Testing rangefinder accuracy on an M240

[chaospress]

Testing focus accuracy

Conditions:

1) new Leica M240
2) 50mm Summicron set at f/2
3) camera on tripod, ISO 200
4) testing focus on subjects at varying distances

I am making 2 identical shots, one focused with rangefinder, one with pixel peaking in live view on my M240. It appears focus peaking on live view is *usually* more accurate than focusing with the rangefinder. A bit perplexing because on a couple of shots the RF focus resulted in as good or better focus than focus peaking, but not on most of them.

This has me wondering if photographer's error may be in play. Just wanting to determine if my rangefinder is off because the camera was delivered, let's say, not that well packed, though I would think the inner Leica box would protect it.

I thought a possible issue might be that I use a -1.5 diopter correction lens on the body, so I wonder if that could be inadequate, though when I focus with the RF the subject in the focus patch appears sharp. I also wear glasses when looking at live view and wonder if that could be throwing another wrench in the works.

Hmmm... ?

 

[BLKRCAT]

Check out this post, it may be of some help to you

http://www.rangefinderforum.com/forums/showthread.php?t=109748

 

[V-12]

This has me wondering if photographer's error may be in play. Just wanting to determine if my rangefinder is off because the camera was delivered, let's say, not that well packed, though I would think the inner Leica box would protect it.

Comparing the rangefinder result with the Focus Peaking result is the obvious way to check, but as with any other Leica M (style) camera the rangefinder is never going to be as perfectly accurate as focus peeking simply because it can't compensate for 'focus and compose' situations (unless the composition is dead centre in the middle of the frame each time). So to some extent the user has to anticipate when a bit more DOF is useful, when to push or pull focus to compensate for re-composition, etc. As such it is only real world use that can dictate the useful accuracy of the rangefinder because the photographer still needs to input some skill and planning, it isn't a perfect art even with a perfect rangefinder. So I'd suggest you use the camera and only when you feel you've got the hang of it worry if you constantly get OOF images.

V

 

[jaapv]

As long as you are not using a tripod the movement of your body will invalidate this type of test.

 

[willie_901]

Mechanical focusing accuracy depends on more variables than live view.

Critical focus at wide apertures and relatively short subject distances is not a strength of optical rangefinders. And in these circumstances camera motion and unintended body movement is relevant as it is for many AF modes as well.

I think it's great to have a camera one can use on a tripod with live view for critical focus or with a mechanical RF at narrower apertures for more spontaneous work.

 

[chaospress]

V-12, the test was with focus on subject dead center and without camera movement after focus. I've been using Leica rangefinders for quite a long time so there's no issue with getting the hang of it. Your post is helpful nonetheless, thanks.

jaapy, test was on a tripod.

Willie, I wondered if that might the case with close distances, thanks.

 

[photomoof]

Just out of general curiosity, it is possible to take good photos while looking at focus peaking?

Seems an awful way to work to me. But just me, of course.

 

[Mackinaw]

Just out of general curiosity, it is possible to take good photos while looking at focus peaking?

Seems an awful way to work to me. But just me, of course.

A friend has lent me her M-240 for the past few months.

I don’t use focus-peaking with any of my M-mount optics, but it has come in quite handy with some of my old Canon FD telephotos, specifically the FL-F 500mm Fluorite lens (of course, on a tripod).

Jim B.

 

[chaospress]

Just out of general curiosity, it is possible to take good photos while looking at focus peaking?

Seems an awful way to work to me. But just me, of course.

Yes, since for the past couple of years I've been working with urban landscape/ still objects, with the M240 I've been using the screen with Live View more often than not, taking time and carefully composing. You first focus peak with magnification, then tap the shutter button to go back to the full scene, and shoot.

The camera gives you the option of working that way or shooting the same way you would with a film M, M8 or M9.

 

[jaapv]

Do note that it makes a difference whether you focus coming from infinity or from close up due to gear lash. For consistency make it a habit to return the lens to infinity.

 

[chaospress]

Do note that it makes a difference whether you focus coming from infinity or from close up due to gear lash. For consistency make it a habit to return the lens to infinity.

