Do I have a problem with my 35mm Asph? (Naked focus chart)

[jfgilbert]

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Hello,

I finally got back both my upgraded M8 body and my coded lenses within a couple weeks of each other and started playing again. I had the impression that my 3 months old 35/1.4 was kind of "soft" so I suspected a focus problem and checked it with the focus chart.

Camera is on a tripod at about 7' from the chart. 1/90s, f1.4, ISO 160, delayed shutter. I am attaching the full picture from the 35mm, a 100% crop of the chart and, for comparison, a 100% of the same pic made with my 25 year old 50/f2. It seems to me that the 35mm does not have a focus problem but is just not sharp.

Could the collective wisdom of the forum let me know if I am expecting too much or if something is wrong with that lens?

Thank you,

Jacques

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[ho_co]

Jacques—

1) Your test looks reasonable and careful.

 

2) As you are aware, the current 35/1.4 is considered one of the best lenses Leica has ever made.

 

3) Like all Leica lenses, it is amazingly good wide open. But wide open it is still not at its best.

 

4) Most tests I’ve seen using this chart have been from a much closer distance (not that that is better or worse, just that we’re not used to seeing a test like this one). In other words, this is a greater enlargement than we usually see. I think that’s why the test chart seems simply fuzzy, with no particular area noticeably sharper.

 

5) I would therefore try the same test at f/2 or f/2.8 before drawing any conclusion about the lens.

 

6) My feeling is that you are simply seeing the fact that this lens is not at its best wide open. The contrast will likely pick up dramatically and the image will not look ‘fuzzy’ if you stop down just one or two stops.

 

7) You are probably aware that this particular lens has been the subject of a couple long threads on the forum. But the problems shown there were of a completely different sort and tested differently.

 

8) Lens design for wide angles faces a different set of problems from lens design for a normal lens. Comparing a 50 with a 35 isn’t really profitable in a situation like this because the two lenses see a much different angle. That is why the image from the 50 looks so much bigger: It hasn’t been magnified as much to make the full-chart crop. The way to make a reasonable comparison of the two focal lengths would be to adjust the camera-to-target distance so that the image is rendered the same size with both lenses. (I know, you wanted to check focusing accuracy; you’ve seen that the 50 Summicron is perfect at this distance, and you’re still not sure what to make of the results of the 35 Summilux: That is, the question has changed.)

 

9) Comparing an f/2 with an f/1.4 isn’t fair either, even if both are of the same focal length, because doubling an aperture increases the aberrations by four times.

 

10) So again, check the 35 stopped down to f/2 or f/2.8. That will indicate whether you have a problem with the lens.

 

Strictly my opinion; to be tempered with the insights and experiences of others here.

 

--HC

[bsmith]

Even at 1.4, mine is razor sharp.

[Guest guy_mancuso]

Here is a quick test that i do all the time with a lens. go outside until you see the four corners of a intersection of the sidewalk and at a angle approximately 45 degrees shoot the very middle of the intersection , than even on the LCD zoom in and see if it backfocused or front focused if not than your dead on. i do this in the field sometimes. Here is one checking the 90macro at F4

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[jfgilbert]

Guy, thank you for the elaborate response. I understand that the extra stop has an effect on distortions but I find it a little disappointing that I would have to close it a stop or two to get the crisp detail the camera is capable of. I thought the aspherical element (and the extra $2k) were there to take care of it.

As you mention, it does not look like the front/back focus problem that has been discussed before because it is not really sharp anywhere. If this is normal and that's the best that it can do, I am not sure I want to keep it.

Cheers,

Jacques

[tashley]

Jacques, it's not normal! I'm one of the guys that has tested a few of these on a few bodies and wide open, it should be sharper. Respectfully to HC, when you repeat the test, DO use the lens wide open to start with: it should be very sharp even at that aperture and testing it there will eliminate any effect caused by focus shift issues as you stop down. Don't shoot the chart at an angle for the first test: just tape it very flat to a wall and shoot it dead on from about 1 metre away, focussing very carefully. Take one shot at F1.4 and one at F16. The F1.4 shot will tell you if it is basically sharp or not, the F16 will compensate for any but the worst misfocus and RF misadjustment. At least one of these two shots should be pretty damn sharp.

