D800, 85mm 1.4G and focus shifting.

Started May 15, 2012 | Discussions
JMacedo
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D800, 85mm 1.4G and focus shifting.
May 15, 2012

Two days ago I bought a 85mm 1.4G and so far I am still very impressed with its performance, see my thread here,
http://forums.dpreview.com/forums/readflat.asp?forum=1021&message=41499491

My first shooting was all done at F1.4 except one pic shot at F4.5, looking at that F4.5 pic I could see some backfocusing and i was scratchin my head why!

Decided to test the lens agains a chart using F4.0 and to my surprise this new lens was in need of a -18 fine-tune adjustment!!

Went to the streets to try the lens again after the -18 adjustment made and the shooting was a total disaster, all my f1.4 shots were sort of way to soft with some frontfocusing and the ones stopped down extremely sharp!!!

Did some more tests and the focus shift is so evident that I thought something was wrong with the lens.

Suddenly I remembered to have read something about this in the Photozone review of this lens ( http://www.photozone.de/nikon_ff/606-nikkorafs8514ff?start=1 ) but at the time I didn't pay too much attention to it.

I don´t think this have any impact when shooting peoples' portraits but nonetheless I would like to share this little issue I bumped into. Maybe one day Nikon will release better fine-tune in firmware with the possibility to make adjustments for more than one focal lenght

This is the problem with too much pixel-peeping the D800 pics! lol

In the case of the pic where I noticed this, I was on an over pass bridge and shot a bus on a street below. The bus is not in focus but the farthest buildings are.

Here is the pic and crops where I noticed the focus shift:

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Jorge Macedo
http://www.jmacedophotography.com

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inasir1971
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, May 15, 2012

Hi JMacedo,

Focus shift is one of the issues with fast primes. Here is the focus shift pattern for the 50 1.4G and 50 1.8G (download the originals to see full vertical resolution).

Hopefully, there is a 'window' where all apertures will be in focus - this is usually going to mean adjusting your focus point further back when wide open. At wide apertures, focus shift is greater than increasing DOF, and at smaller apertures increasing DOF is greater than focus shift. After you fine tune your AF, you need to check if in focus from wide open to around f4, after that increasing DOF more than compensates for any focus shift effects...

Hope that helps...

EDIT: Focus shift moves the focus point backwards, away from camera, as lens is stopped down...

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jason_z
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Re: D800, 85mm 1.4G and focus shifting.
In reply to inasir1971, May 15, 2012

What's a practical solution? Focus bracketing?

I experienced an even stranger behavior using 85mm at 1.4 in Live View. Most pictures are front focused. How can Live View create a front focus with this lens?

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JMacedo
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Re: D800, 85mm 1.4G and focus shifting.
In reply to inasir1971, May 15, 2012

Thanks inasir,

This is my first prime (not counting the Tamron 90 mm macro) and I wasn't fully aware of focus shift with primes, after your explanation I checked the Photozone reviews for other primes and this is a fact even the new 85mm 1.8g has the same focus shift.

This is not an issue for me as I intend to use this lens wide open for my candid street shots, I am covered by the 70-200 VRII for other type of shots at the 85mm focal lenght.

First time I looked at the pic I thought; Oh No! the left AF issue is back again! as I used the leftmost focus point to take the posted pic! lol
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JMacedo
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Re: D800, 85mm 1.4G and focus shifting.
In reply to jason_z, May 15, 2012

I would like to see Nikon implementing better lens fine-tuning for different f-stops and focal lenghts (thinking about zooms)

jason_z wrote:

What's a practical solution? Focus bracketing?

I experienced an even stranger behavior using 85mm at 1.4 in Live View. Most pictures are front focused. How can Live View create a front focus with this lens?

