M8 backfocus test - please comment

The images below are a series of test shots to check for back-focus on my M8. I have owned the camera about 5 weeks and had ongoing focus issue, so added the 1.25x magnifier but still had issues. An answering post on another thread suggested this test to see if the camera rangefinder needs adjusting. After looking at the results I think it definitely needs it unless I care to shoot at f11 or f16 exclusively. Camera is on a tripod with cable release. Yardstick is secured to the table top, camera is at 45 deg angle to the yardstick. My focus point is at the 20 inch mark, and I included cards showing the aperture for each exposure. Of course no sharpening or other PP, and the lens is a new coded 355 summicron.

I start with the f11 shot (won't include the f16, it looks even better, greater DOF and also am skipping the f8 shot so I don't take too much of your time). It seems pretty evident to me as the aperture increases that the focus point is in fact not at the 20 inch point that I focused on but somewhere further out, say around the 18 or even the 17 inch mark.

Questions to you all:
1. Do you see the same thing?
2. Do you see any errors in the way I've tested?
3. Is the term "back-focus" or "front-focus" the correct one?

Thanks for your time!











--
-Steve
'Living is not enough -- we have to talk about it' -(Samuel Beckett)

clearly the problem is there. now, does it happen with all lenses, or just with this one? if it happens with all lenses, rangefinder on your m* needs to be adjusted. if it is just your 2/35, blame the lens.
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Irakly Shanidze
http://www.shanidze.com/en

I only own the 1 lens! So, I'm thinking that maybe I should just ring up Leica USA in New Jersey and set up a return of the M8 for adjustment, check it out after return, then follow with the lens if required. Short of finding someone to lend me another lens, that is...
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-Steve

Yep! That's back focus all right. Sorry to see this. I agree that the critical plane of focus is at about the 17" mark.

How old is you lens? A lens focusing cam is a pretty simple construct and really very little room for error. They can, however, become worn with age. But this focusing error seems pretty drastic - more than I expected in our previous communications. I once tested a summilux at f1.4 and was concerned about a difference of about 1/4".

Personally, I'd see if sending out both the lens and the camera is an option and say, "make it happen". Otherwise, there's the potential for taking twice as long and twice the cost and still have a camera and lens focusing cam that doesn't agree. Of course then Leica (regardless what it takes to fix) will probably automatically say it's not the camera (which is under warranty) but that it's the lens (which is not), and charge you. But at least you will have a camera/lens combo that is dead on.

I don't see you mention which lens you are using?

There is an interesting thread on the Leica digital forum discussing this same topic. That poster sent his 35mm Summilux-M into Leica also complaining of backfocus issues. Leica's response to him is that's normal--to a limited degree.

http://www.leica-camera-user.com/digital-forum/17699-very-interesting-answer-leica-35mm-1-a.html

Not surprising on the 35mm f/1.4 Leica designs the lens to have the most accurate focus wide-open. As the lens gets stopped down it progressively begins to have more back-focus. Apparently this is a property of lens design that can be controlled and limited but only in combination with other factors. As you make the back focus better some other aberrations may get worse.

Whether your lens is back-focusing more than normal or if your camera rangefinder needs adjustment only a trip to the service center will tell. It's sad though waiting for it get returned. Leica seems pretty backed up these days.

What you are seeing is almost certainly a characteristic of that lens, not a fault as such, and not with the camera.

There is an extremely exhaustive thread on the LUF that I started and have pursued relentlessly. It is 11 pages long and growing and I am slowly proving my point, which is (and as you will read, this has been confirmed by Solms) that the 35 lux and cron both exhibit backfocus such that as you stop down between particularly 2.8 and 5.6, the point at which you have focussed AT THE CENTRE OF THE FRAME ONLY will go OOF as focus shifts backwards. This results from those lenses having been designed for film. All is explained at:

http://www.leica-camera-user.com/digital-forum/17699-very-interesting-answer-leica-35mm-1-a.html

I stress that many people disagreed with me but many others found the same thing. In the end, a number of people tested their lenses more thoroughly and found that I was right. Solms, as I say, agrees.

