Very interesting answer from Leica on 35mm 1.4

[Jamie Roberts]

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Sergio is exactly correct, IMO.

 

Also, as far as Puts goes, this is what he had to say about the 35 Lux ASPH:

 

"At full aperture the 35 mm Summilux ASPH delivers a high contrast image

with excellent micro-contrast and a crisp rendition of very fine details in the

center and over a large part of the field. Extremely fine details are clearly visible

but they show soft edges, which reduces this lens’ ability to record smoothly graded illumination differences. Light fall-off is noticeable, but restricted to a very small zone.

 

Flatness of field is outstanding and distortion just noticeable. Centering proved to be

perfect.

 

At f/2 the overall image quality improves with slightly higher contrast for

the fine details over most of the image area. The finest details are recorded

very cleanly with crisp edges. At f/2.8 there is a small improvement over the

whole image field and at f/4 the performance peaks at a very high level."

 

Doesn't sound like it's mis-focussing due to curvature of field to me...And I don't think any amount of "the sensor isn't as flat as film" argument holds any water whatsoever. If that were true--NONE of the luxes would focus at all

[ho_co]

I took a whole load of shots for fun this afternoon and my new CV35 is a doll. Bit smeary on the far left, not so as you'd notice, but otherwise very much sharper on centre than the cron.

Now there you've spilled it: That's two lenses you've got that are slightly unsharp on the left.

 

There is almost certainly a misalignment with the body, either the lens flange or the sensor.

 

I waxed so elegant (what, me long-winded? ) above that I'm not going to go back and figure out what parts to retract, but I think you definitely need to have the body checked with the 24.

 

And then Leica can link to your Venice shots with the note, "See what Tim Ashley did with a defective M8."

 

I'm off to Barcelona for the weekend and I will get back to the real job in hand - taking pictures!

Damn you guys in the Old World! Just traipsing off for the weekend to Barcelona, is it? Rub it in, will you? It takes me as long to get to Dallas as it takes you to get to Barcelona!

 

Have a good trip and let us see the results! (Particularly Lars)

 

--HC

[wparsonsgisnet]

Let's see: Barcelona; Dallas. Barcelona; Dallas.

 

How long? Where's my bag?

[ho_co]

@Jamie--

Since the birdhouse example refers to the 35/2, I posted the above Puts link comparing the Biogon and the Summicron. There he says:

"[in the Biogon] ... at full aperture there is a fair amount of coma, but hardly any curvature of field. The coma does reduce the overall contrast quite visible. At f/4 coma is gone completely and the lens from there is an outstanding performer. Compared to the Summicron-M 2/35 ASPH the ZM has better curvature of field, but less contrast and crisp definition wide open. Performance on axis is equal between both lenses. This Biogon is a bit overstretched as a high-speed design."

 

I certainly didn't intend to raise your hackles. You and I are both trying to find the solution to Tim's problem, and I'm glad to be corrected. When I throw out ideas based on my understanding of a situation, I'm not being autocratic; I'm simply saying what I see.

 

You say: "I don't think any amount of 'the sensor isn't as flat as film' [sic] argument holds any water whatsoever. If that were true--NONE of the luxes would focus at all."

 

If you mean it doesn't hold water in this case, you may be right. As you see above, I'm changing my mind to agree with you that this is beginning to look very definitely like a camera problem.

 

On the other hand, the 'sensor is flatter than film' argument is pretty generally accepted. Both LuLa and E Puts make reference to it as a given. But be that as it may, I don't see the logic in your conclusion that no Summilux would focus if the argument is accurate.

 

In regard to flatness of field, EP has spent some time on the fact that Leica has designed its lenses with the expectation that film will bow forward (I think) from the camera's 'film plane,' while Zeiss designs assume that the film will bow the opposite direction.

 

At the moment, I can't cite sources for these points, and I've listed them as I recall them, though my recollection may be spotty or incorrect.

 

I mean all simply as an attempt to help solve the problem.