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Jason

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mark kay
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Re: D800, 85mm 1.4G and focus shifting.
In reply to inasir1971, May 15, 2012

The other approach is to focus at the max aperture 1.4 or 1.8 and then change the aperture to what you really want to shoot at. You have to make sure the camera is set so that as you re-press the shutter button you are not refocusing.I guess you can set AF lock while you adjust the aperture.

inasir1971 wrote:

Hi JMacedo,

Focus shift is one of the issues with fast primes. Here is the focus shift pattern for the 50 1.4G and 50 1.8G (download the originals to see full vertical resolution).

Hopefully, there is a 'window' where all apertures will be in focus - this is usually going to mean adjusting your focus point further back when wide open. At wide apertures, focus shift is greater than increasing DOF, and at smaller apertures increasing DOF is greater than focus shift. After you fine tune your AF, you need to check if in focus from wide open to around f4, after that increasing DOF more than compensates for any focus shift effects...

Hope that helps...

EDIT: Focus shift moves the focus point backwards, away from camera, as lens is stopped down...

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inasir1971
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Re: D800, 85mm 1.4G and focus shifting.
In reply to mark kay, May 15, 2012

mark kay wrote:

The other approach is to focus at the max aperture 1.4 or 1.8 and then change the aperture to what you really want to shoot at. You have to make sure the camera is set so that as you re-press the shutter button you are not refocusing.I guess you can set AF lock while you adjust the aperture.

That wouldn't work as the change in focus point is caused by the lens being stopped down - it's not any movement, it's a change in the lens behavior as it's stopped down...

Liveview focus in 'A' or 'M' mode will work as the aperture is stopped down while focusing is done unlike PDAF where focusing is done wide open.

JMacedo, the examples I posted above are what I used and the lens is in focus at all apertures - you just need to set your tuning to something similar.

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AtomicPunk
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, May 15, 2012

JMacedo wrote:

Two days ago I bought a 85mm 1.4G and so far I am still very impressed with its performance, see my thread here,
http://forums.dpreview.com/forums/readflat.asp?forum=1021&message=41499491

My first shooting was all done at F1.4 except one pic shot at F4.5, looking at that F4.5 pic I could see some backfocusing and i was scratchin my head why!

Decided to test the lens agains a chart using F4.0 and to my surprise this new lens was in need of a -18 fine-tune adjustment!!

Went to the streets to try the lens again after the -18 adjustment made and the shooting was a total disaster, all my f1.4 shots were sort of way to soft with some frontfocusing and the ones stopped down extremely sharp!!!

Did some more tests and the focus shift is so evident that I thought something was wrong with the lens.

Suddenly I remembered to have read something about this in the Photozone review of this lens ( http://www.photozone.de/nikon_ff/606-nikkorafs8514ff?start=1 ) but at the time I didn't pay too much attention to it.

I don´t think this have any impact when shooting peoples' portraits but nonetheless I would like to share this little issue I bumped into. Maybe one day Nikon will release better fine-tune in firmware with the possibility to make adjustments for more than one focal lenght

This is the problem with too much pixel-peeping the D800 pics! lol

In the case of the pic where I noticed this, I was on an over pass bridge and shot a bus on a street below. The bus is not in focus but the farthest buildings are.

Here is the pic and crops where I noticed the focus shift:

-- hide signature --

Best regards,

Jorge Macedo
http://www.jmacedophotography.com

Jorge...thanks for sharing everything, including the other thread. I am seriously considering this lens for portraits. One quick thing. Since you took your landscape photo in this thread in portrait mode, was the focus point the one at the bottom? In other words, would this be the far left AF sensor if you had the camera in landscape orientation? If so, this may be the issue with the left AF point. I notice the same thing when using that left AF point. It tends to back focus. Maybe your 1.4 shots didn't use that AF point.

