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24-90mm Focus Shift (Diglloyd)


agencal

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It's hard to respond about an alleged fault when it isn't referred to for what it is. AF focus error is in no way "focus shift". 

That's another negative point for Digilloyd in my book. 

 

Confirms nothing new for me, however. AF is a useful convenience when it works, and is rarely as consistent or accurate as manually focusing a lens. AF can focus more quickly than manual focusing for some situations and subjects, so it is occasionally useful to have it available. I generally don't rely upon it for much other than snapshooting.  B)

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It's starting to appear that Lloyd was doing a pretty extreme parfocal stress test.  Zoom all the way in to auto-focus, then zoom out to see if the result is still sharp and looking at the same place by magnifying the result.  Maybe he has some more tricks that he has found.  Would you guys pay $90 to find out about these, especially since Leica will have corrected them in firmware?  What I resent is that Lloyd's "squeaky wheel" may have gotten greased before much more relevant concerns (e.g. R lens profiles that were not checked properly) that are brought up in the open forum environment.

 

scott

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I think his unfortunate use of terminology does not stop at "focus shift". I think that when he refers to "zooming in" he actually means "focus magnification", not zooming. This sort of sloppiness is what causes major bust ups between me and my wife as well :unsure:

Edited by LocalHero1953
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Easy enough for it to happen with AF.  The camera simply isn't focusing where you told it to.  It's focusing slightly "below" (in the viewfinder).

 

- Jared

 ..... which is what occurred to me ...... but using the camera upside down seemed  to produce the same result ...... which is why I discounted this as the cause. Having said that I only took a few frames of portrait format and upside down so it wasn't a rigorous test. 

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 ..... which is what occurred to me ...... but using the camera upside down seemed  to produce the same result ...... which is why I discounted this as the cause. Having said that I only took a few frames of portrait format and upside down so it wasn't a rigorous test. 

 

It also occurred to me . . . . It just seemed that it might be the whole focus 'box' rather than the cross hairs in the middle . . . . . until I read your 'upside down' test, and as I trust you implicitly thighslapper I left it at that. . . . . . . .  ;)  :p  :D

 

My testing was quite rigorous, and I'd come to the conclusion that the focus point was towards the front of the area in focus . . .but I think everyone here had come to the conclusion that it was quite within any normal photographic requirement (and I still firmly believe that). I've been getting cracking, sharply focused results from day one, and perhaps that's the real criteria. .  . . .  . 

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I think his unfortunate use of terminology does not stop at "focus shift". I think that when he refers to "zooming in" he actually means "focus magnification", not zooming. This sort of sloppiness is what causes major bust ups between me and my wife as well :unsure:

I thought that "joke camera" and "OMG" were pushing the boundaries a bit as well  :)

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The problem here is that it is not the first time.

 

The Q was a POS because he made a user error, the MM1 got hammered  ("I have to investigate") because he had never heard of a focus shift due to the use of a deep red filter on a non-APO lens (and even APO sometimes), etc.

 

And always he is "working with Leica to solve the problem".

 

Still, I guess he is anticipating on the findings of his audience.

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The man has to eat.  Blandness = starvation.  He has always been accident prone.  Often he will push a product outside its intended use envelope, and complain about a lack of perfection.  Lately, he has been eulogising Zeiss lenses (with some justification, but without revealing what appears to be an indirect commercial relationship with the company).  (Witness his slagging of the 35mm Leica FLE v 35mm Zeiss, to the extent that I am always  very pleasantly surprised with my FLE results  :D )

 

This makes his reviews less than useful to me, as I am more interested in real world use characteristics, ergonomics, etc, which he does cover, but there is a fairly low signal to noise ratio.  That said, there are few alternative sources of information in specialised products such as the Leica.  Sean Reid offers a painful site interface experience and tests with lenses that do not really fall into the mainstream.  At least he offers a suitably Jerry Springer like window into the real USA, I suppose.  Thomsen offers some good raw data, but his epic whimsey lacks focus.

 

In the end, there is nothing much better than sticking to what you know and like, and occasionally playing with new toys / tools as they become available, using your own experience of what matters (i.e., understanding the limitations of your current setup) to decide whether they could suit you.

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(I don't own SL but curious)

Doesn't SL body has AF fine tune capability?

Yes it does, if I understand the question correctly. You press the shutter release half down to activate AF, then holding the shutter release down, fine tune the focus using the focus ring on the lens.

