new backfocus thread-solution

[JHAG]

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It's really becoming a rubik's cube.

I tweaked the backfocussing (main offender was my 35 summilux ASPH).

Now the situation is :

- all lenses are slightly front-focussing fully open (Noctilux, 35 Lux ASPH, 50 Lux preASPH)

- all lenses are almost spot on at 4-5.6 ( very slightly backfocussing : about 3 mm on the Leica chart)

- problem I do a lot of portrait, and I have now the focus on a strand of hair or on the eyebrows rather than the eyes…

- I don't know if any tweaking the cam will do

- I'm in the US next month and was thinking of sending everything (M8 + 3 lenses) to DAG.

- A question there : if I send it through Fedex from Europe to the US, then pick it up from DAG, will Fedex charge me some import tax in the US ?

[Jamie Roberts]

It's really becoming a rubik's cube.

I tweaked the backfocussing (main offender was my 35 summilux ASPH).

Now the situation is :

- all lenses are slightly front-focussing fully open (Noctilux, 35 Lux ASPH, 50 Lux preASPH)

- all lenses are almost spot on at 4-5.6 ( very slightly backfocussing : about 3 mm on the Leica chart)

- problem I do a lot of portrait, and I have now the focus on a strand of hair or on the eyebrows rather than the eyes…

- I don't know if any tweaking the cam will do

- I'm in the US next month and was thinking of sending everything (M8 + 3 lenses) to DAG.

- A question there : if I send it through Fedex from Europe to the US, then pick it up from DAG, will Fedex charge me some import tax in the US ?

 

 

You're nearly there, I think.

 

First, take the Nocti out of the mix. Next, concentrate on the 50 lux and 35 lux wide open. They should not be front focussing, but the point of focus at close range wide open should be in the front of the field.

 

When mine is adjusted like that, all my lenses focus all the time properly EXCEPT the Nocti, which at around f2 backfocuses very slightly (we're talking mm, not meters).

 

I suppose I could get an adjustment from DAG on that to tweak the nocti so it was "always within the focal field" too, but since I mostly shoot it wide open or occasionally pretty much stopped down to 3,2 or 4, where it's on again, I don't feel the need to do this.

 

So I think trying to calibrate with the Nocti in the mix is throwing you off.

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[wlaidlaw]

It's really becoming a rubik's cube.

I tweaked the backfocussing (main offender was my 35 summilux ASPH).

Now the situation is :

- all lenses are slightly front-focussing fully open (Noctilux, 35 Lux ASPH, 50 Lux preASPH)

- all lenses are almost spot on at 4-5.6 ( very slightly backfocussing : about 3 mm on the Leica chart)

- problem I do a lot of portrait, and I have now the focus on a strand of hair or on the eyebrows rather than the eyes…

- I don't know if any tweaking the cam will do

- I'm in the US next month and was thinking of sending everything (M8 + 3 lenses) to DAG.

- A question there : if I send it through Fedex from Europe to the US, then pick it up from DAG, will Fedex charge me some import tax in the US ?

 

There are various forms you can fill in but if Fedex get it into their heads that you owe tax, they will set the debt collectors on you to get it and totally ignore any protestations that you don't owe any tax. A wholly tax free alternative would be to send your M8 and lenses to Malcolm Taylor in the UK. He is excellent and has all the kit (optical benches etc) but you need to pin him down on timescales. Leica UK use him themselves for lens restorations. PM me if you want contact details.

 

Wilson

[JHAG]

@Jamie : thx a lot. You're right : I was strongly backfocussing (when focussiong on the "7" of a ruler, I was spot on the "8", and even the "8 1/2" (thanks to Fellini). Now, I over-corrected.

I'll try your method. In fact, all my portraits fully open are slightly off (focus on the eye gives focus on the brow). Problem is I (like all of us, I guess) shot a lot fully open. So for now I double everything with my M7.

@William : I always cringe with UK prices… I have an alternative : send camera and lenses through Fedex Express 24 to Dan when I'm in LA. I'll be there for 9 days, so it's still manageable.

[badpets]

i have backfocus issue with noctilux 50mm & 35mm sumicron asph, but 75mm apo-sumicron asph works perfectly. does that mean that my 75mm will have frontfocus issue if i do the adjustment?

[JHAG]

i have backfocus issue with noctilux 50mm & 35mm sumicron asph, but 75mm apo-sumicron asph works perfectly. does that mean that my 75mm will have frontfocus issue if i do the adjustment?

