Very interesting answer from Leica on 35mm 1.4

[sean_reid]

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Hi Tim,

 

I'll need to check that. But there's a confounding issue here as well. Earlier I quoted from my own draft saying:

 

"This kind of focus bracketing is necessary for any resolution comparison because A) We're human and our eyesight is not perfect and Even the best rangefinder mechanism is a mechanical device with a finite amount of precision. There is also a tiny amount of play within the various mechanical pieces that link the lens to the rangefinder, etc. The M8 uses what is probably the highest quality rangefinder ever integrated into a small-format camera but one can still move a focus ring a tiny amount without disturbing the alignment of the rangefinder windows. The M8 is vastly better than the Epson R-D1 in this respect but it can't be perfect and so focus bracketing is needed for precise evaluation."

 

So, sometime a slight tweak of the focus ring in either direction is correcting for human error or mechanical tolerances, not necessarily for any misfocusing in the lens, per se.

 

More later.

 

Cheers,

 

Sean

[tashley]

Tim and others with the backfocus problem,

 

Did you follow this thread where people have adjusted their M8's rangefinders?

http://www.leica-camera-user.com/digital-forum/13933-new-backfocus-thread-solution.html

 

Have you checked enough (fast) lenses to be able to remove the camera from the equation? I am not 100% sure I trust my M8's rangefinder (thanks also to Michael for his comment pointing this way).

 

 

Thanks for pointing it out - I already exed my RF calibration out of the equation, since I have two bodies ( I tweaked the RF on one of them) and they both work well on most lenses. It's not even short lenses in general that give me problems, just the 35's and one 28. My WATE and my 24 f2.8 were both fine, my 50 lux is fine, 90 macro fine and Jono's 28-35-50 was good too!

 

Tim

[xrogers]

To provide another data point (and data for a recently coded older Lux ASPH), I just ran through a test of my two 35s (yeah, I'll get around to selling one someday...). Shots on tripod at 1 meter and at 10 meters, all full aperture stops (1.4, 2.0, 2.8, etc., through 16), ISO 160 DNGs.

 

The 35 Lux ASPH was coded at New Jersey in February, and the Cron ASPH is uncoded. Lux serial number 38895xx, Cron 38474xx.

 

With the Lux at 1 meter, I do see that slight backward focus shift at 2.8, and a more visible shift at 4.0. Diffraction shows an overall softening at f16. The focus point is always in the range of maximum sharpness. A top notch performance.

 

My shots with Cron at 1 meter look much like Jono's. I see a shift that peaks at f4 and diffraction kicks in at f11. After looking at Jono's results and mine, I'd say this lens favors the farther side of the DOF scale (like about 1/6 before, 5/6 after instead of 1/3 before and 2/3 after). If it backfocuses, it is no more than a centimeter, and think that it's accurate within a reasonable tolerance. I think the Lux is a little better at one meter, but still the focus point on my Cron is always inside the DOF, and appears sharp.

 

At 10 meters, everything is tack sharp---I detect no focus shift from either lens. Slight softness in the Lux at f1.4, f11 and f16. Slight softness in the Cron at 2.0, very slight softening at 11, more noticable at 16. Seems the Lux suffers a bit more from diffraction. The Cron appears to deliver slightly higher contrast and harder edges, a bit stronger bite.

 

I've also shot extesively in varied situations (near, far, many apertures) with the Cron for four years, and the Lux for one year. These are both fantastic lenses, and are not exhibiting the problems some folks are seeing, either under tests or in practical use.

 

Until later,

 

Clyde Rogers

[jonoslack]

 

My shots with Cron at 1 meter look much like Jono's. I see a shift that peaks at f4 and diffraction kicks in at f11. After looking at Jono's results and mine, I'd say this lens favors the farther side of the DOF scale (like about 1/6 before, 5/6 after instead of 1/3 before and 2/3 after). If it backfocuses, it is no more than a centimeter, and think that it's accurate within a reasonable tolerance. I think the Lux is a little better at one meter, but still the focus point on my Cron is always inside the DOF, and appears sharp.

 

At 10 meters, everything is tack sharp---I detect no focus shift from either lens. Slight softness in the Lux at f1.4, f11 and f16. Slight softness in the Cron at 2.0, very slight softening at 11, more noticable at 16. Seems the Lux suffers a bit more from diffraction. The Cron appears to deliver slightly higher contrast and harder edges, a bit stronger bite.

