D800 & LensAlign

Started Apr 28, 2012 | Discussions
Stangs55
Stangs55 Regular Member • Posts: 482
D800 & LensAlign

After reading Luminous Landscape's glowing praise for the LensAlign, I decided to pick one up this weekend since I've always suspected that my 70-200 VR I was just a touch off.

We'll now I've got a couple more questions than answers...below are two 100% crops from my sample pictures without any AF adjustments.

1. Backfocus? Frontfocus? Yea...I can't really tell. I think the 70-200 is backfocusing.

2. Is it me, or is there a helluva lot of CA in these shots...?...and that's really the reason I'm posting this in these specific forums. I haven't had much time at all to shoot with my D800...but these first controlled tests are worrisome to me.

Nikon D800 @ ISO 100. f/2.8
JPEGs straight out of the camera.

Nikon 24-70 at 70mm and 5.7 ft

Nikon 70-200 at 200mm and16.4 ft

Nikon D800
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PHXAZCRAIG
PHXAZCRAIG Forum Pro • Posts: 19,054
Re: D800 & LensAlign

The first shot looks pretty even to me. Look at the smallest numbers you can make out, starting with the blurry ones and moving in.

The second one has pretty clear backfocus.

CA is always going to look worst in these conditions. Absolute black/white transition, wide open, looking into the out-of-focus areas too. I'd say it's normal, though I don't know what's normal for the 70-200. My 24-70 looks close to what your image shows.

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Robin Casady Forum Pro • Posts: 12,898
Re: D800 & LensAlign

I see a tiny amount of front focus in the first image—about 2. The second image has a serious amount of back focus—somewhere around 20.

The exposure looks off. I'd shoot it in NEF and use Lightroom 4 with lens corrections off. There is some indication that Capture NX2 is doing some blurring to reduce aliasing. The same thing may be happening with JPEGs.

I'm wondering if there is some motion blur in the second photo? Did you use a heavy-duty tripod with mirror lock up?
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lefty from Saratoga Contributing Member • Posts: 613
Re: D800 & LensAlign

I agree there is back focus showing on your 70-200 and the 24-70 might have just a smidgeon of front focus, probably not enough to worry about.
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Vancouver Regular Member • Posts: 237
Re: D800 & LensAlign

You may want to get a Focus Pyramid from http://www.focuspyramid.com

It worked great for me.
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Cliff Beard Regular Member • Posts: 461
Re: D800 & LensAlign

I calibrated my AF lenses on my D300, D700 and D7000 bodies, including the lenses you show here.

Most combos were back focusing to varying degrees, requiring between -2 to -9 correction.

You 70-200 is back focusing a fair bit, the 24-70 looks ok.

I found that overexposing slightly and boosting contrast/sharpening helped determine the exact focal plane in the trickier assessments. Its easier to see on very wide aperture lenses like f1.4.

Some lenses will seem a bit lacking in in contrast when tested wide open, with both lateral and longitudinal CA showing. In fact the latter can help you assess focus as green fringing tends to form behind the focal plane and red in front of it. If you have red bleeding over your zero and even beyond, its likely to be back focusing. I think you may have some motion blur in shot 2 which makes the image soft.

I note that your focus target is misaligned (not level) in both posted shots. Its worth being as accurate as you can be to minimise errors caused by misalignment or the sensor not focusing exactly on the target. Defocus the lens between shots too. One lens I tested gave really inconsistent results (although only slightly off) but most were pretty consistent in the type of misfocus and the amount.

I think calibration is a avery worthwhile exercise, especially if you shoot wide apertures a lot. Some camera/lens combos were so unreliable I didn't trust them at all before calibrating.
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Christian Wagner Senior Member • Posts: 1,547
Re: D800 & LensAlign

Vancouver wrote:

You may want to get a Focus Pyramid from http://www.focuspyramid.com

Thanks for this link. Been looking for something cheaper then the lensalign.

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Chris
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Robin Casady Forum Pro • Posts: 12,898
Re: D800 & LensAlign

Christian Wagner wrote:

Vancouver wrote:

You may want to get a Focus Pyramid from http://www.focuspyramid.com

Thanks for this link. Been looking for something cheaper then the lensalign.

The problem with using a slanted AF target is that the viewfinder rectangles for AF don't exactly match the AF points. So, you never really know where the AF point is hitting.

If you want cheap, you could try this:

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

Or, print your own AF target and ruler. A little carboard, spray adhesive, and you are good to go.
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Georgino Regular Member • Posts: 381
Re: D800 & LensAlign

24-70 little front focusing

70-200 (you done something wrong here) the image is not even sharp
use tripod, lockup mirror, use cable release or timer

The images doesn't even look like you level it ether.

Make sure you level your focus chart and camera as well

Try again and post image here

Take care and good luck

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kenwj Contributing Member • Posts: 573
Re: D800 & LensAlign

You can't do it like that!!! Go into Photoshop and run a "Find edges" filter on the images. You will be able to tell in a heartbeat.

