Acceptable Level of Focus Shift on new 35 Lux FLE

[jplomley]

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Looking for some feedback from owners of this lens. I just purchased this 35 Lux FLE new and after evaluating the performance on my M10 and SL have noted there is a shift at f/2.8 and f/4.0 behind the intended plane of focus. At f/1.4 and f/2.0 it is spot-on and continues to be so again at f/5.6. But the f/2.8 and 4.0 performance is somewhat surprising as I was under the impression that by incorporating the FLE that such focus plane shifting had been eliminated. 

 

I'm keen to hear from others with this optic if they have noted similar performance, or if I just happened to get a copy that is out of spec????

 

Cheers for any and all feedback!

Edited January 23, 2018 by jplomley

[Gregm61]

I bought mine just recently, but "only" for take pictures vs. testing for focus shift and in the limited amount of time I've used it for just that and trying a few test subjects at various distances and larger apertures to see how well subjects can be isolated from the background, I've been very pleased having used it at every aperture except f16, but I'll play along here...

 

at f2.8 and f4 are you saying there's focus shift at any and all distances, just up close, or within 10-15 feet? I'm guessing at any distance beyond that, depth of field will render it a fairly moot point.

 

This was an image captured at f4 and a somewhat closer distance and it looks plenty sharp to me.

 

 

f2.8 and focused on the stone at a relatively close distance, looks good enough for me..

 

 

 

I've seen reviews that say yes, there is still some focus shift and I've read Ming Thein's review where he says in all the images he took with it he saw no evidence of focus shift..

 

https://blog.mingthein.com/2013/02/28/leica-351-4-summilux-m-asph-fle-review/

 

I think I'll just keep taking pictures as it seems to work well just used for that, and let all the measurebaters debate this.

Edited January 23, 2018 by Gregm61

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[lct]

Never seen any focus shift with mine but i'm no pixel peeper. Now focus shift is like headache, if you look hard for it it will be there .

[Jared]

I have not experienced any focus shift with my 35mm FLE.  If I focus at f/1.4, the point of optimum focus is either identical at all smaller apertures or, at a minimum, well within the depth of field for any reasonable circle of confusion size.  What I have noticed with the 35mm FLE is that the field curvature is a little odd--it doesn't seem to be a simple sphere.  If your testing happened to involve any subjects that were off center, that might add a layer of complexity you weren't expecting.  

 

On axis, though, I have never noticed a different point of best focus at f/2.8 or f/4 vs. wider apertures.  If you do have focus shift, it is likely present at all apertures, but the larger DOF at f/5.6 and beyond is able hide the shift.  If you just bought the 35mm FLE from a reputable dealer, I'd recommend exchanging it for another sample.  Your experiences do not match mine or the general consensus. on this lens.

[Jared]

I have found this article to be the most comprehensive I have seen on the performance (at least in terms of image quality) of the 35mm FLE.  

 

http://tashley1.zenfolio.com/blog/2013/4/leica-m-240-with-35mm-f1-4-fle---some-observations

 

Tim did find there was a small amount of focus shift in his sample, but never enough to allow the point of focus to move outside the DOF for his camera.  However, it was enough that the zone of critical focus would start out primarily in front of the focus point and shift to being primarily behind the focus point, then widen enough that it wasn't particularly relevant.  I've never done the kinds of measurements Tim performed, so couldn't tell if my sample performs the same.  I just know that if I focus wide open at f/1.4 in the center of the frame at a distance of 1.5m or so, and then stop down to f/2, f/2.8, f/4, etc. there is no point at which apparent sharpness decreases until diffraction sets in.  So if there is any focus shift on my sample, it is not enough for the focus point to move outside the "critical focus" range, and it is more than offset by the improved resolution and contrast as the lens is stopped down.  By f/4 or so, my FLE achieves its highest performance and maintains that level until f/8 or so (on full frame).  