 

Now you can shoot the chart on the table again from a 45 degree angle and at every F stop, to see what behaviour the lens has with changes in aperture. Get the plane of the sensor about 1 metre from the centre of the chart again.

 

It is really vital, vital, vital that you use a tripod throughout: at wider apertures, even a small shift in body position affects focus and at tight apertures, the shutter speed will be slow and you need to be 100% certain that any effects you see are due to focus not shake.

 

Hope that helps

 

Tim

[frc]

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Shutterspeeds shouldn't be to slow shooting wide open, Tim;-)

 

Jaques,

 

There are many different types of photographers and each of them have their own wishes and expectations of a lens.

The Lux 35 asph has never had a reputation of being an extremely sharp lens, this is simply not one of its virtues.

The cron 35 asph is more highly accredited in this field.

On other specs though the Lux is a great performer, colour rendition, flare resistance, the out of focus feild and its unique painterly imaging.

I use this lens as an allround rep. and doc. lens it being a mild wide angle on my traditional M, on the M8 it becomes a standard angle lens giving you the possibility of using it for portraits at close distance.

And remember, a fast lens is more expensive because it allows you to take a picture uder lightconditions where no one beleives you can manage without a flash, not because it is the sharper lens!

Try your lens in the real world ( I never came across test charts doing street photography ) and see how it behaves.

I know I am a bit biassed regarded to this lens, the advocate of the 35 1.4 devil, but don't reject a lens without trying it in different situations.

 

The attached uncorrected ( no sharpening or colour enhancement ) pic is backlit lowlight Provia 400 1/15 f1.4 with motion blur, I'm not a tripod.

 

Regards Francis

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[lct]

Motion blur is not the best way to show the sharpness of a lens obviously but i'm a bit surprised by the softness of those pics personally.

I don't own the 35/1.4 yet but i would have expected that it is not that far from the 50/1.4 asph.

Any other pics at f/1.4?

[wattsy]

The Lux 35 asph has never had a reputation of being an extremely sharp lens, this is simply not one of its virtues.

The cron 35 asph is more highly accredited in this field.

 

I'm not sure I can agree with this, Francis. I have both lenses and the 'lux is an extremely sharp lens - in my opinion more so at F1.4 than the 'cron is at F2. The 'cron is often described as an F2 version of the 'lux but I think they are quite different in the way that they 'draw'. As odd as it may sound, the 'cron appears to have a more expansive depth of field than the 'lux at equivalent f stops. The plane of focus of the 'lux seems to fall off from sharp to unsharp more quickly when compared with the 'cron. The 'lux definitely has the more 'interesting' look (not just wide-open) but it undoubtedly does have issues with focus-shift.

[Jamie Roberts]

My 35 f1.4--like Tim's (we agree!!) seems much sharper wide open than the post.

 

But--it is true f2.0 is not f1.4. Having said that, most M summiluxes are fantastic wide open.

 

But leaving aside processing differences, your 50mm has more effective resolution on the target (being longer, it has more pixels describing the same thing), and since you evidently didn't compensate for that effect (by moving the tripod back), the comparison is somewhat useless, IMO...

 

(oh, I also find that given enough light and a fast enough shutter, there's no need for a tripod, though it's still a good idea for testing)

[californiajay]

Somehow I feel that the relative low contrast of this scene is contributing to its apparent lack of sharpness. Do the same test with a flash or outside on a bright sunny day and compare. I think you will be happier with the results.

[bsmith]

The Leica 35mm f1.4 even at 1.4 is one of the sharpest lenses Leica makes. Don't let anyone tell you it's not tact sharp at 1.4

[4X5B&W]

"As odd as it may sound, the 'cron appears to have a more expansive depth of field than the 'lux at equivalent f stops. The plane of focus of the 'lux seems to fall off from sharp to unsharp more quickly when compared with the 'cron."