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Christian Wagner Senior Member • Posts: 1,547
Re: D800 & LensAlign

Robin Casady wrote:

Christian Wagner wrote:

Vancouver wrote:

You may want to get a Focus Pyramid from http://www.focuspyramid.com

Thanks for this link. Been looking for something cheaper then the lensalign.

The problem with using a slanted AF target is that the viewfinder rectangles for AF don't exactly match the AF points. So, you never really know where the AF point is hitting.

I'm not totally following. How would you not know where the af point is hitting?

And how is lensalign different? That is slanted too no? Or do you have the same issue with LensAlign?

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Chris
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inasir1971
inasir1971 Veteran Member • Posts: 4,098
Re: D800 & LensAlign

Looks like back focus (for some reason most lenses seem to be doing this with the D800).

The CA you see is axial CA because that area is OOF - this is the one-time in life where it is actually useful, the color telling you which it is.

EDIT: Please to check your final setting by testing all apertures from wide open to f4 or f5.6 to make sure that focus shift doesn't move your target OOF - particularly for fast lenses (1.4 etc.)

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inasir1971
inasir1971 Veteran Member • Posts: 4,098
Re: D800 & LensAlign

you'd really want to do this shooting JPEG's with all corrections turned off.

The distance to use is usually 25 x focal length. For zooms, midpoint or the end you use most.

LensAlign is different because it provides a target that is perpendicular to the camera (the vertical target) and thus parallel to the sensor. Best $80 I've spent on my camera...

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Robin Casady Forum Pro • Posts: 12,898
Re: D800 & LensAlign

Christian Wagner wrote:

Robin Casady wrote:

The problem with using a slanted AF target is that the viewfinder rectangles for AF don't exactly match the AF points. So, you never really know where the AF point is hitting.

I'm not totally following. How would you not know where the af point is hitting?

You aim the camera at the pyramid's sloping chart. You adjust the camera so the focus bar on the pyramid is in the center of the focus point square in the viewfinder. Right?

What if the point where the camera actually focuses is a little above the center of the square? Your camera will be focusing on something above the focus bar and it will appear that your lens is back focusing when actually it isn't.

And how is lensalign different? That is slanted too no? Or do you have the same issue with LensAlign?

LensAlgin has a vertical card to focus on and a slanted rule to judge actual focus. The vertical card is inline with the 0 focus point on the rule. So, your AF sensor and AF indicator box can be a little out of alignment, but you will still get an accurate result.

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Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 23,651
Re: D800 & LensAlign

The problem with the OP is he/she is not testing to a good enough standard to get a reliable result - which probably explains why one shot might be -2 and the other +20.
Results like this are usually 99.99% likely to be due to poor technique.

The problem With LensAlign is the AF target is a geometric pattern - Nikon caution in the D800 instructions and on the web geometric patterns sometimes cause focus error https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/4585
I do not see good value in paying $80 for a sometimes unreliable target.
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lanef Forum Pro • Posts: 10,317
Re: D800 & LensAlign

Vancouver wrote:

You may want to get a Focus Pyramid from http://www.focuspyramid.com

It worked great for me.

The focus pyramid cannot be reliable because the target focus is at an angle not perpendicular to the lens, the LensAlign is the proper tool for that kind of test.

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http://www.flickr.com/photos/38519080@N00/sets/72157594443652688/

tektrader Senior Member • Posts: 1,768
Re: D800 & LensAlign

When I first tried Lensalign with my 28-70 and 70-200. I got interesting results for CA.

The 28-70 f2.8 showed similar CA to your photo which I was a bit taken aback by. However the 70-200 even at 200% was perfect, No CA and still sharp.

BUT I made the observation that figuring out the focus point using the slanted scale at F2.8 isnt all that easy. There is still a large amount of DOF which makes the actual centre point quite difficult to see. This is very easy to adjust wrong wth micro focus.

I was a bit surprised as the lens align samples show a very narrow DOF and easily seen focus poiint. I put it down to their sample photos being done with F1.8 lenses.

I did this with a d7000. It will be interesting what my D800 needs when I finally get it.

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CFynn Veteran Member • Posts: 5,225
Re: D800 & LensAlign

Vancouver wrote:

You may want to get a Focus Pyramid from http://www.focuspyramid.com

It worked great for me.

This looks pretty good too...

http://www.reikan.co.uk/focal/

Uses a vertical target and some sophisticated software to align your lens.

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marike6 Veteran Member • Posts: 5,088
Re: D800 & LensAlign

The 24-70 doesn't seem to have frontfocus or back-focus very much, if at all.

I would reshoot the second test with a tripod, center AF as there is almost nothing in focus in the test image. I defy anyone to find the AF point. In the first image, you can clearly see the plane of sharpest focus, but in the second, it doesn't seem to exist.

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lanef Forum Pro • Posts: 10,317
Re: D800 & LensAlign

The 24-70 is too close to call, I would leave it as it is, the 70-200 seems to have some back focus.
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