 

That's exactly part of my crucible…

[Jamie Roberts]

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i have backfocus issue with noctilux 50mm & 35mm sumicron asph, but 75mm apo-sumicron asph works perfectly. does that mean that my 75mm will have frontfocus issue if i do the adjustment?

 

Something is off then, probably your 75.

 

Without knowing which lens is newest or in best shape, I'd have to say your 35 cron--like the 28--should be bang on easy to focus with no shift stopping down. If your 75mm then needs adjustment, that's what I'd be sending in. It also sounds like your Nocti will then focus wide open properly (though it may always be off at f2-ish by a bit).

[fotografr]

- I'm in the US next month and was thinking of sending everything (M8 + 3 lenses) to DAG.

- A question there : if I send it through Fedex from Europe to the US, then pick it up from DAG, will Fedex charge me some import tax in the US ?

 

There is no tax, since you are just getting items repaired--not importing them for sale. One word of caution: When filling out your FedEx paperwork, list the M8 as a "35mm camera," rather than "Digital Camera." Electronic equipment sent by individuals (as opposed to corporations) can get held up for considerable periods going through customs, and a digital camera would fall into that category. It would be sad if the camera/lenses were being held hostage the whole time you were here.

[gravastar]

I expect you do this anyway when traveling but don't forget to take your receipts for all items so that if there are problems you can show that it's an import - export.

 

Bob.

[badpets]

Something is off then, probably your 75.

 

Without knowing which lens is newest or in best shape, I'd have to say your 35 cron--like the 28--should be bang on easy to focus with no shift stopping down. If your 75mm then needs adjustment, that's what I'd be sending in. It also sounds like your Nocti will then focus wide open properly (though it may always be off at f2-ish by a bit).

 

thank you, jamie for your input.

 

i bought all three within the last 9 months and all of them are in very good shape. never dropped or hit them.

 

35 is quite a sharp lens so even if it focus shifts, you wont be able to tell much. but i did a test yesterday by deliberately off-focus a bit in the viewfinder and the result shows a much sharper focused object.

 

i'm still thinking to adjust because i use noctilux and 35mm the most. but then i'm so scared to tweak the roller cam myself. is it really safe as some mentioned here? how can you tell if the cam is in its default position? and most importantly, what's the rate of possibly damages the M8 by doing it?

[wlaidlaw]

thank you, jamie for your input.

 

i bought all three within the last 9 months and all of them are in very good shape. never dropped or hit them.

 

35 is quite a sharp lens so even if it focus shifts, you wont be able to tell much. but i did a test yesterday by deliberately off-focus a bit in the viewfinder and the result shows a much sharper focused object.

 

i'm still thinking to adjust because i use noctilux and 35mm the most. but then i'm so scared to tweak the roller cam myself. is it really safe as some mentioned here? how can you tell if the cam is in its default position? and most importantly, what's the rate of possibly damages the M8 by doing it?

 

I think before you start tweaking the RF roller cam, you need to be sure that you have a lens or a group of lenses that is correct. Otherwise you will find you just make some lenses better and some worse. I would suggest that you go, if possible to your nearest Leica dealer taking your body and all your lenses.

 

Now Leica dealers are usually pretty helpful people, who remember they are selling premium (over?) priced products, where a high degree of customer satisfaction is required. Ask to try your lenses on at least one and preferably two other bodies. Ask to try a new lens (a 90 Summicron would be perfect) on your body. You can then begin to work out which lenses are out of adjustment and whether your body needs adjustment. It is a labour intensive and mind bending process.

 

In my case, I had access to a friend with an M8. I found that my M8 needed a tiny bit of roller can adjustment. It really is very easy - use a 2mm hex key - if you are gentle, there is virtually no chance of damaging the camera, when you adjust for perfect image coincidence at infinity. As others have said, putting the camera on a solid tripod makes the whole process easier. A lens with a long focus throw, like a Noctilux, also makes the adjustment more accurate. I recommend doing it on a clear night and either use the edge of the moon, or even better the planet Jupiter or Venus as your infinite object. A VF magnifier helps the accuracy as well.

 

On my lenses testing them over the past year or so, as I have bought, sold, swapped and exchanged to get the lens mix I really like, the WATE, 21 Biogon, 35 Biogon, 35 Summilux, 50 Summilux, 50 Summicron, 50 Elmar, 75 Summarit (2nd one), 90 Elmarit and 135 Tele-Elmar were correct. My 35 Voigtlander Nokton 1.2 was a little bit out and finally my 50 Noctilux when it came back from coding/service was a long way out, as was the first new 75 Summarit I bought.

 

Hope this helps.

