Accuracy of M8's rangefinder system

[jaapv]

Originally Posted by lxlim

yes. about 2-3000 times in the last 6 weeks. It was a tripod job. By moving my eyes further away from the viewfinder the focusing patch fills the viewfinder making it easier to nail my focus exactly. Same as using the magnifier at waist level on a Twin lens reflex or a reversed loupe from the back of a 4x5 with groundglass removed. Basically a spot magnification of the point of critical focus. Not with a magnifier so far as I have not purchased it yet. I will give it a try with the magnifier.

With the viewfinder, I have 90% keepers at f2.8 1/30 at ISO640. with the MegaPerls 1.35X, I have 40% keepers. With the 1.25X (tested in the shop) I got 0%

I might be fitting it wrongly but so far I was unable to find out where it could go wrong. None of the sales guys could tell me where I am going wrong in fitting it, they could not focus on it either.

Actually it is three guys and three magnifiers who are unable to focus with it and one guy who could focus accurately did not have fully corrected vision which makes me inclined towards shootist's explanation that the M8's rangefinder having a -0.5 diopter correction built-in. That guy could not focus with the viewfinder alone accurately. That would account for me seeing a slightly out of focus viewfinder.

Thanks.

It is not the sharpness of your eyes,which is the thing that your optometrist tests, it is a thing called vernier acuity that is at the basis of RF focussing. (Not that that is wholly dissociated from sharpness and astigmatism.)If that is off a little the error may be magnified - by the magnifier And yes, the magnifier changes the strength of the viewfinder ocular by 0.5 dioptre. It could just "push you over the edge of unsharpness"
In other words: it aint that simple....

[lxlim]

Originally Posted by jaapv

It is not the sharpness of your eyes,which is the thing that your optometrist tests, it is a thing called vernier acuity that is at the basis of RF focussing. (Not that that is wholly dissociated from sharpness and astigmatism.)If that is off a little the error may be magnified - by the magnifier And yes, the magnifier changes the strength of the viewfinder ocular by 0.5 dioptre. It could just "push you over the edge of unsharpness"
In other words: it aint that simple....

Yikes! What should I do about that, Jaap?

BTW can Leica modify the M8 with a higher magnification finder? I may have to dedicate one M8 for the 50mm to 90mm range. How high a magnification can I go? And will such a viewfinder reproduce the same problem with the 1.25X magnifier?

Thanks, Jaap. Much appreciate your thoughts on this. Vernier Acuity, not something I learn about in photography forums usually......

[diogenis]

But Jaapv, he said that upto and using his camera without a magnifier, everything is fine. His problems begin when he installs those addon magnifiers.
However, this gave me an idea Alex: next time you visit your optician, take the camera with you and show him the problem. I'm sure he will be able to help

[markgay]

Re vernier acuity:

That's why I said, "A large, bright split image snaps into focus. You don’t have to STARE at it. You know when it’s in focus. Something like instinct."

Human eyes are very good at it - much better at identifying a split line than any other focus mechanism.

http://www.pc.ibm.com/ww/healthycomp...vdt13eyee.html

"Vernier acuity is the ability to detect a discontinuity in a line or the misalignment of a segment of a line. This ability is about 10 times greater than minimum separable acuity."

Hence the superiority of the split image rangefinder, at least up to 90mm focal length. It's not to do with the length of the lens but the abilities of the eye.

The fact that digital sensors have tighter tolerances than film is a phenomenon that affects all focusing systems.

I explained the disadvantages of autofocus for me but that's really a separate matter.

[dalippe]

Originally Posted by lxlim

Likewise. The rangefinder patch is quite beautiful in use. Far better than an DSLR in the sort of work I deploy it in.

What I love about it is this. I can focus, get my shot, tilt the camera over to check the lcd image to see if I got the shot, make slight adjustment if necessary to the focus without looking through the viewfinder, reframe and shoot it and bang on, it is sharp. The lens precision assembly does not shift or wobble like those of AF lenses and delivers consistent results.

The only problem I have with my M8 really is that I do miss some of the amenities of the modern DSLRs. but I will make do with what I have and work a little harder.

Different application indeed than what has come to dominate my photography in the last 15 months! My son and M8 arrived around the same time. Needless to say that the thrill my son takes in running around completely precludes any second tries at focus. On tight crops, I definitely get more in-focus shots from my DSLR, but that doesn't stop me, wisely or not, from using my M8 95% of the time. And presumably my manual focus speed is improving faster than it would in the absence of this challenging subject....

[jaapv]

Originally Posted by lxlim

Yikes! What should I do about that, Jaap?

BTW can Leica modify the M8 with a higher magnification finder? I may have to dedicate one M8 for the 50mm to 90mm range. How high a magnification can I go? And will such a viewfinder reproduce the same problem with the 1.25X magnifier?

Thanks, Jaap. Much appreciate your thoughts on this. Vernier Acuity, not something I learn about in photography forums usually......

I went to my optician and held correction lenses between the camera and my eye until I knew the exact correction. +1.0 without magnifier, + 0.5 with magnifier. Then I got the Megaperls 1.25, found it wobbly, now I use the Megaperls 1.15 and am totally happy.