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mark kay
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Re: D800, 85mm 1.4G and focus shifting.
In reply to inasir1971, May 15, 2012

OK agreed-- I guess you would have to manually focus with aperture preview at the aperture you plan to shoot at then.

inasir1971 wrote:

mark kay wrote:

The other approach is to focus at the max aperture 1.4 or 1.8 and then change the aperture to what you really want to shoot at. You have to make sure the camera is set so that as you re-press the shutter button you are not refocusing.I guess you can set AF lock while you adjust the aperture.

That wouldn't work as the change in focus point is caused by the lens being stopped down - it's not any movement, it's a change in the lens behavior as it's stopped down...

Liveview focus in 'A' or 'M' mode will work as the aperture is stopped down while focusing is done unlike PDAF where focusing is done wide open.

JMacedo, the examples I posted above are what I used and the lens is in focus at all apertures - you just need to set your tuning to something similar.

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Dominique Dierick
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Re: D800, 85mm 1.4G and focus shifting.
In reply to AtomicPunk, May 15, 2012

I wouldn't be to worried about this lens, if you know there is a bit of focus shifting, you can work around. Same thing with the 50mm for instance.

Here is a 85 1.4G image I made during a game (was for a newspaper), using left AF point, with detail inset.

Jorge...thanks for sharing everything, including the other thread. I am seriously considering this lens for portraits. One quick thing. Since you took your landscape photo in this thread in portrait mode, was the focus point the one at the bottom? In other words, would this be the far left AF sensor if you had the camera in landscape orientation? If so, this may be the issue with the left AF point. I notice the same thing when using that left AF point. It tends to back focus. Maybe your 1.4 shots didn't use that AF point.

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JMacedo
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No left AF issue, I think.
In reply to AtomicPunk, May 16, 2012

AtomicPunk wrote:

Jorge...thanks for sharing everything, including the other thread. I am seriously considering this lens for portraits. One quick thing. Since you took your landscape photo in this thread in portrait mode, was the focus point the one at the bottom? In other words, would this be the far left AF sensor if you had the camera in landscape orientation? If so, this may be the issue with the left AF point. I notice the same thing when using that left AF point. It tends to back focus. Maybe your 1.4 shots didn't use that AF point.

Hi,

Yes, I used the far left sensor and my D800 had the left AF issue but I believe it was fixed by Nikon, see this my other thread:

http://forums.dpreview.com/forums/read.asp?forum=1021&message=41384338

You can clearly see how the focus shifts using the 85mm 1.4 here:
http://www.photozone.de/nikon_ff/606-nikkorafs8514ff?start=1
The same happens with other primes.

I just did a quick handheld test and as you can see my camera is fixed, no more Left AF issue here but I do feel for the people still dealing with the issue.

Ok, hazy Bangkok, taken from my balconi, handheld, camera exposed a little different but you can see there's no focus difference between Leftmost and Rightmost focus points.

Leftmost focus point @ F1.4:

Crop Leftmost focus point@F1.4:

rightmost focus point @ F1.4:

Crop rightmost focus point@F1.4:

A slight different exposure (these were taken handheld and the weather was changing quickly) but the focus is similar in both pics.

Left vs right

============================================
=
= Similar results using F4
=
============================================

Crop Leftmost focus point@F4:

Crop rightmost focus point@F4:

Left vs right @ F4

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Jorge Macedo
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JMacedo
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Re: D800, 85mm 1.4G and focus shifting.
In reply to Dominique Dierick, May 16, 2012

Hi Domminique,

No, I am not worried but I confess I was surprised as this was my first prime. I have no intention to use this lens at other F stop than F1.4, I love the effect it gives wide open, despite not being the sharpest thing.

Easy to work around and I also own the 70-200 2.8 VRII that i think is more appropriated for pics like the one in my original post. Thanks.

Dominique Dierick wrote:

I wouldn't be to worried about this lens, if you know there is a bit of focus shifting, you can work around. Same thing with the 50mm for instance.