Have to admit in 12+ years of internet discussion on Leicas I've never seen this mentioned.

 

[Range-rover]

Great thread I'm glad someone started it.

Range

 

[photomoof]

Do note that it makes a difference whether you focus coming from infinity or from close up due to gear lash. For consistency make it a habit to return the lens to infinity.

Really? You feel that the cam and lens helical is that sloppy on a Leica?

Not that I doubt it, but I cannot imagine starting focus from infinity between shots.

 

[willie_901]

...
Willie, I wondered if that might the case with close distances, thanks.

It's just that at close distances with f2 the DOF is narrow. The narrow DOF mean any inaccuracy in the optical/mechanical RF becomes more important.

By contrast any RF inaccuracies are much less of an issue when working in the street, for example, at f 5.6 or 8 when the subjects are further away.

The EVF is more accurate at close distances even with narrow DOF.

 

[Godfrey]

The real issue is that neither rangefinder nor focus peaking are critically accurate focusing aids. Focus peaking is dependent upon the camera's processor being able to distinguish local edge contrasts and exaggerate them .. And those edges are not necessarily the optimum focus plane. RF accuracy is dependent upon the optical and mechanical calibration of the whole system, from lens to viewfinder patch, which as we all know has many sources for error.

I use both in my photography with the M-P, but I don't spend time comparing them. Each requires different technique and interpretation to achieve the best results. Knowing and becoming skilled in either, and understanding specific lens behavior, is the way to critically accurate focusin with an M.

G

 

[jaapv]

As opposed to focusing, Godfrey is spot-on... 😀

 

[johannielscom]

It's just that at close distances with f2 the DOF is narrow. The narrow DOF mean any inaccuracy in the optical/mechanical RF becomes more important.

By contrast any RF inaccuracies are much less of an issue when working in the street, for example, at f 5.6 or 8 when the subjects are further away.

The EVF is more accurate at close distances even with narrow DOF.

On my iPhone I use an app called SimpleDoF.

It states that on 35mm frame size, a lens 2.0/50mm focused at 1.70 meters distance, produces 13.5cm DoF. At 1.20 meters away, this reduces to 6.6cm DoF.

Personally, I feel neither of these two are too limiting, I can keep myself from swaying 3 inches while shooting a portrait and five inches could fit a lorry😉

Wider lenses yield even more DoF at the same distances.

Testing a new M240 for focus is misguided and splitting hairs, IMHO. Just my two cents of course. 😀

 

[chaospress]

Testing a new M240 for focus is misguided and splitting hairs, IMHO. Just my two cents of course. 😀

"Just wanting to determine if my rangefinder is off because the camera was delivered, let's say, not that well packed"

 

[jaapv]

On my iPhone I use an app called SimpleDoF.

It states that on 35mm frame size, a lens 2.0/50mm focused at 1.70 meters distance, produces 13.5cm DoF. At 1.20 meters away, this reduces to 6.6cm DoF.

Personally, I feel neither of these two are too limiting, I can keep myself from swaying 3 inches while shooting a portrait and five inches could fit a lorry😉

Wider lenses yield even more DoF at the same distances.

Testing a new M240 for focus is misguided and splitting hairs, IMHO. Just my two cents of course. 😀

"Within DOF" is not sharp. It is the area where the photographer determines that the unsharpness is acceptable.

Aditionally, DOF is not an on/off effect, it increases and decreases gradually.

A photograph is only sharp in the plane of focus.

 

[johannielscom]

"Within DOF" is not sharp. It is the area where the photographer determines that the unsharpness is acceptable.

"within DoF" is sharp enough. Nothing wrong with that, is there? Let's not get too academical on 'sharp' please...

Aditionally, DOF is not an on/off effect, it increases and decreases gradually.

A photograph is only sharp in the plane of focus.

That would seriously limit Leicas chances to get you a sharp picture then, since there is gear play involved in any mechanism, per your own words.

'Sharp' also is not an on/off effect in real life photography. Enter contrast, circle of confusion regarding print size, etc.

I still think it's splitting hairs. Go out and shoot, and see if you like what you get, what else was the darn thing made for?