Do I have front focus m9 issues? Or is it my lens? Help please...

[jaques]

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I noticed recently that the focus on my CV35 1.4 seemed to be out a touch. I tested it against my summicron 50 and both lenses seemed to be front focusing wide open at the minimum focus distance.

 

I did some testing with a range of lenses wide open, and at f8. I obviously didn't do a good job of lining up my test chart... however on all lenses it seems the best focus was just in front of where it should be. I am not sure if you can tell much from the f8 tests at that distance- I should have gone 5.6...

 

I am wondering if anyone experienced can make anything of these test images for me. Do you see any RF issue from the camera? The CV lens is obviously out- but the other lenses seem to be to me as well- though it gets less as the focal length increases.

 

A penny for your thoughts and diagnosis- I focused on the edge of the little stone which was lined up with the center of the test line.

 

the photos are respectively

 

CV 35 1.4 @f1.4

CV 35 1.4 @f8

Summicron 50@ f2

Summicron 50@f8

Elmarit 90@ f2.8

Elmarit 90@f8

Elmar 135@ f4

Elmar 135@ f8

 

I hope these images are not too small to tell anything?

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[jaques]

Ok- I think those images are too small- here are crops of the lenses wide open (in the same order: CV35, S 50, E 90, E 135 ignore the filenames)

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[Knorp]

Jacques, I agree that the camera is front focusing. However I think your test setup with this pebble is flawed and can't give you accurate results. Focusing on a point elevated from the black line will always show a tendency to front focusing, because you're shooting under an angle. But my M9 was also front focusing and had to be sent back to Solms for adjustment. So sorry ...

 

All the best.

[jaques]

I did some shots without the pebble at the start- and they showed the same tendency. I realise the elevation of the pebble would throw the focal plane forwards a few mm- but I took care to focus from the centre line of the pebble- and the black line below. The pebble helped to focus and made the test more interesting.

 

My test was flawed for sure- but looking at my enlargements the shift seems fairly constant- around 10mm in front.

 

Would that much front focusing justify a trip around the world? I am in australia... :-(

[cliffp]

I had exactly the same problem. My camera and lenses are at Solms at the moment. It definitely needs to go back in my opinion. I would also send back all of your lenses - they will adjust them all to be perfect with your camera free of charge. I managed to get Leica UK to pay to collect my gear. When packaging the lenses I would remove all filters and lens hoods but leave on the caps of course. I used the leather pouches and even put them in the boxes for protection. There is another thread where people are talking about cosmetic damage being done to lenses - you could take photos of your lenses for eveidence if they come back damaged (a bit paranoid maybe but it would make it easier if you did have issues)

[jaques]

Thanks for the tips Chris- I hope you get your camera back quickly.

 

I am guessing Solms won't adjust my CV nokton to perfection? ;-)

 

which is a shame as it is by far the least sharp of the 4 lenses I tested. The summicron is the clear winner but all the Leica lenses look sharp at least. All the Leica glass is vintage and second hand- but in good order- will Leica adjust my 73 Summicron, etc?

 

I have been thinking that my focusing is out- even though I have perfect eyesight still... but it looks like the RF is out. How hard is the adjustment- and is it very different than on a film M? I have a very good Hasselblad and Leica trained tech living only a few blocks from my house. He was trained in the microscope department at Solms but has worked on M's and every camera imaginable. He was fully trained as a camera tech at Hasselblad and also worked at Linhof. He recently did a great job repairing my M6 rewind knob and cleaning the RF. He has a collimator, etc and told me he can adjust all m lenses. Would a service from a tech do anything to the Leica warranty?

 

 

Oh- and I just wanted to clarify something about the pebble: it is actually quite flat- almost like a little arrow head- it only overhangs the focus line by a few mm...

[ArtZ]

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Jacques,

 

There're a few things I'd like to share with you.

 

1.- Front focus at closest focus distance may happen with some lenses, especially with ASPH lenses. The "problem" is often the lens, not the camera. Usually front focus at 0.7m is corrected by DOF, so you shouldn't worry to much about it. But if front focus is too important, you should send the lens (and the camera) to Leica to correct it. To check this, I like this DOF online calculator Online Depth of Field Calculator

 

2.- When you test focus on a lens, the black line where is written "FOCUS HERE" should be completely horizontal and parallel to the camera (180º). If it goes to the right (<180º) or to the left (>180º), or one side (left or right) of the camera is closer to the Focus Chart than the other, the image will show different values on each and the test won't be very accurate. The camera has also to be inclined at 45º.

 

3.- I have 4 Noktons (I had two more) and all of them are spot on. Hereunder you will see a focus test with the CV 50/1.1 done last Sunday.

 

TIP: Instead of taking the picture with the camera at 45º, you can also set the Focus Chart Test @ 45º !!!

 

Yes, I have a jpg of the Focus Chart in my laptop. For a quick check of a lens (even when you buy one), I just need to fit the laptop screen at 45º and shoot in front of it. I can even hold the camera with my hands, because my computer LCD will produce enough light to take the picture at least at 1/250. This is how the focus test of the Nokton 50/1.1 has been taken. Notice that the right side of the camera was a bit closer to the laptop LCD than the left side, so the values on the left side are slightly different than on the right side.

 

 

. <-- 0.7 / 1m @ 45º -->

\

.\ . . . . . . . . . . . . . . . .o=[]

..\________ . . . . . . . . . ./ \

----------------------------------- / . \

. . .(laptop) . . . . . . . .(camera)

 

Hope that's help!

