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Focus distance markings accuracy?


lincoln_m

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With a 35f2asph on my Sony A7 I've just noticed that when I focus through the EVF on an object 5m away the marking in the lens says 3m. I used an f4 aperture so the focus point is more obvious. Very distant objects are in focus when the lens says 10m. On my MP using the rangefinder it seems the actual focus distance and the markings agree, although that's is down to the accuracy of the rangefinder setup. I assume the difference I see using the A7 is down to the back focus distance and the M bayonet adapter. What it means is that I can't use the infinity setting on my lens as that is "past infinity" and results in everything being out of focus. With the A7 I have to focus with the EVF as I can't rely on the distance markings.

 

Has anyone measured the in focus distance of a digital m and checked it against the distance markings on the lens? I always assume that the distance markings would be spot on when m lenses are used on m cameras, I have no reason to suspect otherwise but this test with the A7 has me wondering how accurate the distance markings are. With my film Ms over 15 years the focus and the markings seem to match, I can set to infinity and the hyper focal distance seems to be what I get back on the film.

 

With the A7 I get distant objects in focus when set to 10m but not if I set to infinity. Same goes for 50f2 at f4 or f8 so this is not to do with focus shift and aperture as what I see is a much bigger effect.

 

So if I bought an M10 I hope I'd have accurate match between the markings and the actual focus?

 

Cheers Lincoln

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3 meters against 5 real and 10 against infinity ? As above said... it can be only the adapter... These are not slight tolerances on which one could discuss if the distance is from focal plane or lens' center or some other point... a Summicron 35 asph simply cannot be so out of range , even if heavily used... and the fact that on your M the distances are reasonalbly correct is a further proof of this.

Edited by luigi bertolotti
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pop, my Leica M to NEX adapter says "K&F cOncept" on it. I think I bought it on Amazon. It does the job I won't change/alter the adapter as I do get sharp images most of the time (if I don't use the scale on the lens) especially now I know of the limitation.

 

I don't think SONY make an adapter but they do have links with Zeiss who make many lenses for the SONY. But I don't want to have to buy Zeiss 35, 50mm lenses for the SONY.

 

I suppose it's good it's this way so at least I can get infinity in focus for landscapes. I just know now not to trust the distance markings on the lens when using the M lenses on the Sony A7 and M-NEX adapter. To be safe I have to use the pixel peeping zoom in via the EVF to get the focus I want. I am using an £800 A7 body because I didn't want to spend £6K on an M10 or even £3500 on a thick M240 so I guess I have to expect some compromises.

 

My hidden question is do M lenses on M digital cameras, focus exactly where the scale says? You'd have to have an M with live view (M240, M10, M262) or an EVF connected to rule out the possible inaccuracies of the rangefinder in the focus/distance/lens markings equation? Has anyone checked? Focus on a door 2m away does the rangefinder focus and the live view focus agree with the 2m on the lens scale? Is that 2m to the front of the lens or the back of the camera?

 

The rangefinder can get knocked and become out of calibration (expensive to have Leica CLA) but the lens focus should always match with the distance marks on the lens, right? With film & scanner & the rangefinder all adding focusing tolerances it's harder to notice if things are wrong (one may blame yourself for an unsharp image) but with digital live focus the final image file should have the same focus as seen in live focus.

 

One option for me to move to a Leica digital but not cost the full £6K might be the Leica SL full frame with no low pass filter on the sensor but to use my M lenses. That would also require an M-adapter L and even with Leica parts the worry may be that the M lenses on the SL may not be setup as well as M lenses on an M digital, because of the extra adapter and the added tolerances, sort of similar to my A7 + M-NEX + M lenses.

 

(It seems that M-adapter T is actually the same as the M-adapter L if the T bayonet and SL bayonet and dimensions are the same?)

 

For M film landscape photography the infinity setting or using the hyperlocal is accurate enough but for close-up <3m subjects we have to focus with the rangefinder especially when using wide apertures as even the hyperlocal on a 35mm at F2 has narrow DOF, +/- 20cm at 2m. Using a summilux or noctilux wide open focusing with the rangefinder must be difficult to guarantee accurate results particularly for portraiture. I can see the appeal of the SL EVF for Professional Photographers and that's partly what attracted me to the Sony A7 (the hi-res EVF) even if the manual focus process on the A7 is slower. Going back to using the film M rangefinder it seems so much faster but possibly less accurate.

 

Thanks in advance for your thoughts on M240, M10, SL rangefinder focus accuracy when compared with live view and the lens markings.

Lincoln

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Looks like Sony has nothing to do with how RF lens works on RF. Or even on simple scale focus camera. 