 

@Tim--

I think Mark's suggestion above is quite important: You've focused on the birdhouse, then shifted it to the left. Do the same, but shift the frame to place it to the right as well.

 

You've said that two lenses are fuzzier on the left than on the right. Now you've shown a very interesting focus shift from center to left; is it the same from center to right?

 

--HC

[marknorton]

Yes, a fab place to visit. Last year, I went there for something silly like $20 each way + taxes. Just watch the Leica on Las Ramblas!

[sergiolov]

Howard,

as I pointed in my previous post, the focus an reframe procedure used by Tim lends to incorrect result, for mere geometric relations, due to the fact that rotating the camera you are rotating the flat focus plane also. This is a not so known situation.

Sergio

[Jamie Roberts]

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@Howard--stupid airport network ate my long reply!

 

Anyway--no hackles raised--and no worries; I know we're all trying to help Tim!

[wlaidlaw]

Yes, a fab place to visit. Last year, I went there for something silly like $20 each way + taxes. Just watch the Leica on Las Ramblas!

 

I am going to be in Barcelona middle of next week - first time since racing in Montjuich Park in 1968. I have heard horror stories of the thief gangs but wondered if it was being exaggerated. How bad is it? Any advice appreciated.

 

I have heard about the dodge with the knife in the tyre at traffic lights and 295/30 x 18's don't come cheap, let alone the hospital bill for getting repaired after the mugging you receive when you exit the car to investigate. I have therefore arranged to leave my car at the Porsche garage on the outskirts for the two day duration of my stay and I will use taxis.

 

Wilson

[marknorton]

We stayed centrally and walked everywhere; got accosted by gypsies once, you just need to keep your wits about you. Fabulous place to visit.

[tashley]

Tim, I got curious and took the attached pix:

 

35 'lux asph, closest focus, f1.4, 1/125, iso 160, nothing else; then, f5.6, rest the same.

This was focused on the edge of the paper, at the center of the pic. The 31 and the scribble are in the same plane of focus.

 

The 1st is at f1.4; the second, at f5.6.

Both are in v1.092, with Edmund LoSatTuned2 profile, and WB. No other processing.

 

 

Bill, thanks for running this. What do you take from it? To me, the 5.6 shot shows focus shift backwards. If you did it at f4 I suspect it would look worse?

 

Best

 

Tim

[tashley]

Hi Tim,

a few points. First the mistery of the bird box.

The focus and reframe procedure is usually misunderstood. A lens focuses a plane on another plane, not a sphere. So the focus distance is valid only for objects that are perpendicular to the sensor. Remember Pytagora theorem? If your focus distance is 10 meters perpendicular to the focus plane, an object displaced 10 meters on that same plane will be on focus, but its distance from the focus plane will be 14,14..meters.

If you put this on a drawing, you'll see the consequences..

 

Also, did you take a look to the MTF table for the lux asph, as I suggested in my preceding post? You'll notice that the 40 lp/mm line at 2,8 is strongly sinusoidal, with a variation of more than 2 stops. This accounts for a sharpness variation across the frame.

 

The question of the lens and the opinions of the guy in Solms. What he declares is only generically correct, but has no relation with the case we are discussing here.

It is completely true that the lens backfocuses when stopped down. The question is if it is possible to maintain the focus plane inside an acceptably sharp area while focusing and stopping down. If this is possible even with one lens, than all others are practically misadjusted.

Now we know that my lens and a few others focus with reasonable accuracy. I showed on my test that this is due to the fact that, with the lens full open the focus plane is positioned to the extreme rear position of the sharp area, while stopping down this plane progressively comes nearer to the front position of the sharp area. This is a good compromise, but is connected to the positioning of some shims that millesimally change the focus distance of the lens, as pointed by Brown.

And we also know that it is possible that, ignoring the opinions of that smart person from Solms, the operator and his Quality Control are sometimes a little distract.

Your "sharpness with focus guessing" is just like changing the thickness of a little shim.