 

I've also shot extesively in varied situations (near, far, many apertures) with the Cron for four years, and the Lux for one year. These are both fantastic lenses, and are not exhibiting the problems some folks are seeing, either under tests or in practical use.

 

Until later,

 

Clyde Rogers

 

Thank you Clyde for describing my new lens so well ! Seriously, I've only had it for five hours, and your description does seem to describe it pretty succinctly. I'm really happy with mine, and it's so small and smoothe and neat.

 

I've just sent back a brand new 4xxxxxx serial number 90mm macro elmar for . . . . you guessed it, backfocusing badly. I wonder if Leica are actually having a calibration problem with some new lenses - it's beginning to look like it.

 

Tim - I think your description seems to cover your feelings about your 'cron - but does it account for your 'lux problems? They seemed to be much more of an issue at mid distances?

 

Here is a straightforward (but stormy) shot to celebrate my new lens:

 

M8, 35 cron asph (uncoded) f8 1/1500, no filter

 

[ho_co]

1) My opinion is still that this is an optical phenomenon and not a mechanical one. By that I mean simply that if your lens is working today, it will work after coding, barring human error in reassembling. Don't assume I'm right; certainly gathering data as Tim has suggested is the only way to come to a solution.

 

2) The rule-of-thumb for depth of field (1/3 : 2/3) is only approximate and applies only at 'normal' picture-taking distances. It varies continuously as one focuses closer, until at 1:1, DOF is the same on both sides of the focus plane.

 

3) The method Sean uses for testing focus shift is a good one and guarantees consistency. I doubt there is a better way for home testing. But remember that best resolution and best contrast come at different points in the ray cone, and we don't know where Leica chose to put its 'best focus' point along that cylinder.

 

4) I think it's beginning to be irrefutably clear that the phenomenon exists. Another possible suggestion as to why: Did Leica at some time during the production of the 35 Summilux a) receive a new batch of glass; switch to a new vendor for some of the glass; c) switch to a new subcontractor for some part of the assembly? Leica would normally double check to be sure the glass was to spec, particularly if going to a new vendor; but checking might seem less necessary if getting a new batch from a previously reliable vendor.

 

--HC

[tashley]

Hi Tim,

 

I'll need to check that. But there's a confounding issue here as well. Earlier I quoted from my own draft saying:

 

"This kind of focus bracketing is necessary for any resolution comparison because A) We're human and our eyesight is not perfect and Even the best rangefinder mechanism is a mechanical device with a finite amount of precision. There is also a tiny amount of play within the various mechanical pieces that link the lens to the rangefinder, etc. The M8 uses what is probably the highest quality rangefinder ever integrated into a small-format camera but one can still move a focus ring a tiny amount without disturbing the alignment of the rangefinder windows. The M8 is vastly better than the Epson R-D1 in this respect but it can't be perfect and so focus bracketing is needed for precise evaluation."

 

So, sometime a slight tweak of the focus ring in either direction is correcting for human error or mechanical tolerances, not necessarily for any misfocusing in the lens, per se.

 

More later.

 

Cheers,

 

Sean

 

Hi Sean,

 

I take that on board and I would certainly never lay into a lens on the basis of a few fuzzy shots, there's always the chance of the factors you mention being in play! But I do know that the huge majority of the time, my other glass gives good focus when I think I have nailed the RF, and it was educational that the Skopar satisfied right out of the box, whereas the cron is nearly always wrong unless I purposely pull focus forward. If there is that level of consistency then I am quite sure there's an issue with the lens.

 

I could send it to you, would be very happy to, but I suspect that would only prove one thing about one lens and I'm keen to sort out the wider issue of why so many 4***** 35's have 'issues'!

 

Best

 

Tim

[sean_reid]

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To provide another data point (and data for a recently coded older Lux ASPH), I just ran through a test of my two 35s (yeah, I'll get around to selling one someday...). Shots on tripod at 1 meter and at 10 meters, all full aperture stops (1.4, 2.0, 2.8, etc., through 16), ISO 160 DNGs.

 

The 35 Lux ASPH was coded at New Jersey in February, and the Cron ASPH is uncoded. Lux serial number 38895xx, Cron 38474xx.

 

With the Lux at 1 meter, I do see that slight backward focus shift at 2.8, and a more visible shift at 4.0. Diffraction shows an overall softening at f16. The focus point is always in the range of maximum sharpness. A top notch performance.