 

And I'm not so sure what extremely wide apertures has any advantage for the portraiture. RF or else. But you don't need focus scale focusing method for it for sure.

Edited by Ko.Fe.
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As far as I know, the distances engraved on the barrels of Leica M lenses are accurate. They refer to the distance from the object to the film or sensor plane. Unfortunately, the plane is not indicated any more on more recent cameras, it appears.

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Hello Everybody,

 

It has been my experience with "M" film cameras that you can use a properly calibrated range/viewfinder to measure accurately with. Even with 35mm lenses.

 

You can use the back end of the rail for the accessory shoe for a "close enough" film plane.

 

There is no reason that the rangefinder in the range/viewfinder of a digital "M" camera should measure any differently.

 

Best Regards,

 

Michael

Edited by Michael Geschlecht
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Not to dispute the bad adapter theory, but I'd note that DoF at 10m/f4 for 35mm per these guys is:

 

Near Limit 11' 2" ( 3.4 m ) Far Limit 30' 12" ( 9.44 m )

at f2:

Near Limit 13' 3" ( 4.05 m ) Far Limit 21' 5" ( 6.54 m )

 

If you're relying on focus peaking, in my experience, when stopped down, you can easily be fooled into thinking your dead on the mark when you're not really.  Personally when focusing via evf, I'm always wide open and then stop down, if need be, to take the shot.  

Edited by Tailwagger
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It’s a too thin adapter. Used many and they all vary.

 

Yes, M lenses are correct on a digital M10.

 

You can shim the adapter (most people do) to get infinity right. This is necessary with FLE lenses since they adjust the floating element(s) based on the focus setting and need it to be right to correct lens performance correctly.

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The more I look at my photos using A7 and 35F2asph or the 50F2 I see that only f8 gives good images anything wider has issues in the lower corners where the ground is out of the DoF. The adapter is most likely the issue along with the wider angle of the light rays. 35 mm is worse and 50mm is better.

 

I'm beginning to think I don't invest anymore in the A7 but start saving for a Leica M digital. The Leica SL would also need an M adapter-L to use my M lenses and that might have a similar issue if that adapter was not perfect. It's a big step from £800 A7 to £6000 M10.

 

Or I forget about digital and just shoot film instead and put up with the chroma noise from my Minolta Elite 5400 scanner from 2003? It would probably take me 10 years to spend the £5000 difference on Provia and E6 processing compared to the digital M, longer if I get back to developing my B&W myself.

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I would acquire a good adapter to begin with. Now if you have an A7 already why don't you have it modded by Kolari Vision? My A7s mod works fine with the 35/2 asph and most of my 30+ Leica lenses. The SL must be as good or better i guess but i have no experience with it. 

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All adapters will allow the lens to go past infinity. That's how they get away with having loose tolerance.

 

Also, if your adapter is cheaply made then it may have issue with uneven thickness causing slanted image plane. Reason to use a good adapter or use a native mount camera.

Edited by jmahto
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Although my adapter seems well made it was only about £20. As you guys say it might be worth buying the Novoflex version at £140 if the distances are more precise then hopefully the real distance marks will match the focused distance and the optics might be better aligned to give improved IQ at the edges for wider apertures than f8.

 

Or if that doesn't work splash out on a used SL with Leica adapter for M lenses, but now we're at £4000.

 

Maybe try the novoflex adapter first?

Lincoln

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The Novoflex adapter works fine but won't make your stock A7 behave like a Leica or a modded Sony. As you can see below, even my Kolari mod A7s may show softer corners with the 35/2 asph at f/2. There is no free lunch.

https://www.l-camera-forum.com/topic/249421-sony-fans-show-your-sharp-corners-with-m-r-wides/page-2?do=findComment&comment=2979362

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lct, Your images are much cleaner with sharp focus in the corners than my current adapter gives. I can only describe it as looking like camera shake as you get to the corners (> 12mm radius from the centre) I think the chromatic aberration is also much worse in the corners for my A7 and K&F adapter. If the lens is not focusing the image on the sensor correctly because of the very slightly wrong adapter thickness then I could imagine these issues and the fact that f8 is OK because of the DoF but f4 is not, makes sense. Your setup is obviously more finely tuned. I just get a harsh blur in the corners for close objects outside the main centre focus hyperlocal DoF.

 

If the Novoflex allowed me to use f4 with better IQ for £140 that might be worth it as I'm effectively at f8 for good IQ on the 35F2Asph now and anything wider just looks nasty in the corners. If that doesn't work then I think I'll stick with film Ms for the next few years until the used prices become sensible.

Thanks all for your inputs.

Lincoln

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