[lxlim]

Originally Posted by diogenis

But Jaapv, he said that upto and using his camera without a magnifier, everything is fine. His problems begin when he installs those addon magnifiers.
However, this gave me an idea Alex: next time you visit your optician, take the camera with you and show him the problem. I'm sure he will be able to help

The solution may well be a customised diopter adjustment. I hope not because an optician friend of my said it cannot be done in my country and needs to be done in UK or the US.

[lxlim]

Originally Posted by jaapv

I went to my optician and held correction lenses between the camera and my eye until I knew the exact correction. +1.0 without magnifier, + 0.5 with magnifier. Then I got the Megaperls 1.25, found it wobbly, now I use the Megaperls 1.15 and am totally happy.

Now lets see. -0.5 (rangefinder built-in correction) + 1.0 (Jaap eye correction, no disrepect meant ) = 0.5 diopter correction.

In my case -0.5 (rangefinder built-in correction) + 0 (My eye correction) = - 0.5 diopter correction

I think I got my math right here. I believe i am going to be a happy camper too.

Your Megaperls 1.25 got the wobbles too, eh? I regretted the decision to get two of them sight unseen. Does the Megaperls 1.15 have the diopter adjustment?

Much thanks Jaap, you are a treasure. Diogenis, you too

[jaapv]

No- it is most stable and imo a far better product. The dioptre adjustment is stiffer as well. The field of view works for 28 mm and I suspect even 24 mm whilst it still enhances accuracy.

[lxlim]

Originally Posted by jaapv

No- it is most stable and imo a far better product. The dioptre adjustment is stiffer as well. The field of view works for 28 mm and I suspect even 24 mm whilst it still enhances accuracy.

Thanks. I will probably get it.

[Jamie Roberts]

Originally Posted by jaapv

It is not the sharpness of your eyes,which is the thing that your optometrist tests, it is a thing called vernier acuity that is at the basis of RF focussing. (Not that that is wholly dissociated from sharpness and astigmatism.)If that is off a little the error may be magnified - by the magnifier And yes, the magnifier changes the strength of the viewfinder ocular by 0.5 dioptre. It could just "push you over the edge of unsharpness"
In other words: it aint that simple....

Ahh--no wonder I love the magnifier with the M8. My optometrist said I need the very smallest bit of + diopter for my eyes

When the M8's RF is aligned, I find the RF mechanism superior to any AF I've used to date, including moving subjects. When I'm really tired, though, the AF comes out (except in low light--the M8 is still better).

On the DMR, it's been a real struggle for me to get good focus without stopping down a lot.

The Brightscreen screen and magnifier were, in a word, terrible. The basic DMR screen not any better; I bought a new screen from Leica on Rob S.'s recommendation and it's much better, though I wish there was a magnifier as good as the DMR as for the M8.

I'm currently getting all my R lenses checked (right now the best is the 100 APO macro), and since I have a ton of shooting to do in the next months, I'm hoping I get this solved, since I'm ever more in love with the DMR files (and love using the M8 and DMR together, because they look so similar when processed

[jaapv]

The only thing that works for me on the DMR ,I tried the standard screen and the microprism screen as well, is the full matte screen. I learned to love that on the Visoflex.

[adan]

Coming to this thread a bit late - this is the conclusion I've reached, within the past week, after a winter (and in reality the whole 18 months I've had M8's and the whole 7 years I've had Leica Ms) of playing around with various long and medium lenses:

The magic of an RF comes when one can simply, as MarkGay and noah_addis have said, "snap" the two images together once and have a very high - and comfortable - confidence of a focused image at maximum aperture - without having to rack the lens back and forth, back and forth (which is, as Magnum's Dave Harvey put it, a technique for SLRs).

That limit for me is "70-75mm" equivalent @ f/2, at least on those Ms that include the 28/35 field of view (M8 and .72x film Ms). A 75 'cron for full-frame, and a 50 'cron on the M8.

That does not mean that longer lenses cannot eventually be focused. Just that for fast journalistic, documentary reportage, I've put aside the 50 f/1.4 and the 75s and 90s.

Fortunately, a "70-75" f/2 is JUST long enough and fast enough to be a detail lens and a portrait lens and a subject-isolating lens - IF one can get close enough. Which is always the photojournalist's goal (Remember Capa's dictum).

(Part of this past winter was spent playing around with some medium-format film gear, and I was interested to note that a 50mm on the M8 is about exactly equal in framing to a 150 on 120 film, assuming one crops the M8 image to 6x7 or 6x6 shape. And of course 150mm is the upper limit for the Mamiya 6/7 rangefinders, as well as being the most common long lens for many Hassy users.)

So I've come to terms with the fact that just because Leica makes longer lenses does not mean I have to use them, if they are outside my comfort zone. My 15/21/28/50 prime shooting set is very similar to a Mamiya 7 user's 43/65/80/150.