 

My shots with Cron at 1 meter look much like Jono's. I see a shift that peaks at f4 and diffraction kicks in at f11. After looking at Jono's results and mine, I'd say this lens favors the farther side of the DOF scale (like about 1/6 before, 5/6 after instead of 1/3 before and 2/3 after). If it backfocuses, it is no more than a centimeter, and think that it's accurate within a reasonable tolerance. I think the Lux is a little better at one meter, but still the focus point on my Cron is always inside the DOF, and appears sharp.

 

At 10 meters, everything is tack sharp---I detect no focus shift from either lens. Slight softness in the Lux at f1.4, f11 and f16. Slight softness in the Cron at 2.0, very slight softening at 11, more noticable at 16. Seems the Lux suffers a bit more from diffraction. The Cron appears to deliver slightly higher contrast and harder edges, a bit stronger bite.

 

I've also shot extesively in varied situations (near, far, many apertures) with the Cron for four years, and the Lux for one year. These are both fantastic lenses, and are not exhibiting the problems some folks are seeing, either under tests or in practical use.

 

Until later,

 

Clyde Rogers

 

That's roughly consistent with what I have seen from both lenses (35/1.4 Asph and 35/2.0 Asph) except that I see diffraction becoming noticeable with both lenses at about F/11. They both back-focus a bit at the middle apertures but its minor.

 

Cheers,

 

Sean

[sean_reid]

Hi Sean,

 

I take that on board and I would certainly never lay into a lens on the basis of a few fuzzy shots, there's always the chance of the factors you mention being in play! But I do know that the huge majority of the time, my other glass gives good focus when I think I have nailed the RF, and it was educational that the Skopar satisfied right out of the box, whereas the cron is nearly always wrong unless I purposely pull focus forward. If there is that level of consistency then I am quite sure there's an issue with the lens.

 

I could send it to you, would be very happy to, but I suspect that would only prove one thing about one lens and I'm keen to sort out the wider issue of why so many 4***** 35's have 'issues'!

 

Best

 

Tim

 

Hi Tim,

 

I think that common sense question is indeed important. If your other F/1.4 lenses all focus correctly on the M8 (using your eyes and your normal methods) it's natural to wonder why that 35/1.4 didn't. I don't have an answer for you about that, alas.

 

Cheers,

 

Sean

[Jamie Roberts]

The latest data points--coded new 35 ASPH Luxes working without an issue--do suggest, though, that there is a lens production problem somewhere in the chain, either on the adapter end or in the lens itself.

 

We're back to "it looks like a run of bad lenses" or it's a stellar coincidence on an individual number of bad lenses.

 

Either can happen, so the important thing is to make sure your dealer will let you check the lens out before you buy (or have a good return policy).

 

Now--I have a backfocusing 5d with a 50 1.2L I need to talk to Canon about

[scho]

The latest data points--coded new 35 ASPH Luxes working without an issue--do suggest, though, that there is a lens production problem somewhere in the chain, either on the adapter end or in the lens itself.

 

We're back to "it looks like a run of bad lenses" or it's a stellar coincidence on an individual number of bad lenses.

 

Either can happen, so the important thing is to make sure your dealer will let you check the lens out before you buy (or have a good return policy).

 

Now--I have a backfocusing 5d with a 50 1.2L I need to talk to Canon about

 

The DPR Canon lens forum is chock full of backfocusing lens issues. I'm sure they would love to discuss yet another.

[wparsonsgisnet]

... Here is a straightforward (but stormy) shot to celebrate my new lens: M8, 35 cron asph (uncoded) f8 1/1500, no filter

 

Jono, in your post above (#404) you say no filter. What color correction did you apply to this? Did you use one of Jamie's profiles?

 

Also, terrific detail from that lens. What aperture?

 

Nice backyard, btw.

[jonoslack]

Jono, in your post above (#404) you say no filter. What color correction did you apply to this? Did you use one of Jamie's profiles?

 

Also, terrific detail from that lens. What aperture?

 

Nice backyard, btw.

Hi Bill

Thank you - I added a very small point addition to the yellow hue for this shot (but I don't think it was necessary). I don't use C1 at all - did try, but I never could get decent colours for landscapes, and although Jamie's profiles are splendid for 'normal' stuff, I couldn't get it to work for my oddities.

 

This was processed in Aperture using Eoin's hack, with quite a boost to contrast and shadow detail and a small boost in saturation. I started with Aperture . . .dutifully used C1 for a month, went back to Aperture . . . . used Lightroom for 6 weeks, and now, I'm absolutely back with Aperture - I'm getting better results, and the workflow and printing suits me far better.