However this does not mean that your RF alignment is perfect though it probably is.

To test your RF you need other lenses that you trust or other people trust. Try a 50 cron if you can. But a quick down and dirty test it to point the camera at the moon, see if it is perfectly aligned in the RF when the lens is set to infinity, and take a shot to confirm that it's sharp.

If your RF is out horizontally, which is the most common, then there are sections of the above mentioned thread that will show you how to adjust it yourself with a 2mm Allen key. It is easy if a little time-consuming, but it may invalidate your warranty. I don't see a way that anyone unless a total klutz could damage their camera by trying. I've done it and gained a very marginal improvement.

You will almost certainly find that your Cron's backfocus happens at the centre and not the whole frame. A good viable alternative is the CV F2.5 35mm which is sharp and very cheap.

Hope this helps

Tim

ps, if you do get into that thread, take at least an hour to read it all. The truth emerges towards the end but you have to follow the arguments!
--
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/

Tim, as usual, I thank you for taking the time to respond...

Seems as though I've spent good money in good faith on a crippled design as regards using it on the M8 - assuming that there are times I want to use f4 (like daily?). I will take the time to read the long thread, but it seems that Leica needs to start designating their 35mm lens offerings as "not recommended for M8" or something to that effect.

Does this "designed for film" issue apply to other lenses as well?
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-Steve

My initial assumption was camera needs adjustment - but see Tim's response below, that both offerings in the 35mm series exhibit this backfocus when used with the M8...

Isn't this just ducky?

Thanks for your input on how to conduct this test. You know, at least now I can feel better about my focus difficulties over the past month, that my failures are designed into the lens!
--
-Steve
'Living is not enough -- we have to talk about it' -(Samuel Beckett)

Thanks for your comments. These shots came from a new 35mm summicron, which seems to have this backfocus designed into it - not a problem on the film Leicas but a real issue on the M8. So, it seems I've dropped $2200 on a wonderful lens that must be used at f8 to f16 or maybe at f2 if your lucky!

Lordy, lordy!
--
-Steve
'Living is not enough -- we have to talk about it' -(Samuel Beckett)

Well,,

How far away is the 20" focal point from your lens?

Try your experiment at 7 ft distance and see what results you get. Rangefinders are not really that good at very close distances. I think that's supposed to be relativley common knowledge.

I recently read that the 7 ft. distance is the viewfinder focal plane that the rangefinder is set to. Meaning it won't be as accurate at a closer distance and at a further distance it would not matter.

Are your regular images out of focus? I'm talking about close up portraits, and then a little farther away general type people shots and landscapes.

You are aware that your body may sway more than 1" as you take photographs so none of your problems would be real world problems.

Mounting a Leica on a tripod is not usually done, since close focusing accuracy is inherently poor and tripodmounted landcape photography cameras are not traditionally rangefiners cameras.

The Leica is a small and fast 35mm format machine, it's not designed as a studio, macro or landscape machine. It will do all those tasks but that was not what it was designed for.

I think you should use your camera a while and get used to it's strengths and enjoy it. I'm sure you will come to realize it does work well and your images will be sharp and clear.

One last question, do you normally wear glasses? If you do perhaps you should get a vision correction diopter and mount it on the 1.25 magnifier. You will be suprised at how much more clear the coincedance images will colide into focus in the patch area.
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Artist Eyes

I've said as much to them in effect. I think this only affects these two lenses BTW.

BUT: they are still superb lenses: I'm keeping my 35 cron. Why?

Mine does a great job at F2. At F2.8 through 5.6 or 8, depending on distance to subject, it is unreliable in the centre of the the frame but you will very often not notice, because we all tend to focus then recompose with the subject on a third, which generally brings it neatly into focus. Plus at F8 and 11 the results can be fab.