 

Wilson

[badpets]

thank you very much wlailaw for your advice. but frankly, it's hard for me to trust leica repair service now since i had sent my M8 for repair for 3 months and it came back with nothing fixed at all. i think one must be really lucky to meet a dealer who knows this cameras and lense well. otherwise, they could make the issues more complicated with wrong suggestions. i dont know. so confused and frustrated.

 

I think before you start tweaking the RF roller cam, you need to be sure that you have a lens or a group of lenses that is correct. Otherwise you will find you just make some lenses better and some worse. I would suggest that you go, if possible to your nearest Leica dealer taking your body and all your lenses.

 

Now Leica dealers are usually pretty helpful people, who remember they are selling premium (over?) priced products, where a high degree of customer satisfaction is required. Ask to try your lenses on at least one and preferably two other bodies. Ask to try a new lens (a 90 Summicron would be perfect) on your body. You can then begin to work out which lenses are out of adjustment and whether your body needs adjustment. It is a labour intensive and mind bending process.

 

In my case, I had access to a friend with an M8. I found that my M8 needed a tiny bit of roller can adjustment. It really is very easy - use a 2mm hex key - if you are gentle, there is virtually no chance of damaging the camera, when you adjust for perfect image coincidence at infinity. As others have said, putting the camera on a solid tripod makes the whole process easier. A lens with a long focus throw, like a Noctilux, also makes the adjustment more accurate. I recommend doing it on a clear night and either use the edge of the moon, or even better the planet Jupiter or Venus as your infinite object. A VF magnifier helps the accuracy as well.

 

On my lenses testing them over the past year or so, as I have bought, sold, swapped and exchanged to get the lens mix I really like, the WATE, 21 Biogon, 35 Biogon, 35 Summilux, 50 Summilux, 50 Summicron, 50 Elmar, 75 Summarit (2nd one), 90 Elmarit and 135 Tele-Elmar were correct. My 35 Voigtlander Nokton 1.2 was a little bit out and finally my 50 Noctilux when it came back from coding/service was a long way out, as was the first new 75 Summarit I bought.

 

Hope this helps.

 

Wilson

[wlaidlaw]

thank you very much wlailaw for your advice. but frankly, it's hard for me to trust leica repair service now since i had sent my M8 for repair for 3 months and it came back with nothing fixed at all. i think one must be really lucky to meet a dealer who knows this cameras and lense well. otherwise, they could make the issues more complicated with wrong suggestions. i dont know. so confused and frustrated.

 

Badpets,

 

I am suggesting this much more as a "do it yourself" rather than get the Dealer to do it. All you need is his cooperation to let you try another body or bodies and lenses from his stock. This will enable to start sorting out which of your lenses, if any need their static back/front focus (often simplistically called bayonet shimming, although this is rarely the adjustment required) adjusting. Then when you know a lens or lenses are correct, you can then adjust the infinity cam on your M8 yourself. It now takes me a maximum of 5 minutes to do this but the first time you do it, it may take you somewhat longer.

 

Wilson

[badpets]

I got you, Wilson. Thank you again. I think I will follow your advice.

 

 

 

Badpets,

 

I am suggesting this much more as a "do it yourself" rather than get the Dealer to do it. All you need is his cooperation to let you try another body or bodies and lenses from his stock. This will enable to start sorting out which of your lenses, if any need their static back/front focus (often simplistically called bayonet shimming, although this is rarely the adjustment required) adjusting. Then when you know a lens or lenses are correct, you can then adjust the infinity cam on your M8 yourself. It now takes me a maximum of 5 minutes to do this but the first time you do it, it may take you somewhat longer.

 

Wilson

[Guest Ridder Cornelius]

Back Focus ?

 

One thread about back focus and all of a sudden everyone has back focus, every lens camera combination has back focus problems and has had so ever since camera-lens combinations were invented. If nobody would mention backfocus most of you wouldn't even notice a back-focus problem if it hit you in the face.... My current D3 with top notch lenses has backfocus problems, do I care? no I don't, I will only find out when I shoot newspapers and such, and I certainly don't plan on doing that. Blogs and forums are good reading, but never take it to seriously, want to find a problem.... you will find one, perhaps more as long as it doesn't disturb you whats the point?

Go out and shoot your best shot yet, back focussed and purple streaked...... perfection is boring!

[wlaidlaw]

Ridder,

 

I am going to 100% disagree with you here. I think I would and did notice the problem when my Noctilux came back from its Solms service with the focus 2 meters out at 8 meters. The very first photo I took with my new Summarit 75, I thought "that's not very sharp" and on testing it with charts, found it was about 5% out at 2 meters.

