Hi Glenn & Les,
Pouring rain in Ballarat today so the focusing tests have been thoughtfully/carefully, rescheduled for the indoors. . .
Bruce

Hi Guys,
We live in interesting times. I set out today to try and set the AutoFocusFineTune on my D500+300mm F2.8+1.4X T/C combination.
I conducted 12 tests under the AFFT system and discounted the highest and lowest numbers for a total of+49 or an average of +5, showing a front focusing result.
I then went to adjust the setting to compensate for the front focusing issue and I hadn't noticed before but the setting, for some reason, was already at +8 ?? This was a brand new camera in a brand new box, perfectly packaged and certainly not showing any sign of having being opened and used before ??
I then took 5 images of a home-made 'Lens Align' set-up and after downloading the images into Lightroom and checking the point of focus under 2:1 magnification, it was clearly evident that this lens was focusing consistently between 3-4cm in front of the target.
I have reset the positive setting to +4, which is half of the figure that the camera was set to, and I will repeat the same 5shot test tomorrow and check the results?

The set-up for indoors was tripod with heavy sandbag, camera set to F4 (minimum with teleconverter), S/S 1/250 with SB5000 flash unit and Self Timer for release. . .

Bruce

Glad to hear you've made progress - sounds like you may have fixed the softness problem you were having?

Hi Bruce,

You mentioned the aperture setting used with your 300 mm f/2.8 + 1.4x but not the distance between the camera and test target.

For technical reasons there will be a small variation of the AFFT required depending upon aperture and distance to the test target. Canon recommend the distance to the target should be about 50 x effective focal length = 50 x 420 mm in your case or about 21 m. Unless you have a big house, this is not easily achieved indoors and for this reason I do my tests outside where I am fortunate to have a long enough concrete deck. It makes a good optical bench and I can use sunlight to illuminate the test target..

The aperture used for AFFT is also important. If you have a sensitive AFFT setup you will be able to clearly see a difference between the AFFT required at full aperture and when closed down a stop. For this reason, I usually do my adjustment with the aperture closed down one stop which will be closer to the aperture I usually use in the field. I very rarely use any of my lenses at full aperture because the depth of field is usually too small to get all the bird in sharp focus. So for your 300 mm f/2.8 + 1.4x I would do the AFFT at aperture f/5. You will find there is very little variation of AFFT for f/5 - f/11 but there will be a measurable difference between f/4 and f/5.

There can also be a slight variation in AFFT depending upon the light source. This is usually a very small effect and provided you have enough light to use a reasonable ISO, say less than ISO 800, it will not be an issue. If you can test outside using direct sunlight, this will be the perfect light source. One general comment about outdoor testing; try to do the tests in the morning before your test range gets too warm. If you are testing over a warm 21 m surface you may find the AFFT results vary alarmingly; to avoid this problem it is best to do the testing in the morning. However, with the kind of weather we are currently experiencing in Victoria, it will make no difference whether you are testing in the morning or afternoon but in the summer it will usually only be possible to get consistent results during the morning.

Hope this helps, good luck,

Ian

Hi Guys,
Hi Ian and welcome back. . .
I thought that I was making progress but I better start again?
Ian, the ISO was 400 and the distance only 9meters, so I better take it outside tomorrow?
Bruce

Hi Bruce,
I have all three Nikon TCs and each needed a quite different adjustments on the camera when using the D300. However, the 300 F2.8 VRI by itself needed no adjustment at all out of the box. I'm curious if your lens is correct before you add the TC? My particular TC20EIII need the maximum adjustment allowed for by the camera, and for a while i considered getting it re-adjusted by Nikon, so this would be less extreme. The TC17 is the TC I use most often and needed only a touch of correction.
Something else you might consider, are you using VR when conducting your tests? I find the VR collapses immediately after taking a shot with flash, using either the F800E or my old D300, which is why I avoid using flash during tests. if i were unhappy with the results I'm getting from my lens, I would test it with and without VR, just to rule out a problem with it. The camera is mean to adjust its VR when it's on a tripod. The general consensus of opinion the I last paid attention to discussion about VR and shutter speeds, is that it becomes a hindrance to image sharpness once you set your speed above 1/800th of a second.
Cheers