Historically, very few Leica users of note have strayed much beyond 50mm FOV - especially once SLRs became an option. In no particular order - Paul Fusco (21/28/35 on an M and a 180 on an SLR); Jill Freedman (21/35 on an M and 105/180 on a Nikon); Harvey/Meiselas/Webb/Franklin/Salgado at Magnum (28/35/50 most of the time); David Douglas Duncan (28 and 50 on M3's + a 200 on a Nikon for his Vietnam work).

If I really need a 75/85 f/1.4 or anything longer - I'll find an SLR. Thus far I have been able to avoid the temptation through just moving closer.

I started out with a Canon FX SLR that had a split-image prism in the finder. And I've been addicted to split-image ever since (part of what drove me to RFs was the evaporation of split screens in most modern SLRs). My own perception is that the accuracy curves for SLR (split) vs. rangefinder (40+mm effective base) cross over somewhere between 50mm and 85mm (on a full-35mm-frame camera). Aperture plays a role, though. An 85mm f/4.5 setting on an SLR zoom is much harder to focus than an 85 f/1.4 (SLR) or 75 f/1.4 (RF) because the "baselength" of an SLR split-image is essentially the wide-open aperture of the lens.

[delander]

Originally Posted by lxlim

I would appreciate your testing as my dealers do not have a set of diopters to check this out.

Thanks, hopefully that is the answer.

Alex

Just an update on this. Yesterday I visited Richard Caplan in London since I know that they keep a virtually full range of Leica correction lenses. I tried several, using them with my 1.25 Leica magnifier which previously had given me larger but less clear images, so I had in fact abandoned it.

I tried three, +0.5. +1.0 and +1.5, focussing on items in a display cabinet some 2 metres away and then on a very useful set of iron railings across the road. I took my time over this in order to try to get it right.When I got to the +1.5 it was clear that for me the +1.0 correction was the best.

I confirmed this result this morning. I focus on a small grid of 16 squares just 13mm sq
(blank finely bordered cells, printed on white paper, from MS Excel) from a distance of 1.7 metres. The cells now snap absolutely clearly into focus.

A great result.

Jeff

[Shootist]

And I suspect you use NO diopter at all without the magnifier.
Younger eyes can make the changes needed when going from standard viewfinder to one with a magnifier attached. Older eyes, like mine, can no longer make those changes, IE that is why we older folks wear reading glasses and need a different diopter when using the magnifier.

Originally Posted by delander

Just an update on this. Yesterday I visited Richard Caplan in London since I know that they keep a virtually full range of Leica correction lenses. I tried several, using them with my 1.25 Leica magnifier which previously had given me larger but less clear images, so I had in fact abandoned it.

I tried three, +0.5. +1.0 and +1.5, focussing on items in a display cabinet some 2 metres away and then on a very useful set of iron railings across the road. I took my time over this in order to try to get it right.When I got to the +1.5 it was clear that for me the +1.0 correction was the best.

I confirmed this result this morning. I focus on a small grid of 16 squares just 13mm sq
(blank finely bordered cells, printed on white paper, from MS Excel) from a distance of 1.7 metres. The cells now snap absolutely clearly into focus.

A great result.

Jeff

[delander]

You are right Ed, it is only with the magnifier that I have found the correction lens to be an improvement.

Jeff

[diogenis]

Guys, diopters correct for what, Myopia or astigmatism?
I never had to wear any glasses, as my eyesight is perfect. And a small myopia of around .75 when I was younger seems to auto correct now that I am older (must be .90-.95 now). However I noticed that playing with diopters on my binoculars, nothing happened. Maybe it's astigmatism they correct?

Edit: I just made a mistake: myopia I meant on my right eye. My left one was always bionic 10/10

[jaapv]

Myopia. (front or backfocussing eyes )It is possible to correct for astigmatism using an empty holder (supplied by Leica) and a lens made by an optician, but that has some complications. Firstly there are not many opticians that will supply a 10 mm lens. Secondly, if you correct for astigmatism it will only work when you hold the camera horizontal. As soon as you swing it 90 degrees, it corrects just the wrong way aggravating the problem. So for portrait you have to focus-and-turn

[lxlim]

Originally Posted by delander

Just an update on this. Yesterday I visited Richard Caplan in London since I know that they keep a virtually full range of Leica correction lenses. I tried several, using them with my 1.25 Leica magnifier which previously had given me larger but less clear images, so I had in fact abandoned it.

I tried three, +0.5. +1.0 and +1.5, focussing on items in a display cabinet some 2 metres away and then on a very useful set of iron railings across the road. I took my time over this in order to try to get it right.When I got to the +1.5 it was clear that for me the +1.0 correction was the best.

I confirmed this result this morning. I focus on a small grid of 16 squares just 13mm sq
(blank finely bordered cells, printed on white paper, from MS Excel) from a distance of 1.7 metres. The cells now snap absolutely clearly into focus.

A great result.

Jeff

Thanks Jeff.

My problem is that my dealer do not have a set of correction lenses here in Singapore nor do the agents.

I might go for the Megaperls 1.15X as recommended by Jaap except that I would like a little more magnification.

Alex