Jorge...thanks for sharing everything, including the other thread. I am seriously considering this lens for portraits. One quick thing. Since you took your landscape photo in this thread in portrait mode, was the focus point the one at the bottom? In other words, would this be the far left AF sensor if you had the camera in landscape orientation? If so, this may be the issue with the left AF point. I notice the same thing when using that left AF point. It tends to back focus. Maybe your 1.4 shots didn't use that AF point.

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JacquesBalthazar
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Re: D800, 85mm 1.4G and focus shifting.
In reply to Dominique Dierick, May 16, 2012

Is that Palm in that glass?

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Dominique Dierick
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JacquesBalthazar, May 16, 2012

Yes
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falconeyes
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In reply to JMacedo, May 16, 2012

Thanks for the report. I know about the issue. However, I am still learning about Nikon and I wonder what is going on here.

E.g., I know that e.g., Pentax for the DA 21mm Ltd. lens compensates for the lens' focus shift in firmware. This is the obvious thing to do of course. Because focus shift is caused by spherical aberration which is part of the optical formula and very well known a priori.

So my question is:

Does Nikon lack indeed a proper treatment of focus shift in it's frmware?

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phototrope
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, May 16, 2012

No harm in using the 85/1.4g at apertures greater than 1.4 for outdoor shots. It just requires smaller apertures than f/4.5 sometimes to get more depth of field. Look at a DoF field calculator and familiarise yourself with the scale for the 85mm lens.

The beauty of just using a prime (or two) for long periods is that you can really study the lens characteristics, know exactly its strengths and weakness and use it to its greatest advantages. Field curvature, flare, vignetting, though considered weaknesses by naive testing can all be used to great advantage. IMHO, this is why they can potentially yield better results.

Or the other way is to concentrate on just one aspect of the prime's strengths, eg wide open performance - a good way to start.

JMacedo wrote:
Hi Domminique,

No, I am not worried but I confess I was surprised as this was my first prime. I have no intention to use this lens at other F stop than F1.4, I love the effect it gives wide open, despite not being the sharpest thing.

Easy to work around and I also own the 70-200 2.8 VRII that i think is more appropriated for pics like the one in my original post. Thanks.

Dominique Dierick wrote:

I wouldn't be to worried about this lens, if you know there is a bit of focus shifting, you can work around. Same thing with the 50mm for instance.

Jorge...thanks for sharing everything, including the other thread. I am seriously considering this lens for portraits. One quick thing. Since you took your landscape photo in this thread in portrait mode, was the focus point the one at the bottom? In other words, would this be the far left AF sensor if you had the camera in landscape orientation? If so, this may be the issue with the left AF point. I notice the same thing when using that left AF point. It tends to back focus. Maybe your 1.4 shots didn't use that AF point.

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Jorge Macedo
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The Big One
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, May 16, 2012

JMacedo wrote:

I would like to see Nikon implementing better lens fine-tuning for different f-stops and focal lenghts (thinking about zooms)

+1. My consumer level Olympus cameras (E-620, E-30, equivalent to D5100 and D7000) from a few years ago allowed AF fine tune at wide and long (with a linear function to transform between the two). There is no reason that Nikon's pro and semi pro cameras should not do the same, if not better. It is all software: they could implement it today in the D7000 as a firmware update!
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mdcphoto
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, Jun 22, 2012

I've noticed this too, but I didn't realize that it was aperture related. Bummer. I have also found that the lens hunts endlessly for focus if the subject is closer than 10 feet. Have you noticed this on yours?

thanks,
Mike

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vincenzo torsello
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Re: D800, 85mm 1.4G and focus shifting.
In reply to JMacedo, Apr 8, 2013

I spent days trying to fine tune all my lenses (all about -20), with poor results, not good for all apertures.

Finally I tried the DEFAULT setting, removing all saved values for each lens, putting just -8 as default.

All lenses now give perfect focusing, at all apertures and focal length, tested with Lensalign!

Maybe this is not the solution for all cases, but I suggest to try!

Vincenzo

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