[hoppyman]

Jeff you can see a focus shift from spot on at f/2 to f/2.8? Presumably you are doing some kind of bench testing? Mine ( early production) actually proved to have a very significant adjustment error at minimum distance and large apertures. It was adjusted perfectly by this countries agent for mel

As far as I know some focus shift is inherent with every lens, while it may not be significant.

I recall that LFI published a comparison on shift with the new vs old Summilux . They confirmed a reduction in this effect amongst other performance changes

[lct]

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I wonder if some reviewers are not mistaking focus shift for front or back focusing and/or field curvature here. Could someone explain the difference more accurately than i could do?

[Exodies]

I always thought focus shift occurred when you changed aperture but it’s not a phenomenon I have experienced.

[epand56]

Many say that the Lux 35/1.4 Asph. non Fle has even more shift. I have mine since years and is the only lens I will never sell or change with another 35.

It is on my camera 80% of the time. 

[M11 for me]

I always thought focus shift occurred when you changed aperture but it’s not a phenomenon I have experienced.

I wonder too. Is it that you focus perfectly well through the rangefinder and then, depending on the aperture, the point that you focused on is sharp or not. Is that it? And how would you then be able to correct that without using LV?

[otto.f]

There was another thread about this topic earlier in which misunderstandings were revealed about the concept of focus shift. Since OP mentions the SL with which camera he diagnosed focus shift I suspect that there is again a misconception of what focus shift actually is. On an SL you cannot suffer from focus shift because you look through lens and will correct it without even knowing it occurs. When a lens has focus shift you can only go wrong with a rangefinder, not with a (D)SLR, a mirrorless system or any other camera which looks through the lens.

Focus shift in general is quite normal for lenses and I bet that many R lenses have it, also TC lenses and enlarger lenses for analogue printing.

 

But, to answer the question: no, I did not experience any focus shift with the 35 FLE in 4 years and I tested it in the beginning precisely because this lens was introduced with the assurance that focus shift was corrected.

Edited January 24, 2018 by otto.f

[elmars]

With modern lenses focus shift is not a practical problem, even with a rangefinder.

[elmars]

They are constructed to minimise focus shift, especially the aspherical lenses.

[Exodies]

Nobody is saying what it is.

[otto.f]

Nobody is saying what it is.

The focus shifts when changing the aperture, so not every aperture has the same focus plane.

[pgk]

From Leica's datasheet: "In comparison with its predecessor, the new LEICA SUMMILUX-M 35 mm f/1.4 ASPH. now incorporates a floating

element: the lenses behind the aperture blades are constructed as a floating group that changes its position relative to the front

lens group during focusing to ensure that the LEICA SUMMILUX-M 1:1.4/35 mm ASPH. achieves equally outstanding imaging performance

at closer focusing distances." So the FLE (floating group) is designed to improve close range performance and not to deal with any focus shift.

 

Aperture dependent focus shift is a shift in the point of focus as a lens is stopped down so is aperture dependent. I have the pre-FLE version of the Summilux and aperture dependent focus shift isn't a problem in practice. If it is significant, then it may be that the lens needs adjustment because the optics are not in the precise positions that they should be.

[pico]

To insert a disruption - if film accommodates minor focus shift, why cannot digital modulate to achieve the same? Is the firmware  not smart enough? Is it time to consider engineering focus to the sensor in a more intelligent way?

[Exodies]

All it needs is a way of moving the sensor and a way of telling it what to focus on.

[hoppyman]

I want that sensor nailed down and the lenses perfectly adjusted, AF calibrated perfectly for that, the whole system set up as precisely as possible. For sure there is a market position for multi focus cleverness. Not on my Leica stuff thanks!

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Hallo,

Look here: Leica M

[epand56]

I must say that the reason why I like using a Leica M is because of its randomness, because the pictures it takes are never too much perfect, because, being manual, you never know the exact result and because sometime an error create a wonderful picture.

In short I love it because it's like me.

Edited January 25, 2018 by epand56