[castelletta]

So can those of you with troublesome 4**** crons try my test and report back?

Tim

 

I'm out of the "competition" now. No further tests with my 35 cron.

 

I visited today the italian Leica distributor to meet 2 techs and have them check my m8 + 35 cron.

 

They never saw a lens do what my lens do; the DNG samples were in front of all and spoke clear. Then the M8 and the lens were instantly sent to Solms.

 

PS: Like Tim I tested two weeks ago at my dealer another brand new 35 cron. Same as mine, for the bad.

[jonoslack]

I'm out of the "competition" now. No further tests with my 35 cron.

 

I visited today the italian Leica distributor to meet 2 techs and have them check my m8 + 35 cron.

 

They never saw a lens do what my lens do; the DNG samples were in front of all and spoke clear. Then the M8 and the lens were instantly sent to Solms.

 

PS: Like Tim I tested two weeks ago at my dealer another brand new 35 cron. Same as mine, for the bad.

Hi Roberto - did they need to take your body as well?

I hope it all comes back fixed soon - I've just been looking at your zenfolio site - wonderful stuff - congratulations

[ho_co]

According to http://www.leica-camera-user.com/digitalforum/20185-front-backfocus-mit-35mm-und-m8.html#post214155 this issue may be addressed by the May Issue of LFI. Does anyone have access to that?

Guido--

According to a thread in the German section, the magazine is available in shops and just beginning to arrive to home subscribers. No comments so far on this topic.

 

Tim--

If Roberto's techies said Solms would want to see both the lens and the body and that they had never seen any such thing, we're making progress! Give them ten minutes with Roberto's equipment, then send them yours as well. Seems peculiar that it might be body-related, but that's a possibility I think we had already rejected.

 

Problem should be solved quickly. At least before the R10 comes out.

 

Good luck to you both!

 

--HC

[ho_co]

We've been treeing the wrong squirrel. Consider this possibility:

 

It's not the lenses that have the problem, but the bodies; more specifically, it's the sensor.

 

The sensor in some bodies is bowed slightly forward in the center, so when the lens is wide open the center of the image falls behind the center of the sensor.

 

The way to check--send both lens and body to Solms; but that's no fun.

 

Quicker is: Find a person who is your opposite and swap lenses, using the other's lens on your body and vice versa.

 

(Tim--you've already had two Summiluxes that you gave up on even though Solms says they're okay, so you've done this half way already. Others have also tried the test on their own lens and also on a lens at their dealer's. What we need to do is move one step forward from there but eliminate the unknown.)

 

Person A is happy that his lens and body work just fine. Person B is unhappy that he has to fiddle to make lens and body work together. Okay: Person A and Person B meet and exchange lenses.

 

If Person A finds the lens borrowed from Person B just fine, and Person B finds that the lens he borrowed from Person A isn't any better than his own lens, the problem is in Person B's body, and is likely the sensor since that's the only part that could get bent (besides Person .

 

On the other hand, If Person A tries Person B's lens and it's just as bad on Person A's body as it was on Person B's body, then the problem is with Person B's lens and Person A better have let the air out of Person B's tires to prevent his absconding with Person A's lens. In this case, this conjecture is invalid, but at least we know it's the lens.

 

Thank you, Jamie, for continually stressing that it might be a bad batch of something--lenses, bodies, lens mounts! And thank you Roberto, for saying Solms was unaware of this issue and wanted both lens and body!

 

Now while you guys ponder why it took us 400 posts to decide it was a defective body (read: a batch of defective bodies), I'm going back to bed.

 

This won't need a recall, though, if I'm right. Just a little thumb pressure against the center of the sensor should do it. Need to remove the IR-absorptive cover glass first, of course, and replace it after bending the sensor back into place. (We don't want to lose what little IR filtration the M8 has, because the filter/firmware solution is based on the presence of that filter.) I'll work on that technique tomorrow. Man, we're lucky the M8 has a divided sensor! That'll make it easy to bend it back into place. Oh, and the off-axis sensor lenses: My sources say they're just stuck on with static electricity, so if we nudge them off center a bit, they'll be easy to replace. As a matter of fact, that's why some people have found that the M8 is a bit dust-sensitive.

 

And yes, I'm serious about all of this post except the sensor-bending part.

 

--HC

[castelletta]

Hi Roberto - did they need to take your body as well?

