharper in the corners at short distances than at infinity. So it's definitely not getting worse at shorter distances;-)



Feb 14, 2019 at 05:05 PM
CWPhotography
Offline

Upload & Sell: Off
p.3 #14 · p.3 #14 · FM Lens test for Centering (Mount tilt / swing)


I have always used this test to check new lenses and it has never let me down, I will also try Fred's test with future lenses.








Feb 14, 2019 at 05:12 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.3 #15 · p.3 #15 · FM Lens test for Centering (Mount tilt / swing)


CWPhotography wrote:
I have always used this test to check new lenses and it has never let me down, I will also try Fred's test with future lenses.

https://cvp.com/images/products/altimage/08-12-20151449587051test-chart.jpg


Prepare yourself to be disappointed as unfortunately it's uncommon for a lens to be equal at all four corners, especially when testing it on a high MP sensor. My copy of the Loxia 21/2.8 used as sample here is one of them...but I went throught 3 copies.
IMO, testing at infinity is easier and preferred as the alignment variable is removed. Trustworthy MTF charts like LensRentals and Zeiss are tested at infinity distance.

Of course there are lenses with low variance but I think it's more related to optical design complexity than tolerance although the latter plays a role. That's even for primes and from any brand. I'd say it's pretty unlikely a zoom lens is perfectly centered at all focal lengths.



Feb 14, 2019 at 05:35 PM
RCicala
Offline
• • • •
Upload & Sell: Off
p.3 #16 · p.3 #16 · FM Lens test for Centering (Mount tilt / swing)


Fred Miranda wrote:
I'd say it's pretty unlikely a zoom lens is perfectly centered at all focal lengths.


I've only tested 5,000 zooms so far so all I can say is the frequency of a zoom perfect at all focal lengths is lower than 1 in 5,000.



Feb 17, 2019 at 03:35 PM
mogul
Online
• • • •
Upload & Sell: On
p.3 #17 · p.3 #17 · FM Lens test for Centering (Mount tilt / swing)


Fred Miranda wrote:
Prepare yourself to be disappointed as unfortunately it's uncommon for a lens to be equal at all four corners, especially when testing it on a high MP sensor. My copy of the Loxia 21/2.8 used as sample here is one of them...but I went throught 3 copies.
IMO, testing at infinity is easier and preferred as the alignment variable is removed. Trustworthy MTF charts like LensRentals and Zeiss are tested at infinity distance.

Of course there are lenses with low variance but I think it's more related to optical design complexity than tolerance although the latter plays a role. That's even
...Show more

Lucky (if want to call it that) my 99II allows all 4 corner micro adjust...it would have to be really bad for me to go in and adjust a zoom wide then tele and then the 4 corners at each distance.



Feb 17, 2019 at 03:43 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.3 #18 · p.3 #18 · FM Lens test for Centering (Mount tilt / swing)


RCicala wrote:
I've only tested 5,000 zooms so far so all I can say is the frequency of a zoom perfect at all focal lengths is lower than 1 in 5,000.


Hi Roger,
What's the variance frequency for primes?



Feb 17, 2019 at 04:47 PM
RCicala
Offline
• • • •
Upload & Sell: Off
p.3 #19 · p.3 #19 · FM Lens test for Centering (Mount tilt / swing)


Fred Miranda wrote:
Hi Roger,
What's the variance frequency for primes?


It depends greatly on which prime and how sensitive we look. Our standard is <10% variation at 30 lp/mm is perfect (I really careful pixel peeper with a high resolution camera might be able to see that, just barely, in some shots. But they would have to work hard to do it.)

At that standard there are a few primes where none are perfect. A really good prime would be over 90% perfect rate though, and most get to 95%.

There are good zooms where 95% are perfect at one focal length but never seen one perfect at all 3 we test (both extremes and the mid point). There's just too many things moving.



Feb 18, 2019 at 11:53 AM
RCicala
Offline
• • • •
Upload & Sell: Off
p.3 #20 · p.3 #20 · FM Lens test for Centering (Mount tilt / swing)


Fred Miranda wrote:
Hi Roger,
What's the variance frequency for primes?


It depends greatly on which prime and how sensitive we look. Our standard is <10% variation at 30 lp/mm is perfect (I really careful pixel peeper with a high resolution camera might be able to see that, just barely, in some shots. But they would have to work hard to do it.)

At that standard there are a few primes where none are perfect. A really good prime would be over 90% perfect rate though, and most get to 95%.

There are good zooms where 95% are perfect at one focal length but never seen one perfect at all 3 we test (both extremes and the mid point). There's just too many things moving.



Feb 18, 2019 at 11:53 AM
1       2              4              7       8       end






FM Forums | Sony Forum | Join Upload & Sell

1       2              4              7       8       end
    
 

You are not logged in. Login or Register

Username       Or Reset password



This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.