Interesting LFI article

[dhsimmonds]

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In the current August issue of LFI is an interesting article describing the phenomonom of Focus Shift with Leica optics on digital cameras. It is directed at M8 users but I believe it could well be of interest to DMR users and in fact it is even mentioned in another article in the same issue about the V-LUX-1 bridge camera.

 

Leica lenses are designed to focus accurately at their maximum aperture and experience a shift of focus when stopped down. This phenomonom is not seen with film bodies but since the introduction of the M8 it is very noticeable but only with the faster lenses.

 

The solution recommended with the V-LUX-1 which is auto focus, is to use the handy macro focus when stopping down regardless of the focus distance. ( I wonder if this phenomonum is also true of the D2/LC-1?)

 

M8 users are encouraged to use maximum aperture for focusing.

 

I am also wondering now if this also applies to the faster R lenses when used with the DMR back or even the D3?

 

I must go back over some of my dodgier focused images to check their apertures in the exif data. I do tend to stop down a bit from max. aperture whenever the required DOF is a bit tight, so I might inadvertently be making the situation even worse?!

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[carstenw]

Both M8 users and DMR users would focus wide open, although DMR users could stop down to see if the focus plane has shifted. The rangefinder doesn't look through the lens, and doesn't know the value of the aperture setting, and SLRs always focus wide open and then stop down to take the shot.

 

Autofocus cameras like the Digilux-3 may do a little focus adjustment after stopping down, just before shooting, I don't know.

[marknorton]

Autofocus cameras like the Digilux-3 may do a little focus adjustment after stopping down, just before shooting, I don't know.

 

Carsten, I'd be surprised. Cameras with smaller sensors and shorter focal length , slower lenses have greater depth of field so focussing is much less of an issue.

 

I think the LFI article is just re-iterating everything we've seen discussed on this board with the 35mm/1.4 ASPH being a prime example.

[carstenw]

Yes, LFI recently has published many articles based on the rumblings of this forum... I am not sure if I like this trend. They are good articles, well written, on interesting topics, but by the time they appear in print, we have usually covered them in depth here. They usually manage to add something, but relatively little in comparison to the scope of the full article. I also find it a little surprising that they don't write that the topic started here, but rather refer to anonymous "internet forums".

[marknorton]

Yes, LFI recently has published many articles based on the rumblings of this forum

 

I "hear" they're planning to publish a complete list of lens codings next and they're even planning to take an M8 apart. LOL.

[jaapv]

Yes, LFI recently has published many articles based on the rumblings of this forum... I am not sure if I like this trend. They are good articles, well written, on interesting topics, but by the time they appear in print, we have usually covered them in depth here. They usually manage to add something, but relatively little in comparison to the scope of the full article. I also find it a little surprising that they don't write that the topic started here, but rather refer to anonymous "internet forums".

 

Not all LFI subscribers are on this forum, not even a small percenatge , I guess. So it is not redundant. As for the contents of the article, I found it adressed some aspects that had not been discussed here, like adding a floating element in the lens design to combat focus shift.

[ho_co]

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Yes, LFI recently has published many articles based on the rumblings of this forum.... They usually manage to add something, but relatively little in comparison to the scope of the full article....

Not all LFI subscribers are on this forum, not even a small percenatge , I guess. So it is not redundant....

It's good that our explorations lead to their officially making an explanation available, though there's a sense that we're getting less for our subscription fee if in some sense we helped write the article.

 

But in any event, it's good to see a public confirmation and clarification of our speculations.

 

I "hear" they're planning to publish a complete list of lens codings next and they're even planning to take an M8 apart. LOL.

 

Mark, you could ask if they're going to use the same brand camera as you for the macro shots. Apparently when the first Leicaflex came out, the product photos were shot with an Alpa, so technically they wouldn't be breaking new ground.

 

--HC

[jaapv]

It's good that our explorations lead to their officially making an explanation available, though there's a sense that we're getting less for our subscription fee if in some sense we helped write the article.

 

Maybe we should apply for a collective reduction of our subscription fee

[zapp]

The focus shift article did not shed much new light on the story. i was amazed that they needed 3 pages for an intro and 3 pages for an extroduction, telling us that Leica is great, and only two pages about the real problem, looking at a single lens.

Focus shift may really be worse for short focal length lenses, since very small shifts in the focus plane relate to large shift in the distance setting.

[guywalder]

I for one am happy to see issues being followed up in LFI, its as near to an 'official' explanation as we could expect.

However I have to say that in this case I find the summary completely disingenuous!

'here is the problem, here is what it looks like, here is how we avoided it in newer designs, now dont worry about it 'cos its not significant' !!