I know that this is of no help, and that you want a working lens.

Ciao.

Sergio

 

Of course it is of help! But if you return two and get the same answer and then buy a third, what can you do?

 

Still, it's all quite interesting. When the manufacturer tells you it doesn't work and the a fair proportion of users say the same, you have to look at all the possibilities and it is remarkably difficult to ex-out possible factors one by one. I've tried three lenses on three bodies, all the same. Others have perfectly functioning examples. Or do they?

 

:-)

Tim

[tashley]

Now there you've spilled it: That's two lenses you've got that are slightly unsharp on the left.

 

There is almost certainly a misalignment with the body, either the lens flange or the sensor.

 

I waxed so elegant (what, me long-winded? ) above that I'm not going to go back and figure out what parts to retract, but I think you definitely need to have the body checked with the 24.

 

And then Leica can link to your Venice shots with the note, "See what Tim Ashley did with a defective M8."

 

 

Damn you guys in the Old World! Just traipsing off for the weekend to Barcelona, is it? Rub it in, will you? It takes me as long to get to Dallas as it takes you to get to Barcelona!

 

Have a good trip and let us see the results! (Particularly Lars)

 

--HC

 

HC, am sorry to burst an interestingly shaped bubble but the CV is actually slightly smeary on the right and the elamarit on the left. I transposed when typing, sorry! But I took these two obesrvations as a precise disproof of the theory that the sensor is misalinged. And my other lenses are smeary at neither side!

 

As for Venice - the thing that really p*** me off was that so many of the best shots were on the 35 lux, after I had worked out that I had to adjust focus beyond what the RF proposed. I would murder for one that agreed with my RF!

 

Barcelona here I come, and I'm NOT spending the weekend in a hotel room with a ruler and a tripod.

 

Lord that sounds kinky!

 

Best

 

Tim

[rosuna]

I am going to be in Barcelona middle of next week - first time since racing in Montjuich Park in 1968.

 

Woody Allen will be filming in Barcelona very soon (with Penelope Cruz, Javier Bardem and Scarlett Johanson).

 

A few weeks ago I went to the Bellas Artes Club Cinema to see "The Passenger", Antonioni's wonderful movie also filmed in Barcelona (30 years ago).

 

Please, upload some pictures here.

[tashley]

Woody Allen will be filming in Barcelona very soon (with Penelope Cruz, Javier Bardem and Scarlett Johanson).

 

A few weeks ago I went to the Bellas Artes Club Cinema to see "The Passenger", Antonioni's wonderful movie also filmed in Barcelona (30 years ago).

 

Please, upload some pictures here.

 

 

I will - and they WILL be in focus ;-)

 

Tim

[tashley]

Sergio is exactly correct, IMO.

 

Also, as far as Puts goes, this is what he had to say about the 35 Lux ASPH:

 

"At full aperture the 35 mm Summilux ASPH delivers a high contrast image

with excellent micro-contrast and a crisp rendition of very fine details in the

center and over a large part of the field. Extremely fine details are clearly visible

but they show soft edges, which reduces this lens’ ability to record smoothly graded illumination differences. Light fall-off is noticeable, but restricted to a very small zone.

 

Flatness of field is outstanding and distortion just noticeable. Centering proved to be

perfect.

 

At f/2 the overall image quality improves with slightly higher contrast for

the fine details over most of the image area. The finest details are recorded

very cleanly with crisp edges. At f/2.8 there is a small improvement over the

whole image field and at f/4 the performance peaks at a very high level."

 

Doesn't sound like it's mis-focussing due to curvature of field to me...And I don't think any amount of "the sensor isn't as flat as film" argument holds any water whatsoever. If that were true--NONE of the luxes would focus at all

 

Jamie, I read that too but it's dated 1997... and as a later post suggests, there are different assumptions about film bowing forwards/backwards. I am now up to 110% certain!

 

Tim

[tashley]

All the same scene, full sized 70% quality jpeg from DNG in Lightroom with defaults.