Bottom line: if you get to grips with what it does and when it does it, the results are not bettered elsewhere and can be stunningly crisp and detailed in a way that other lenses at this length don't quite achieve. And it's F2 abilities make it a great low-light lens.

I've gotten used to mine. It's not ideal but with practice it's pretty damned good! Just not as an only lens. If you only want one lens, get the 50 lux. It is astonishing.

Tim
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Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/

Peter, this effect is very clearly visible at longer distances. I posted examples on the LUF where I focussed on something centre frame at F4, about twenty five feet away, with a tripod, and it was OOF but background stuff more like fifty feet away was crisp, as was edge detail at the same distance as the main subject.

Tim

Peter Nelson said:

Well,,

How far away is the 20" focal point from your lens?

Try your experiment at 7 ft distance and see what results you get.
Rangefinders are not really that good at very close distances. I
think that's supposed to be relativley common knowledge.

I recently read that the 7 ft. distance is the viewfinder focal
plane that the rangefinder is set to. Meaning it won't be as
accurate at a closer distance and at a further distance it would
not matter.

Are your regular images out of focus? I'm talking about close up
portraits, and then a little farther away general type people shots
and landscapes.

You are aware that your body may sway more than 1" as you take
photographs so none of your problems would be real world problems.

Mounting a Leica on a tripod is not usually done, since close
focusing accuracy is inherently poor and tripodmounted landcape
photography cameras are not traditionally rangefiners cameras.
The Leica is a small and fast 35mm format machine, it's not
designed as a studio, macro or landscape machine. It will do all
those tasks but that was not what it was designed for.
I think you should use your camera a while and get used to it's
strengths and enjoy it. I'm sure you will come to realize it does
work well and your images will be sharp and clear.
One last question, do you normally wear glasses? If you do perhaps
you should get a vision correction diopter and mount it on the 1.25
magnifier. You will be suprised at how much more clear the
coincedance images will colide into focus in the patch area.
--
Artist Eyes

Click to expand...

--
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/

Peter Nelson said:

Well,,

How far away is the 20" focal point from your lens?

Try your experiment at 7 ft distance and see what results you get.
Rangefinders are not really that good at very close distances. I
think that's supposed to be relativley common knowledge.

I recently read that the 7 ft. distance is the viewfinder focal
plane that the rangefinder is set to. Meaning it won't be as
accurate at a closer distance and at a further distance it would
not matter.

Mounting a Leica on a tripod is not usually done, since close
focusing accuracy is inherently poor and tripodmounted landcape
photography cameras are not traditionally rangefiners cameras.
The Leica is a small and fast 35mm format machine, it's not
designed as a studio, macro or landscape machine. It will do all
those tasks but that was not what it was designed for.

Artist Eyes

Click to expand...

--I would be interested to know the source of your information on the rangefinder being less accurate at its closest focusing range cus I have never seen this before and I am always wanting to learn something new. In the fifty years I have been using leicas I have never noticed any back focus problems but then I wasnt looking for them either but at least for me it has not been an issue but also I dont have an m8 yet.

Leica M camera and lenses were indeed designed to be a comprehensive camera system able to do general photography. It is an urban myth that it was designed for photo journalism though it is true that its best at this.
bosjohn aka John Shick [email protected]

Until now, I have defended the M8 and was about to sell all unrelated camera equip. to get one. The remaining IR problem has been of no concern to me at all. But if the statements about the 35mm lenses are true (and I assume it is since Leica admits), then I am finally and completely over the M8. This is totally ridiculous, ridiculous, ridiculous. It really dissapoints me that Leica hasn't made this public and is selling $2500 lenses and an M8 to Digital rangefinder newbies who don't know any better. I've been shooting 35 summilux asph 1.4 w/M6 for several years. I've similarly tested for backfocus and was concerned about a backfocus of 1/4", not 3 inches. I can't believe I have been lusting for a camera costing $5000 that completely destroys what, in my opinion, is the Leica rangefinders whole purpose. That being the ability to shoot in natural light with fast lenses that are smaller than a breadbox and rendering a quality that is unequaled. What possible reason would one have for spending $2500 + for a f1.4 or f2 lens other than to have the option to using it wide open?