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I think his unfortunate use of terminology does not stop at "focus shift". I think that when he refers to "zooming in" he actually means "focus magnification", not zooming. This sort of sloppiness is what causes major bust ups between me and my wife as well :unsure:

 

I think you (and others) are a little bit unfair here, regarding his use of focus shift terminology.

 

Chambers said clearly in his first post to the issue that:

 

"I experienced consistent problems in the field with both autofocus and focus shift. Both issues are extremely serious in that they destroy image quality." 

 

To my understanding now we have news regarding the first problem, not yet to the second problem. I am sure he talked to Leica on this second issue of focus shift also. Maybe the origin of the problem is even the same. 

Edited by siddhaarta
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The problem here is that it is not the first time.

 

The Q was a POS because he made a user error, the MM1 got hammered  ("I have to investigate") because he had never heard of a focus shift due to the use of a deep red filter on a non-APO lens (and even APO sometimes), etc.

 

And always he is "working with Leica to solve the problem".

 

Still, I guess he is anticipating on the findings of his audience.

 

I think for once he is correct and there is something rather odd  here ...... although it takes quite careful testing to sort out what exactly is going on. 

 

I would have expected the point you are focussing on with AF to be bang in the middle of the DOF range at that aperture, but in fact the target point is towards the very back end of the DOF range....... only just in focus and certainly not the optimal focus point. 

 

I did some slightly more accurate tests tonight ...... this was the target .....quite a steeply raked document at about 2m ....... focus point fairly obviously the X in the box .....

 

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Edited by thighslapper
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This is f4 and the second f11 ...... cropped to show the DOF and focus more clearly .......

 

 

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These are with the camera upside down ........ then the images turned the right way up ......

 

first is f4 again and the second f11 ......

 

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This is what DGL is wittering on about ...... at the two available magnifications ....  AF  focussed then zoomed in ......

 

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You can draw your own conclusions as to whether DGL has a point or not. 

 

I can't see much focus-shift as such though, certainly not enough to cause issues if AF was accurately calibrated.....

 

The difference ..... or lack of much of a difference when the camera is inverted is rather perplexing.

 

..... and mismatch of AF point when magnified is too small to explain all of what is going on.... 

 

When inverted it jumps from Long-Eared to Tawny Owl as expected......

 

I don't understand enough about AF to supply any answers ......

 

plus ..... there is no documentation indicating the actual size of '1 point AF' .... or its shape and orientation  ..... and these tests (and those by others) are for quite close distances for a 90mm lens ..... and lens characteristics do vary with distance .... so the observed effect here may be absent or less  at mid and far distance..... 

 

ps ...... I have most of the Owl and Hawk Wood Engravings by Colin See-Paynton ...... nice bloke and fantastic artist ...... they were a steal at this price (a good few years ago now)  :)

Edited by thighslapper
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oh .... and I've taken and posted loads of pics with the 24-90 ..... mostly wide open ....... and I have yet to find one where I can honestly say the effects above have compromised the image  ...... and if it was a problem I would have a hard drive full of duds ..... but the reverse is the case ..... a very small % of technically poor images, certainly in comparison to other cameras I have used.....

Edited by thighslapper
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Way too much time and insanity spent on this stuff for me. 

 

Where the AF system sets its focus has an element of judgement in it. Frankly, setting it to the rear quadrant of the "acceptable focus" zone actually makes some sense to me ... I'm much more distracted by unsharp things in the foreground than in the background, unless I'm shooting scenics at or near infinity—and why on earth would I use autofocus for that?  

 

My tests of focus shift with the 24-90 prove to me that, on my unit of this lens anyway, it has no to negligible focus shift at all marked focal length settings. 

 

So is it a bug, or a miscalibration of the AF system, or a decision on the part of Leica as to how to use AF with deep DoF? I don't know, and I really don't care that pixelbators like DigiLloyd get all up in arms about how the AF focusing doesn't match their personal expectations. I haven't seen any photographs "ruined" by the AF system yet in any of my or example photos made with the lens.

 

Pick up your cameras and lenses, charge up your batteries, and go out and study your subjects more than you're studying your cameras. That's how you get better photos.  :rolleyes:

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  • 1 month later...

Hmmm, got mine a week ago and gave it its first proper workout yesterday. Pretty much every shot at the long end was quite noticeably soft. With a deep sigh at why something that costs this much should require me to do so, I will now try to bottom out what is going on. But from looking at the leica provided MTF graphs, this isn't just a lens that's 'not quite as good at the long end as in the middle' - it's a lens that is unacceptably soft at the long end, even were it a cheap lens, and is clearly underperforming its spec for whatever reason.

 

Will report back. 

Edited by tashley
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