 

The first: 24mm elmarit at f4, shows smearing on the left

http://tashley1.zenfolio.com/img/p199625877.jpg

 

The second: 35mm CV pancake at f4 shows good centre sharpness and smearing on right

http://tashley1.zenfolio.com/img/p370426368.jpg

 

The third: 35mm 'cron, shows no smearing anywhere but is subtly OOF in centre

http://tashley1.zenfolio.com/img/p298907700.jpg

 

So if the Elmarit smears on the left and the CV on the right, they are both mildly knackered, just liveable with IMHO, but demonstrating that my M8 is not out of whack.

 

What other conclusions do people choose to draw? I conclude that I really really like my 50 lux! Look, she's almost smiling!

http://tashley1.zenfolio.com/img/p799869771.jpg

 

Best

 

Tim

 

ps anyone who says moire to that last one will get shot for being even more anal than me....

[scho]

My 35 biogon is uniformly sharp across the frame.

http://www.pbase.com/scho/image/75458099/original

[tashley]

My 35 biogon is uniformly sharp across the frame.

http://www.pbase.com/scho/image/75458099/original

 

 

That may be beautiful Carl, but you have no idea how irritating it is...

[egibaud]

The focus and reframe procedure is usually misunderstood. A lens focuses a plane on another plane, not a sphere. So the focus distance is valid only for objects that are perpendicular to the sensor. Remember Pytagora theorem? If your focus distance is 10 meters perpendicular to the focus plane, an object displaced 10 meters on that same plane will be on focus, but its distance from the focus plane will be 14,14..meters.

 

This is exactly why I did not notice the problem at first. As I had only ONE lens, I used it took take pictures of friends and family. I normally place the subject in a corner, 1 third or 1 quarter of the pic with maximal aperture 1.4 or 2.0 .... so I focused the subject and then reframed, my subject was perfectly sharp and the back ground (center of pic) out of focus, logically as it was the way I framed the pic. When taking the pic let's say with a subject 1 meter away, when I focused on the subject 1 meter away the RF showed focus, then I reframed... subject was now 1.2 meter away and was still SHARP.... Why? because when I focused before reframing, the RF was lying to me saying ;-) real focus spot was actually 1.2 meter away

 

Then when we started testing the lens, I was no longer reframing: results = center blured, corner sharp... Because then I was no longer get benefit from the back focus.

 

I am postive many have this problem.

 

A very simple test is:

 

1- place a tabloid news paper double page on a wall.

2- set your camera on a tripod with cam at horizontal and vertical level, framing to feel the camera frame with the news paper.

3- check the pic on you computer.... what is sharper? center or borders? what can you read best?

 

We did the test with 35lux, 35cron, 50cron, 90Elmarit, 90 tele elmar, 135Elmarit

 

They we all in focus except the 35Lux. This does not mean that the softer center of the Lux does not correspond to what somepeople want..... but for it is a 2500 Euro softness.... the CV35 is a 500 Euro sharpness :-)

 

Anyway I would not surprised to see new lenses appearing soon, Leica came up with the 28 Elmarit with the "excuse" to match the legendary 35 angle.... or because they are aware that they need to rethink a new line of lenses????? why do they remove the 75lux...?

 

Eric

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Hallo,

Look here: Interesting Leica gear

[ho_co]

Settle in with a glass of wine and check me out on the following :

 

... as I pointed in my previous post, the focus an reframe procedure used by Tim lends to incorrect result, for mere geometric relations, due to the fact that rotating the camera you are rotating the flat focus plane also. This is a not so known situation.

Sergio--

I agree completely, but that is beside the point that Mark and I were making. Obviously I didn't explain clearly, so I’ll try to be less oblique here.

 

First:

Whether we consider the geometry or not, we should see the same difference in focus when shifting from center to left as we see when shifting from center to right.

 

If we find a different shift of focus when swinging 17° left as compared to swinging 17° right, then we have a camera or lens problem.

