Leica 35mm f1.4 FLE falut?

[CheshireCat]

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Hi , I have the 35mm FLE LUX lens that I believe you are referring to, and I am confused with your above references to "hyper focus". What is this ?

 

The OP actually meant "hyperfocal distance".

[Halliday]

Dear dugby, I would be most interested if you could check your lens to see if the same thing happens. The procedure is a way of trying to maximise DOF. I was reporting the above effects from aligning the centre of the infinity mark with the f5.6 mark on the right side of the lens barrel. The theory is that you gain more foreground sharpness while maintaining sharpness to infinity. On my lens the consequence is an image with a sharp enough foreground and centre of image (including middle and distant objects), but middle and distant objects to the sides of the image are weak/blurred when only slightly enlarged. Does your lens do this, what Wattsy would call, 'eccentric' thing?

Best, Halliday

[k-hawinkler]

Hi Halliday,

 

I don't own that specific lens. I own the previous version.

Based on your descriptions and Tim Ashley's experiences I would like to suggest to send your lens to Leica and have them assess and repair it. I can't believe that your lens works as intended. FLE lenses are pretty tricky and it's best to ask Leica to work on them.

 

I bought brand new the 50 mm Summilux-M ASPH that, as far as I know, also is an FLE design. I had to send mine in as it didn't focus correctly.

 

Good luck with your lens!

[CheshireCat]

Halliday,

I own an excellent copy of the 35 FLE (arguably the best 35mm lens for full frame).

Just fired a few test shots and the results are consistent with your examples.

As expected.

 

Your Summicron being sharp in the "same" conditions is probably due to the fact that the lens design is quite different, and/or the markings on the barrel are not precise enough to ensure you are really focusing the lenses at the same actual focusing distance.

If you want to compare the lenses, just put a dummy subject at hyperfocal distance, and focus with Live View. You will just be comparing lens design though.

 

There are different online calculators for hyperfocal distance that correctly take into account the pixel pitch. Try them, and compare the distance with the ridiculous 15 feet suggested by the lens markings.

Then you will understand why I am proposing to replace lens markings with a latin motto.

[dugby]

Dear dugby, I would be most interested if you could check your lens to see if the same thing happens. The procedure is a way of trying to maximise DOF. I was reporting the above effects from aligning the centre of the infinity mark with the f5.6 mark on the right side of the lens barrel. The theory is that you gain more foreground sharpness while maintaining sharpness to infinity. On my lens the consequence is an image with a sharp enough foreground and centre of image (including middle and distant objects), but middle and distant objects to the sides of the image are weak/blurred when only slightly enlarged. Does your lens do this, what Wattsy would call, 'eccentric' thing?

Best, Halliday

 

Hello Halliday. Thankyou for your explanation, which is clear.

 

My understanding (based upon 40 years ago - learning) is that the DOF scale was a primitive method of showing what "could be" in focus against the distance scale on the lens.

 

This "hyperfocal" concept is new to me.

 

However I would have expected the results that you and others have reported, when setting the "infinity" mark to "DOF f5.6 mark" ( presumably chosing the one closer to infinity and NOT the one closest to minimum distance), This is substantiated when I look at the 35FLE's DOF charts in the manual.

 

I have noticed the "wave DOF" that Tim Ashley has reported, as it's caught me off focus a couple of times mainly in low light where I cannot range-find the subject that well, so I hunt for a focus point in a similar plane to my subject, but upon re aligning the subject, and shoot - I get a blurred subject.

[adan]

I find it hard to believe that a lens can be soft in the center at f/4 and not at f/1.4.

 

Not that hard to do.

 

Lens designs are always compromises that pick and choose between various faults and strengths.

 

If I were a designer charged with designing an f/1.4 lens, my own thoughts would be "The only advantage to a fast lens is that it performs well at f/1.4. A lens that performs like an f/2 lens from f/2 to f/16, and is soft at f/1.4, seems pointless. Bigger and more expensive, with no real gain for the money."

 

The non-ASPH Leica 35 f/1.4 from 1961-1995 was like that - same as an f/2 at most apertures, but kinda dreamy and glowy (to be generous) at f/1.4.

 

So I'd spend most of my computer time optimizing for the light rays from the edges of the glass - the ones that are used wide open down to perhaps f/2.8 (and cut off by the aperture blades at smaller apertures) - and are the most difficult to corral.

 

The light rays that will still get through the center of the lens stopped down to f/4 aren't as important to my goal (they will only be delivering 1/8th of the light at f/1.4 - I'd choose to focus (hee-hee) on the other 7/8ths).

 

If forced to choose - and that is the point: lens designers are ALWAYS forced to choose. Unless they have absolutely unlimited size, weight, equipment and material "budgets."

 

So at f/1.4, I get a fairly sharp image, with 1/8th of the light (from the center of the lens) perhaps a bit poorer in focus or other performance factors than the other 7/8ths fom the outer part of the lens.

 

Stopped down to f/4 - now I'm getting only the "poorly directed" light rays.

 

That's an exaggeration of course - the center light rays might only be "not quite as good" rather than "poor." But it demonstrates the principle.

[CheshireCat]

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Andy, thanks for your explanation. It makes sense, but it applies only to the design stage.

 

But given that:

- My 35 FLE outresolves the M sensor at f/4. This means that the lens design is more than good enough for f/4.

- The post was referring to a problem with his/her own copy of the lens, at f/4 only.

 

Now, how can that copy of the lens have a defect that shows at f/4 only, and not at wider or smaller apertures ?

The only reason I can think of is focus shift at near focusing distances, but that should be balanced by the FLE. So either the post was referring to the previous non-FLE version, or the FLE was not working correctly (but in this case, the issue should be noticeable well before f/4).