[modschiedler]

I think they tried to avoid emphasizing the focus shift aspect too much (esp. in the M8 context) since they may have feared that what people might keep in mind then would be "hey, focussing with the M8 is next to impossible, why should I spend my money on it?". So in order to not damaging Leica here they decided to embed the topic into something dealing with the M and with M lens design in general thus also explaining en passant why focus shift is inherent in high speed high class designs. Remember they have the red dot on their cover, although they are officially independent. A published print article works differently compared to quick discussions in a net forum. Of course they use forums as sources of inspiration, why not? As mentioned, there are lots of readers not being active in internet discussions.

cheers,

mjm

[modschiedler]

I for one am happy to see issues being followed up in LFI, its as near to an 'official' explanation as we could expect.

However I have to say that in this case I find the summary completely disingenuous!

'here is the problem, here is what it looks like, here is how we avoided it in newer designs, now dont worry about it 'cos its not significant' !!

 

Hi Guy,

I would put it differently. What they have said is: Yes, focus shift sometimes is a problem, and yes, Leica is aware of it, and this is why they introduced floating elements. Considering older designs however the only thing to do is to keep the phenomenon in mind while using the lens. It is not a bug (although no feature anyway) but simply something you have to deal with when you want high performance at large apertures at large field angles. What kind of summary would you have expected other than explaining why and when focus shift occurs? Something like "here comes another disaster, better send your lenses to CS (in order to recalibrate them at cost of full aperturte performance) or change the system"?

cheers

[carstenw]

LFI is a third-party magazine, so what happens here is just as official. I think the positive benefit of seeing the material covered in LFI after we hash it out here is that they have better access to inside information, and can flesh some things out that we can only guess at. Still, not all their re-hash articles add much to what was found here.

[guywalder]

marc-jürgen,

I was refering to the sentance:

'In der Alltagspraxis mit dem 35er dürfte der Verschiebungseffekt kaum fotografisch relevant sein'

Given the amount of coverage they have given the problem, and the amount of hoo haa leica like to make about the excellence of their lenses (which are excellent!), I find that sentance a joke. Otherwise it was an interesting article

Guy

[carstenw]

It does depend a bit on what they meant with "dürfte", and also with respect to what. It also stuck out to me when I read the article, but it is at least theoretically possible that they meant with a proper adjusted lens, and were not referring to some of the clearly troublesome 35 Luxes we have seen around here. Even with a properly adjusted lens, the effect is still there, just within reason.

[modschiedler]

If I look at their example shot I cant’t help but conclude that it indeed seems to be not that relevant in practice, esp considering how you use a 35 in most cases, i.e. as a reportage lens. I presume one will find the effect of minmal camera shake or slight defocusing more often on one’s photos than a disturbing effect of focus shift. Thus the article puts the phenomenon into perspective, maybe as a kind of response to the sometimes exaggerated oops urgh published here. Just my two cents.

[carstenw]

Yes... as long as you remember that some lenses have much more focus shift than the one in the LFI article. Tim's long thread showed a horrifying amount of shift which is by no means acceptable, and Leica was unable to/refused to fix the lens.

[guywalder]

If I look at their example shot I cant’t help but conclude that it indeed seems to be not that relevant in practice, esp considering how you use a 35 in most cases, i.e. as a reportage lens. I presume one will find the effect of minmal camera shake or slight defocusing more often on one’s photos than a disturbing effect of focus shift. Thus the article puts the phenomenon into perspective, maybe as a kind of response to the sometimes exaggerated oops urgh published here. Just my two cents.

 

err do you think that they would choose examples to make it look as bad as possible?

I suspect not!

As Carsten says, there is variation from lense to lens (not addressed in the article..), but also one thing I found when I first got my D2x was not so much the difficulty of accurate focus with MF lenses, as how obvious it was when I missed focus. This was invariably because apart from my intended target not being really sharp, something else in the picture usually Was really sharp, because of that 'digital' look, and viewing everything at 100%. The LFI example may not be showing that as clearly as some other subjects might have done.

As for it not mattering 'cos its a reportage lens, well why pay 3 grand if you are not bothered about ultimate lens performance?

Guy

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Hallo,

Look here: Interesting Leica gear

[earleygallery]

M8 users are encouraged to use maximum aperture for focusing.

 

I don't understand why it matters what aperture you use on an M camera as the rangefinder is simply working off the cam, there's no way of the physical aperture setting affecting the rangefinder??

[Lucklik]

The solution recommended with the V-LUX-1 which is auto focus, is to use the handy macro focus when stopping down regardless of the focus distance. ( I wonder if this phenomonum is also true of the D2/LC-1?)

 

!

 

Regarding the Vlux 1 I understood the following.

The focus area of the Vlux 1 is quite big.

In AF mode the AF has the tendancy to focus on the things (in the focus area) which are far away.

In AF Macro mode the AF has the tendancy to focus on the things (in the focus area) which are close,

I'll have to try it.

rgs

 

Luc