 

Glad to hear someone else sees this as well, I have always attributed the greater perceived depth of field as a function of better "flatness of field" of the lens design.

 

Regardless the 35 ASPH Cron's depth of field for any given F stop, has always impressed me. A superb lens.

[bsmith]

The 35 lux is so good that if I could only have 1 lens it would be that lens, ... no question or hesitation. (on a M8 or M film body)

[jfgilbert]

Thank you all for the helpful tips, opinions, and responses. I suspected that it was not quite as good as it could, that's why I made the test. I don't usually shoot focus charts or from a tripod, but I wanted to eliminate as many other causes of blur as possible.

I will make a few more tests when I am back home, but I am getting the feeling that something is not quite right. I attach a recent portrait that arose my suspicions. It is ISO 640, so there is a little more noise (no NR), but I feel that the 100% view should be sharper.

Thank you,

Jacques

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[Guest guy_mancuso]

Looks like it backfocused slightly. Look at here hair in the first shot , that is the focus point on the right

[tashley]

 

(oh, I also find that given enough light and a fast enough shutter, there's no need for a tripod, though it's still a good idea for testing)

 

 

BAD boy Jamie! It is literally impossible to do this test accurately without a tripod: you have to ex-out everything but the F-stop and have all other factors common. Really. Otherwise you might have slightly better focus in one shot than another and regard it as a function of the lens when it is really a function of you....

 

 

Hope you're well!

 

Tim

[jcbjr]

jacques- my opinion, though this comes from a terribly unscientific comparison of your images posted here and my own experience with the same 35 lux lens, is that my images are sharper than what you have shown here, perhaps by a good margin. i agree with some of the suggestions to try to control your testing a bit more, but the best thing to do would be to get another 35 lux, perhaps as a loaner from your local dealer (or buy one to be returned if not satisfied with it), and simply compare the images each makes under controlled conditions. unless you have two dog lenses, you'll find the answer. good luck.

 

john

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[ho_co]

Just to follow up--

Tim suggests f/1.4 and f/16. Don't stop down beyond f/8 because that brings diffraction into play. (By the way, he is the person who has done most testing on this particular lens; his opinions count.)

 

If you simply look at the picture you posted--not at the chart, but at the overall picture--the image is quite crisp. Look at the carpet, the edges of the table, the (what is that?) bomb-making material (?) at the left. They're all good. The problem with the chart is that at this magnification you are dealing with micro-contrast to try to make it legible.

 

In addition, the image lighting is low-contrast. Lighting is from the far end of the room and therefore illuminates the focus chart in a glancing way, which further reduces contrast.

 

That's why I say your first bet is to stop the lens down one or two stops, just to compensate for the negatives you've thrown at it. You're trying to test too many things here. To test a lens's performance, you need good lighting (unless you're doing flare tests, of course).

 

All the other tests people suggest are fine, but you started with one test. I say first adjust the lens and continue with that same test--at which point I think you'll find the lens is fine--and then go do the other tests.

 

--HC

[frc]

The technical specs I mentioned in my post were there to prevent a discussion about only the absolute sharpness of this lens.

What I wanted to show was its ability to capture images without flash that would otherwise not have been possible.

Focussing for this pic was done in less than half a second, this is almost a guaranty for error.

The long exposure doesn't do any good for sharpness either, but there is no other option except for an even higher iso. ( more loss of detail due to larger grain )

Given the strong backlight and the lack of direct light on the subject, hardly anybody is as crazy as to try such a shot and definitely not in a split second.

The picture I posted was intended to show the lenses ability to record a scene like this without any flare or ghosting.

For sharper or test chart pictures I suggest a low iso shooter using a tripod posts examples.

I've got sharper pics but handhelt at 400 iso doesn't reveal much in terms of the absolute sharpness.

 

Anyone having more critisism about my use of this 35 mm light marvel, flame me,I get over it;-)