Also to suggest buying a 50mm lux as a stand alone lens for the M8 is inconceivable (sorry Tashley - no offense). With the mag. factor, that's a portrait/telephoto lens. Every seasoned Leica shooter knows that the 35mm has always been the preferred "standard" lens on film which is now a 50mm on M8. A short tele lens on a Leica rangefinder (as a standalone) shuts the door on at least 75% of what makes rangefinder photography shine.

Leica - Digital M8! You've finally lost me. I can put this lustful torment away for now.

Hi John,

Well I read this last nite on the RangeFinders Forum. I don't know who posted it and it was probably a reply in someone's thread so I'll probably not be able to find it again. Just becase we never ran accross it before does not make it false. But I realize now that it does not make it true either.

If you really need to find out for sure I think Leica is the only scource to go to as they make the M cameras. Please if you do that let us know what they say, thanks.

I think Tim's response will hold true as he did contact Leica on the lens.

--
Artist Eyes

Golden Rule:

If the focus is set on a point where you want to have it, then changing in F stops should not change the focuspoint at all, if that is happen then there is a problem with the lens or camera or the combination of it.

The field of dept change with different F Stops, not the focus point.

My M8 is also back to Leica for the same back focus problem.

Theo

Hold it,

Can we have someone post a real word image from the M8 and the 35mm lens in question, and at the apertures in suspect?

Real world photos tell us more about any lens test.

Do you really believe you have the ability to hand hold and get perfectly focused images every time out in the real world of the type and tolerances capable of being done by a machine. I don't think anyone is. The machine can't do it either because it's not out there in the streets.

So it does not matter about our misconception of perfect lens focusing, not in the real world.

Please name your equipment that you are positive you can focus 100% perfectly evertime while your using it? That means a picture of someone 5-10-25 feet from you and the of point of focus is always 100% accurate for you within 1/4". You can't do it, no one can.

There is no such thing as perfect.

--
Artist Eyes

rollei53 said:

ridiculous, ridiculous, ridiculous. It really dissapoints me that
Leica hasn't made this public and is selling $2500 lenses and an M8
to Digital rangefinder newbies who don't know any better.

Click to expand...

See - you've got years of experience with the M series, but this bug would have bitten you as well! Seems like maybe Leica did not know that the flatness of the new sensor does not equal the flatness of film - but all of us are learning about it together!

If the issue only affects the 35mm lenses I can live with it, replace it with a 28mm or one of the Zeiss or CV offerings. I strongly feel, however, that Leica absolutely must attach a caveat to these lenses as regards using them on the M8 - I would still have purchased the camera, just started out with a different lens...

As always, thanks for your comments and insights. I'm also glad that you suggested these test shots in the first place - I really was pulling my hair out over my inability to properly focus a lens that cannot help itself at f4.0
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-Steve

Peter, see this thread, it is a couple of shots posted from this past weekend and is the starting point for why I needed to do this test. I agree - who cares that I can't get good sharp photos of my yardstick! My problem has been that I can't get good sharp photos of lots of things if I'm working at f2.8 up to f5.6 or so

http://forums.dpreview.com/forums/read.asp?forum=1038&message=22524415

--
-Steve
'Living is not enough -- we have to talk about it' -(Samuel Beckett)

I don't really want to be argumentative here. I'm trying to contribute helpfull questions.

But even you yourself on that thread said they were not good pictures to judge focusing. They were not all that bad considering they are action shots.

Have you had poor focus with all your pictures?

Also you never said if you wear glasses having the 1.25 magnifier as you do will not correct your vision only a diopter will do this. I use both and now my pictures are focused.

Manually focusing action shots takes some practice.

Have you concentrated carefully on your focusing point on a more static subject and made an effort to remember where it was in any other real world pictures, and then have you found the lens did not focus where you know it was focused.
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Artist Eyes