The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Inputs on my newly acquired 35mm lux re: focus shift

blimey

New member
Testing a newly acquired Summilux ASPH after selling all my other lens. Not as good as the deal right now on the for sale forum. I don't even know if I am doing this right so forgive me. This is paired with the M8.

f1.4

f1.4

f1.4

f2.0

f2.8

f4.0

f5.6

f8.0
 
Last edited:

Hosermage

Active member
You know, when I tested my ZM50 C-Sonnar for focus shift, I spread out a piece of paper with lots of text (like newspaper). Then I focused a marker at the MFD at the widest aperture. Once set, I simply take shots as I turn the aperture ring. Reading the lines of text that was focused, I could tell there was about an inch of back-focus at f/1.5 and determined my lens was optimized for f/2.8.

In your case though, even if there was focus shift, I don't think it's as bad as the ZM Sonnar.
 

Double Negative

Not Available
You might also want to focus bracket your wide open shot over say, three or four frames. Just to make sure it's not just a slight misfocus on your part.

Pay attention especially if you just stop down from there - because if wide open is off, all the rest will be also (just hidden by DoF for the most part).
 

blimey

New member
see above. ok i saw a few post about using battery(focus on the word PHILIPS) so i tried it. i can't find a ruler right now. shot at 0.7m(mfd). something is off at f1.4.
 

glenerrolrd

Workshop Member
The batteries need to be placed at different distances . The you focus on the middle battery . This allows you to see where the actual focus point is and how it changes . A good reference is to look at the battery just in front and just behind the target ...do they both look about the same when you focus. This helps minimize focus error.

The 35 1.4 asph has a well known focus shift as you stop down. If the lens is set to be perfect at 1.4 you will have sufficient back focus at f2.8/f4 to exceed your DOF . At f5.6 the DOF catches up but the bias is still back . The optimum focus calibration is to make f2 perfect and allow f1.4 a small front focus ..this is just enough to bring f2.8/f4/f5.6 inside the DOF . You can easily learn to adapt to a minor FF at 1.4 and you probably miss by this much if shooting hand held anyway .

This is a characteristic of the 35 1.4 asph that was corrected by the floating elements in the current version (FLE). Many photographers have worked around this issue and once the camera /lens are calibrated you can make the small adjustments to be consistent .

When testing you should take 3-6 shots to eliminate your own focus errors .
 

SYGTAFOTO

New member
Agree with above. Lens is good as long as you know how to compensate for the deficiencies in the optical design.
Personally, I didn't like the focus shift. I had to intentionally force the rangefinder patch go past the point of overlap, and it threw me off when I switched lenses.
 

fotoism

Member
A couple of easy to find objects to do focus testing:
1. tape a piece of newspaper of the wall and shoot at it at 45 degrees. The classified page is best for this purpose. Mark the point you are trying to focus, shoot several shots as others have suggested to eliminate focusing error on your part, refocus every time. Use a sturdy tripod, and shutter release cable if available.
2. Lay a measuring tape on the floor and do the same, 45 degree angle, several shots, refocus, tripod and shutter release cable.
Oh yes, aperture wide open.
 
V

Vivek

Guest
I do not think (based on the ball/battery photos) there is anything wrong with your lens. You need better light.
 

250swb

Member
The lens is a touch softer at f1.4 anyway, so it is a matter of guessing how much that is involved or if it is focus shift. But from your battery test I don't think you will have so much focus shift in real life photography to make much difference, unless you specialise in photographing batteries.....:D

There is no big jump in focus in your pictures, that is when focus shift can be a big pain when shooting close to medium distance, so if it is off a tiny fraction from where you focused it won't be noticable or be covered by DOF most of the time. I had an otherwise lovely CV 28mm Ultron that was like a bucking bronco with its focus shift at all the sweet to use mid-apertures, so it had to go.

Steve
 
Top