 

In other words, whatever the shift of focus is, it should be symmetrical about the lens axis.

 

Second:

Indeed, the way the 'reframe procedure' is usually described, it is recommended that one "focus on another object at the same distance as the subject." If one does this, there are no geometric repercussions because both objects are the same distance from the camera: Focus on one object 10 m away, then turn and take a picture of another object also 10 m away.

 

Third—and here is where our friend Mr Pythagoras and your calculations enter the fray:

As I understand it, Tim wasn't trying to reframe by focusing on one object and then changing the subject. He focused on the birdhouse, then shifted the camera to put the birdhouse to the side of the frame. The edge of the sensor would have moved rearward a couple millimeters, changing the actual distance by that amount.

 

That is: Tim focused on the birdhouse at, say, 10 m. He then rotated the camera by about 17°. He was still 10 m from the birdhouse, but because he had turned a bit, the sensor has changed angle. So we're looking at this situation:

 

Distance from center of sensor to birdhouse when focusing: 10 m

Displacement of birdhouse from center to edge of sensor: ca 10 mm

Rotation of sensor: ca 17°

Displacement of sensor area now receiving image of birdhouse: ca 3 mm further from birdhouse

 

Since I don’t have focus formulas handy, I did a quick calculation of DoF.

 

Assuming:

CoC = 0,002 mm

distance = 10.000 mm

focal length = 35 mm

f-stop = 4

 

Then total depth of field is 1311,72 mm.

 

Same assumptions, except the distance to the birdhouse is now 3 mm further after rotating by 17°:

CoC = 0,002 mm

distance = 10.003 mm

focal length = 35 mm

f-stop = 4

 

Then total DoF is 1312,51 mm, an increase of 0,79 mm.

 

Please correct any of my math. It’s been a while since I played with geometry. The basic assumptions I made are these:

width of sensor = 24 mm; assume 10 mm for lateral birdhouse displacement

fov of 35 mm lens across 24 mm width = 37,85°; assume rotation of 17°

sensor rotation = 17°, half-angle = 8,5°

tan(8,5°) = 0,15, making the side opposite ca 1,49 mm; doubling this gives:

displacement of sensor at 10 mm = ca 3 mm rearward

If my math is correct (there’s at most an outside chance that it is ), then with these assumptions the difference in DoF implies to my mind that there would be little chance of seeing any focus shift due to rotating the camera through this short angle.

 

 

 

I’m glad you brought up the issue, Sergio, because I had never considered it and it is clearly something that must be recognized.

 

BTW, I really like your phrase “the mystery of the bird box.” There's a charm and playfulness in it. Your analysis of the lens adjustment also seems spot on.

 

There is one place where I believe Dale and you may be in error in regard to the lens assembly, but you may have put your finger on the source of Tim’s problem.

 

As I understand it, the focusing helicoid has a thread on both sides, and acts as a differential between the focusing ring and the lens head. Thus the outside of he helicoid may be cut the same for all lenses of a given design, but the inner thread is cut specifically for focal length variations. Leica previously did exactly this for lenses 50mm and longer, and never used shims. For that reason I doubt that they shim the wideangles.

 

Today I believe most if not all Leica lenses are labeled as having their design focal length. E Puts says that Leica's tight design standards make variances from plan virtually impossible. That is, the lens assembly is a go/no-go procedure: The assembly itself is part of the quality control.

 

Now if some tolerance is allowed in the optical units of wideangles but they are all mounted in the same helicoid, that could explain the differences between Jamie’s, Mark’s, Eric’s and Tim’s experiences. (And I think that's what we're searching for at least until Tim returns from Barcelona.)

 

Just an idea, following up on your suggestion that Leica use shims. Only a possibility, and one I tend to discount.

 

BTW, I believe that instead of using shims to adjust lenses, Leica simply adjusts the optical unit forward or back in the focusing mount, as Dale also mentioned.

 

--HC