 

 

PS: I have added also cropped image of my CV Nokton 35/1.4 focus test (last image)

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[jaques]

I understand my tests was not conducted ideally- however the camera was on a tripod, focused carefully, and set at 45 degrees... and tested at various apertures. The focus shift is always to the front. I am sure what I am seeing is not caused by the poor positioning of the paper. There is no part of the line that is in focus. Looking at your images makes me feel certain there is a problem with my RF.

 

Indeed I could only get the line in focus wide open was by focusing on a rice bubble 1cm behind the line:

 

 

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[ArtZ]

Jacques,

 

That's fine. Your camera is OK.

.

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[jaques]

You think the RF is spot on? I hope you are right and I am just paranoid and sloppy in my testing.

 

But how do you explain the images above? The first is the CV focused exactly on the line- yet the line is outside the acceptable area? The stone is quite fuzzy? The last one (summicron 50) posted shows the depth of field very close to the focus line- yet the camera was focused 1cm behind that point on the rice bubble which is not in focus. Even taking into account the total DOF (3.7cm) it seems my RF must be out? Also how do you explain the universality of my focus shift? Or is this variation within tolerances?

 

So far I have two votes for front focus issue and one against....

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[jaapv]

As pointed out, focussing on the pebble makes the test invalid. That will produce a slight front focus. Given that just that is happening here makes me think that your camera is fine. in one shot, btw, nothing is in focus. Are you doing this hand-held?

[jaques]

hmm, here we go. I knew the pebble would kill me. I got the same result without the pebble- I just used it in the second round of tests as a focusing aid- and as I stated already the pebble is quite flat with its center line aligned with the line it sits on. In addition to focusing the edge of the pebble I kept an eye on the edges of the black line and focused very carefully on it. At most that pebble could move the focal point forwards by 2mm (which I doubt very much) yet the focus seems to have shifted around 1cm? And at the least even if the test sheet is out: shouldn't the pebble be in focus?

 

the last image is not of a pebble but a rice bubble- very small- and I actually focused on the leading edge of the shadow- which is on the paper and nearly one CM behind the black line. Yet the rice bubble is not in clear focus?

 

The shot that is totally out of focus is probably the 35 nokton wide open- and it a closer crop- the front focus seems the worst on that lens and I am wondering if it has issue of its own that heighten the problem. I used a tripod on all these shots and the self timer.

 

I will do a few more without the pebble with the 50 summicron.

 

I will do a more thorough and scientific test, although I feel sure the result will be the same. I did around 30 shots and I never had one with back focus- and not one where it seemed the focus was spot on where I had aligned the RF patch. I am just wondering if this degree of calibration is acceptable?

[Guest trond]

Dear Jaques,

 

You should use a vertical high contrast target for focusing, combined with a ruler for measuring focus error.

 

Se my posting in the ling below:

 

http://www.l-camera-forum.com/leica-forum/leica-m9-forum/111918-m9-lens-focus-setting-2.html#post1225856

 

Best regards

 

Trond

[Julian Thompson]

I too believe that your shots show front focus.

[Guest mc_k]

you are shooting at 45 degrees--if you aim at something a certain height above the chart, focus will be displaced forward by the same amount.

 

There is space just outside the box to draw a little cross to focus on, which many have done.

[jaques]

Thanks for all the opinions everyone... I understand that the pebble is raised above the paper- but as I have already said- I only believe it could throw the focus forward by 2mm at most- and in any case at the very least the pebble itself should be in focus- which it isn't?

 

I will repeat the test for the purists- but I think the result will be the same.

[Julian Thompson]

Jaques - also, to suppliment your work here why not go and shoot a few images of high contrast, easy to focus things at a range of distances with something reasonably telephoto.

 

Remember that as you twist the lens from infinity to close focus the focus 'comes' from the back to the front. So if you want to nudge the focus backwards in a front focussing camera you need to fire off the shot just BEFORE the image in the rangefinder goes high contrast. Do two shots of each thing - the first with the focus deliberately nudged like this and then the second with the rangefinder perfectly in contrast. You can compare the results when you get home and this might assist in looking at the focus chart with some additional evidence.

 

Funnily enough I found it easier to tune my camera using real-world shooting than by using the focus chart so you may find the same to some extent.

[cliffp]

I would second what Julian says re: real world shooting. I sometimes struggle to focus indoors on a test chart whereas if you go outside and find a suitable object with some sharp features you may well have far more confidence that you have definitely achieved the best focus. I have found some flowers to be good but with the downside that you need to remember precisely which part of it you focussed on. My recent favourite has been a brick wall - it has plenty of contrast and if you shoot it head on, there isnt more than a few millimeters of depth to add uncertainty to the focussing point.

[ArtZ]

I would second what Julian says re: real world shooting. I sometimes struggle to focus indoors on a test chart whereas if you go outside and find a suitable object with some sharp features you may well have far more confidence that you have definitely achieved the best focus. I have found some flowers to be good but with the downside that you need to remember precisely which part of it you focussed on. My recent favourite has been a brick wall - it has plenty of contrast and if you shoot it head on, there isnt more than a few millimeters of depth to add uncertainty to the focussing point.

 

Cliff,

 

Shooting a brick wall to test focus you may get wrong results. As you said "there isnt more than a few millimeters of depth to add uncertainty to the focussing point" and the distance from your camera to the focus point is smaller than the distance from your camera to the corners. The result is you will always get corners out of focus... and as lenses wide opened tend to have soft corners, that will make this test not valid.

 

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Hallo,

Look here: Leica M

[cliffp]

Surely you make your judgement about the focussing accuracy by looking only at the centre?