Focus beyond the infinity stop - 35/2 asph

[marcg]

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I've just bought a new (secondhand lens) which seems to be in new condition. 35mm cron 6bit.

 

When I focus it through my M7 on, say, a church steeple 100metres or more away, the steeple comes into focus about a fraction before the infinity stop and then seems to go a hair out of focus as the infinity stop seems to go beyond that point.

 

Have I explained the problem well enough?

 

Does anyone recognise this?

 

I haven't had time to run some film through yet so I am only able to talk about what I see through the viewfinder.

Ta

[masjah]

Try checking against the moon (I'm not being facetious here). Infinity is a long way away, and it may be that the church steeple isn't quite far away enough to count as infinity.

[marcg]

I'll try it. Thanks.

Cloudy tonight, though.

[earleygallery]

100m isn't infinity, it will be fine I'm sure.

[tobey bilek]

Use a star. 100 meters is NOT infinity

[jhild]

the moon or a star are to far away, something like 5 - 600 meters is much better. If the rangefinder

and/or the lens are ok everything from about that distance has to be sharp in the rangefinder. Try it

with a SLR if you have one and you will see what I mean, but don´t use a 200mm lens on the SLR.

Coming back to your 35mm lens, even if it´s that little wrong as you describe it you should be ok.

Check it with slide film at f2 at 36 different settings on 36 different objects on 36 different distances...

 

have fun

 

Jo

[jhild]

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I forgot, lenses of different lenght have different distances where they reach their infinity point. For the

35 Summicron have a look at the Leica homepage.

 

Jo

[marcg]

I forgot, lenses of different lenght have different distances where they reach their infinity point. For the

35 Summicron have a look at the Leica homepage.

 

Jo

 

Thanks for this. I'm noty sure that I have looked in the correct place. I downloaded the tech data for the lens but couldn't notice the info there.

[menos I M6]

Thanks for the clarification here.

Now it dawns me, what I have recognized with my 35 Cron too.

 

The 35 Cron ASPH does focus "slightly beyond infinity", compared to my 50 Lux ASPH.

With the different focal lengths this makes now perfect sense.

 

As both lenses focus plenty sharp at close and medium focus distance, both should be ok then.

[marcg]

However, the fact is that this particular Leica 35/2 Summicron-M was not in critical focus at its infinity stop, but the Zeiss 35/2 Biogon was, and that makes a huge difference, and it’s highly relevant to making real images. In this case, my analysis suggests that the Leica 35/2 Summicron-M infinity stop is actually slight beyond infinity.

http://diglloyd.com/prem/prot/DAP/LeicaM9/compare35.html

 

 

 

 

These reviews are some of the best I have found on the internet - although they are for subscribers.

 

If you want to read some really no-holds barred reviews of the M9, some Leica lenses and other topics then this is certainly one place to look.

 

His conclusions about the 35/2 are very interesting and certainly seem to tie up well with the comments which have been made about this lens on this forum.

 

It seems that the answer may simply be that this is street shooters lens not really what you might want for infinity focus/planar jobs.

Horses for courses.

 

The 35/2 maybe better also for low light work than the Zeiss which is used as the comparator in the review.

[E.M]

I may be wrong , but I have been tought that infinity for a 35 mm lens is 35 meters , for a 50 mm it is 50 meters , and so on .

 

Etienne Michiels

[tobey bilek]

If you focus on a star and focus at 35 meters, it will be different.

 

There is no way for an object to be beyond infinity.

[normclarke]

The industry recognised formula for camera lenses is 1000XF/L = infinity.

 

Best,

 

normclarke.

[E.M]

Well , that's what I said , but in other words. But I am not 100% sure it's correct.

 

Etienne Michiels

[Mike Rawcs]

If you focus on a star and focus at 35 meters, it will be different.

 

There is no way for an object to be beyond infinity.

 

Buzz Lightyear regularly goes to infinity - and beyond!

 

 

(laughing) Mike.

[rob_x2004]

You arent asking about focus you are asking about rangefinder alignment.

Yes it seems normal that careful focus throught the 0.72 rangefinder at fifty, seventy five, a hundred meters brings the lens up short of its maximum stop.

There is no infinity mark on the lens, its a ∞ about three and a bit millimetres long.

[pinetar]

I read where focus beyond infinity is engineered in by Leica to allow for expansion and contraction of components do to hot and cold.

[wizard]

I read where focus beyond infinity is engineered in by Leica to allow for expansion and contraction of components do to hot and cold.

 

True, but only for some telephoto Leica-R lenses, not for Leica-M lenses. The rangefinder concept does not allow for this, you need an SLR to take advantage of any focus beyond the infinity mark.

 

Andy

[redbaron]

What are those advantages? Very curious.

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Hallo,

Look here: Interesting Leica gear

[masjah]

What are those advantages? Very curious.

 

It's more a question of building in an ability to cope with large temperature changes (thermal expansion and so on) with long lenses. The question only arises with an SLR simply because such long lenses do not exist in the M system.