I hope it all comes back fixed soon - I've just been looking at your zenfolio site - wonderful stuff - congratulations

 

Yes Jonathan, both. There may be problems with either of them.

 

Thank you very much for the appreciations for my portfolio; when my camera allow it (not all time if it's an M8 ) I love to take pictures.

 

It's not the lenses that have the problem, but the bodies; more specifically, it's the sensor.

 

The sensor in some bodies is bowed slightly forward in the center, so when the lens is wide open the center of the image falls behind the center of the sensor.

--HC

 

Wow! I've never thought of such a terrifying chance (to have the CCD bowed). But I have to admit: it does make sense.

 

BUT

 

I remember that Tim had no problems at all with other lenses than 35 and 28mm.

So there can be some evidence that only this very focal length range (28-35mm) exacerbate the effects of a sensor bowed in the center?

 

Please techs, come on and tell us if it can be a possibility.

[tashley]

We've been treeing the wrong squirrel. Consider this possibility:

 

It's not the lenses that have the problem, but the bodies; more specifically, it's the sensor.

 

The sensor in some bodies is bowed slightly forward in the center, so when the lens is wide open the center of the image falls behind the center of the sensor.

 

The way to check--send both lens and body to Solms; but that's no fun.

 

Quicker is: Find a person who is your opposite and swap lenses, using the other's lens on your body and vice versa.

 

(Tim--you've already had two Summiluxes that you gave up on even though Solms says they're okay, so you've done this half way already. Others have also tried the test on their own lens and also on a lens at their dealer's. What we need to do is move one step forward from there but eliminate the unknown.)

 

Person A is happy that his lens and body work just fine. Person B is unhappy that he has to fiddle to make lens and body work together. Okay: Person A and Person B meet and exchange lenses.

 

If Person A finds the lens borrowed from Person B just fine, and Person B finds that the lens he borrowed from Person A isn't any better than his own lens, the problem is in Person B's body, and is likely the sensor since that's the only part that could get bent (besides Person .

 

On the other hand, If Person A tries Person B's lens and it's just as bad on Person A's body as it was on Person B's body, then the problem is with Person B's lens and Person A better have let the air out of Person B's tires to prevent his absconding with Person A's lens. In this case, this conjecture is invalid, but at least we know it's the lens.

 

Thank you, Jamie, for continually stressing that it might be a bad batch of something--lenses, bodies, lens mounts! And thank you Roberto, for saying Solms was unaware of this issue and wanted both lens and body!

 

Now while you guys ponder why it took us 400 posts to decide it was a defective body (read: a batch of defective bodies), I'm going back to bed.

 

This won't need a recall, though, if I'm right. Just a little thumb pressure against the center of the sensor should do it. Need to remove the IR-absorptive cover glass first, of course, and replace it after bending the sensor back into place. (We don't want to lose what little IR filtration the M8 has, because the filter/firmware solution is based on the presence of that filter.) I'll work on that technique tomorrow. Man, we're lucky the M8 has a divided sensor! That'll make it easy to bend it back into place. Oh, and the off-axis sensor lenses: My sources say they're just stuck on with static electricity, so if we nudge them off center a bit, they'll be easy to replace. As a matter of fact, that's why some people have found that the M8 is a bit dust-sensitive.

 

And yes, I'm serious about all of this post except the sensor-bending part.

 

--HC

 

Howard, Nice Try!But I fear that Occam's razor is now being used to cut the grass... let's not forget that I have two M8 bodies with widely different serial numbers, that Jono and I have swapped lenses, and that my CV35, CV15m, WATE, 24 elmarit, 50 lux and 90 elmar all focus correctly on centre on both my bodies.

 

It's not the body. Trust me. And I do believe that I have the squirrel up the tree, I just need to avoid it crapping in my eye while I wait for someone with a gun!

 

Best

 

Tim

[ho_co]

Ah, gee!

 

Roberto, Tim--my bad.

 

You're right, of course. Cameras work with other lenses, you've already done the swap, the lenses don't work on any camera.

 

Tim, I knew there was a reason the Brits hunted foxes instead of squirrels! Looks like I got it in my eye instead.

 

Oh, well. I'll get out of the way for a while.

 

--HC

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Hallo,

Look here: Interesting Leica gear

[wparsonsgisnet]

... And yes, I'm serious about all of this post except the sensor-bending part.--HC

 

Whew, that's a relief. I was thinking the owner would have to have a green (er...magenta) thumb.