 

I print lots of my M8 shots to A3+ (48.3cm x 32.9cm) and occasionally to 100cm by 66cm. It is essential for these size prints, that focus is every bit as good as you can get it. Therefore a lens that has full aperture back-focus that is outside or even close to outside the calculated DOF, using a circle of confidence of around 0.015mm, is unacceptable to me and needs to be corrected.

 

If there is any full aperture back focus, this will only get worse with aperture shift and quite a few 35 Summilux or Noctilux lenses, can pull the focus point outside of the DOF as you stop down, producing an unacceptably out of focus picture. I like those lenses I have, which do aperture shift, set up with a tiny bit of full aperture front focus, which then unwinds as you stop down.

 

100% correct focus may not be so important to you but it is to me and many other forum members, so that is why we are very fussy about our lenses. After all, what is the point of spending up to £3,000 on a lens and then use it when it is not in perfect adjustment.

 

Wilson

[badpets]

Wilson,

I adjusted M8 already using Noctilux and focus became so much better now with all my lens, including my 75mm which I thought would probably have frontfocus after adjustment. I feel so much relieved/comfortable with my M8 now. Thanks for you advice!

 

Ridder,

Backfocus issue doesnt bother you, but our seeking for better focus bother you? Why?

 

Ridder,

 

I am going to 100% disagree with you here. I think I would and did notice the problem when my Noctilux came back from its Solms service with the focus 2 meters out at 8 meters. The very first photo I took with my new Summarit 75, I thought "that's not very sharp" and on testing it with charts, found it was about 5% out at 2 meters.

 

I print lots of my M8 shots to A3+ (48.3cm x 32.9cm) and occasionally to 100cm by 66cm. It is essential for these size prints, that focus is every bit as good as you can get it. Therefore a lens that has full aperture back-focus that is outside or even close to outside the calculated DOF, using a circle of confidence of around 0.015mm, is unacceptable to me and needs to be corrected.

 

If there is any full aperture back focus, this will only get worse with aperture shift and quite a few 35 Summilux or Noctilux lenses, can pull the focus point outside of the DOF as you stop down, producing an unacceptably out of focus picture. I like those lenses I have, which do aperture shift, set up with a tiny bit of full aperture front focus, which then unwinds as you stop down.

 

100% correct focus may not be so important to you but it is to me and many other forum members, so that is why we are very fussy about our lenses. After all, what is the point of spending up to £3,000 on a lens and then use it when it is not in perfect adjustment.

 

Wilson

[pklein]

One of the problems with pinning this down is that there are always four factors involved:

 

- How good is the photographer's focusing ability?

- Is the camera calibrated to M8 tolerances?

- Is the lens calibrated to M8 tolerances?

- How much does the lens focus shift?

 

It is always possible to blame the photographer, but this does not disprove the problem. Ditto the lens and the camera adjustment. If the lens focuses correctly wide open, but not when you close down, then you've got focus shift.

 

Here are two photos at 100% pixels (1:1) with my 35/1.4 Summilux ASPH. The focus is on the paper clip where it intersects the yardstick at the 28-inch mark. The first picture is at f/1.4, the second at f/4.0. You can see that the focus is pretty much dead-on wide open and shifts back when the lens is closed down. I have done this kind of test numerous times, and gotten the same result most of the time.

 

Fortunately, we don't normally print or view real photographs at 1:1. At 50% (1:2), the 28-inch mark appears to be just inside the zone of acceptable focus at f/4.0. This is about what an 8x10 print would show. So, for real photographs at f/2.8 - f/5.6, I focus on the closest thing I want in focus, and I'm usually OK. And if there's no time to do that, I just focus, shoot, and I'm still usually OK.

 

Now if I printed 16x20 prints that viewers would "smell" while viewing, I might have a different opinion.

 

And focus shift is not limited to the ultra-fast lenses. I can detect it on all my lenses of f/2 and faster.

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[JHAG]

@pklein : this is just my problem.

I adjusted my M8 for a heavy backfocus (mostly on my 35 ASPH),

and now my 3 main lenses (35, 50 and Noctilux) frontfocus a bit

when fully open, and are spot on around 4/5.6.

Pretty annoying because I just bought a large format printer.

So back to the cam and fine-tuning again, with the help of some

here.

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[JHAG]

Sorry if I'm back with it again.

Having tested and re-tested, both 35 and 50 are on focus now.

Noctilux is slightly front-focussing fully open and slightly back-focussing

at 2.8

But my elmarit 90 is not : fully open, it's front-focussing a lot,

and slightly back-focussing at 5.6.

All lenses are nexw or less than 4 years old.