Hyperfocal anomaly on my copy of Nikon 16-35 AFS

[habsphoto]

<p>I just got my D800E and 16-35 back from Nikon Pro service in El Segundo.<br>

I did a test in my living room indicative of the kinds of interiors I normally photograph because I am trying to understand some of the results I am getting in the field.'<br>

In a typical interior room 10-15 or so feet from the subject, the lens displayed no front focus at all as you would expect using Hyperfocal focus. The area behind the focus point (AF and LV) was sharp (as much as you would expect at a given f-stop like f11) but there seemed to be no gain in focus in front of the focus point. The old two thirds back and one third in front does not seem to apply to my copy. Now this is a physically long superwide zoom and seems to define the meaning of RETROFOCUS (about 170mm between end of lens and sensor). So I can imagine that some of the standard limitations and predictable behavior of a 16mm lens may be put aside to point the light at the FX sensor. (as much as the laws of physics can be bent) Curious if anyone else has found similar behavior in their copies? This will obviously change what I choose to focus on when composing future architectural interiors, as I will begin to focus on the closest point and not 1/3 into the scene. </p>

[jose_angel]

<blockquote>

<p><em>there seemed to be no gain in focus in front of the focus point....</em></p>

</blockquote>

<p>That`s normal up to a certain ammount. If you`re at the widest setting, the DoF is distributed more or less as you say. The defocus behind the escene will increase gradually (that is, maybe with a higher perception of sharpness), while in front the increase will be steeper.</p>

[alan_olander1664878205]

<p>Hyperfocal technique includes infinity. With interiors where there is nothing at infinity, using hyperfocal distance would be a waste of DOF. Selecting a focal point where the DOF includes the near and far elements of the room would be the best technique, which it sounds like you're doing. The design of the lens would not alter the DOF. Perhaps your lens is not focusing correctly.</p>

[elliot1]

<p>Just curious why you had to send your camera and lens in for service...</p>

<p>Jose, shouldn't the area in focus be equal both in front of and behind the point of focus?</p>

[mike dixon]

<i>shouldn't the area in focus be equal both in front of and behind the point of focus?</i><P>

At very close focus distances, the DOF extends a roughly equal amount in front of and behind the plane of focus. As the focus distance becomes greater, the DOF behind the plane of focus becomes progressively greater than the DOF in front of the plane of focus. The "1/3 in front, 2/3 behind" is a rough guideline that is only accurate at a particular focus distance for a particular focal length.

[keith_b1]

<p>To clarify Mike's point, '1/3 in front + 2/3rds behind' is not a "law of physics".<br>

Like most depth of field info, it's just made up stuff that might have worked for somebody once upon a time, but may or may not work for you in a given situation with given equipment.<br>

You're on the right track to conduct your own tests and create your own method that works. </p>

 

[jose_angel]

<p><strong>Elliot</strong>, shorter lenses are more assimetrical in that distribution than longer lenses. And there is an specific situation here; as far as the focus distance is closer to the hyperfocal distance for a given aperture, the DoF distribution also increase that assimetry.</p>

<p>Steve says he is using an "hyperfocal focus" method, that I understand he is simply setting a calculated or aproximated distance on the barrel and the correspondant aperture (he says f11?).</p>

<p>Think that the hyperfocal will give him the highest assimetrical DoF distribution; infinity at the back, a bit more than one meter at the front... it is way more than 2/3 - 1/3!</p>

<p>Just focus a little closer than the hyperfocal distance, and the distribution changes dramatically, getting gradually closer to that "rule". What Mike says.</p>

<p>Don`t know at what precise distance Steve has placed the plane of focus, he says 10-15 feet, so his experience seem quite normal to me. It certainly could fit the "law of physics".</p>

[elliot1]

<p>Jose, thanks for the explanation.</p>

[habsphoto]

<p>Thanks for the noodleing of this issue. I sent my Camera and lens in for focus check with the lens and to have the oil spots cleaned from the sensor. I had the time and it was under warranty.<br>

I'll do some more tests but Im finding that I'm getting less than an inch or two of depth in front of the focus point and about 3 feet behind... at around 9' away from the subject.</p>

[rodeo_joe1]

<p>Whether a lens is of retrofocus, normal or telephoto construction should make almost no difference to its depth of field. Otherwise relative aperture numbers would be next to useless. The solid angle of the cone of light projected from a lens at infinity focus is simply given by: 2*arctan(1/(2*f_number)). This is regardless of focal length or type of lens.</p>

<p>However, images from the D800E are capable of a huge degree of magnification, and at 100% viewing you’ll see that the DOF is almost non-existent at any aperture or subject distance. Depth of field really is in the eye of the beholder, and almost impossible to properly quantify numerically.</p>

[rodeo_joe1]

<p>Sorry, attempted to attach a DOF calculator in XLS format to previous post, but file format isn't allowed, so:<br>

Attached is a screenshot from my DOF calculator. The calculator uses the same circle of confusion (0.029mm) as Nikon uses on the DOF markings of its full-frame prime lenses. The same c-o-c, or very close, is used by many other makers and calculator programs. As stated above, such numbers can only be a rough guide since DOF depends on viewer preference and viewing magnification.</p><div></div>

[habsphoto]

<p>The more I work with the 16-35 the more I think that the D800E just has a hard time determining focus in any interior light situation on single point AF. Like a medium format digital, the D800E does a stunning job when tethered and carefully focused on subjects in a magnified Live-View setup. But my AF experience is hit or miss.</p>