ssmc
Well-known
My D700 (bought new) had an extremely annoying maladjustment between the VF and (very accurate) AF - when the VF showed a sharp image, the capture would be slightly OOF, and vice-versa. This problem absolutely drove me nuts and after a lot of testing and renting several lenses (Zeiss 100/2, Nikkor 135/2 DC and Sigma 150/2.8 macro) I eventually determined the focusing screen needed to be re-shimmed.
To cut to the chase, re-shimming the focusing screen was a total success and a lot easier than I expected. Other than being careful to handle the shims without bending or dropping them, it's really no more difficult than changing screens (just more time-consuming). By far the worst part was getting rid of the tiny specks of dust/lint/whatever that find their way onto the screen and the base of the prism while it's all apart, but repeated use of the Rocket blower and the L1 LumaMax eventually got it all spotless (shining the L1 through the eyepiece revealed the exact location of any dust on the prism).
Here is a pic of the setup I used: the small blue tool is for releasing the screen retaining wire (this one came from KatzEye), the Pec-Pad is to put the screen on (shiny side down) while it was out of the camera, and the tea-towel was to rest the body on upside-down to stop the shims dropping out; the steel rule was taped down at both ends and the desk lamp just provided a bit more light on the markings. I used a Tokina M100 as it is extremely sharp, the FL made seeing the rule markings much easier, and it has a very long focus throw. At this distance the widest this lens goes is f/3.5 but that still gives a pretty shallow DOF; a 50/1.4 would have been even better but then I would have needed a magnifying eyepiece to get decent accuracy. I wore non-powdered rubber gloves for the whole procedure and cleaned the tweezers with 100% isopropanol beforehand.
Whatever lens you use (an 85/1.4 would be great...), make sure to shoot it wide open or focus shift will confound the results!
The shims are color-code but for some weird reason the part # sequencing does not correspond to an increase in thickness:
1K603-374 - 0.15mm (copper)
1K603-373 - 0.20mm (brass)
1K603-372 - 0.10mm (silver/chrome)
1K603-384 - 0.05mm (copper - but easy to tell apart from the -374's as they are paper-thin)
I focused on the 500mm line as best I could in the VF and then switched to LV to check where it was really focused (in this case, about 5-6mm further away), repeating the process several times for each shim pack. This camera had 1x -373 shim and 1x -384 shim installed from the factory (0.25mm total). I'd already determined that since the VF was back-focusing, it required more/thicker shims, so I removed the -384 (only) and tried each successive thickness until I got it right - or as close as it could be given the limited range of thicknesses available. I ended up with 2x -373 shims (0.40mm total) - quite a large increase from the original. When this camera was sent to Nikon to have a few hot pixels mapped out under warranty they also adjusted the AF and it came back absolutely spot-on - I am stoked to report that I can now say the same about the viewfinder 😀
While this may look/sound daunting, anyone who has replaced a focsing screen could do this job, and (IMO) any serious users of manual-focus lenses should check their camera for VF/AF agreement and think about shimming it if they need to (go easy on the caffeine beforehand, though 😉). Considering I bought 2x sets of shims (which Nikon call "washers") for AUD23.68 (I didn't know what I was going to need and there was always the possibility of damaging one), this has to be the best-value upgrade to this camera I can think of, since I can now accurately focus MF lenses, even long ones, and tweaking AF-S lenses can now be done with complete confidence in the results - finally, WYSIWYG!
Hope someone finds this info useful
Scott
To cut to the chase, re-shimming the focusing screen was a total success and a lot easier than I expected. Other than being careful to handle the shims without bending or dropping them, it's really no more difficult than changing screens (just more time-consuming). By far the worst part was getting rid of the tiny specks of dust/lint/whatever that find their way onto the screen and the base of the prism while it's all apart, but repeated use of the Rocket blower and the L1 LumaMax eventually got it all spotless (shining the L1 through the eyepiece revealed the exact location of any dust on the prism).
Here is a pic of the setup I used: the small blue tool is for releasing the screen retaining wire (this one came from KatzEye), the Pec-Pad is to put the screen on (shiny side down) while it was out of the camera, and the tea-towel was to rest the body on upside-down to stop the shims dropping out; the steel rule was taped down at both ends and the desk lamp just provided a bit more light on the markings. I used a Tokina M100 as it is extremely sharp, the FL made seeing the rule markings much easier, and it has a very long focus throw. At this distance the widest this lens goes is f/3.5 but that still gives a pretty shallow DOF; a 50/1.4 would have been even better but then I would have needed a magnifying eyepiece to get decent accuracy. I wore non-powdered rubber gloves for the whole procedure and cleaned the tweezers with 100% isopropanol beforehand.
Whatever lens you use (an 85/1.4 would be great...), make sure to shoot it wide open or focus shift will confound the results!
The shims are color-code but for some weird reason the part # sequencing does not correspond to an increase in thickness:
1K603-374 - 0.15mm (copper)
1K603-373 - 0.20mm (brass)
1K603-372 - 0.10mm (silver/chrome)
1K603-384 - 0.05mm (copper - but easy to tell apart from the -374's as they are paper-thin)
I focused on the 500mm line as best I could in the VF and then switched to LV to check where it was really focused (in this case, about 5-6mm further away), repeating the process several times for each shim pack. This camera had 1x -373 shim and 1x -384 shim installed from the factory (0.25mm total). I'd already determined that since the VF was back-focusing, it required more/thicker shims, so I removed the -384 (only) and tried each successive thickness until I got it right - or as close as it could be given the limited range of thicknesses available. I ended up with 2x -373 shims (0.40mm total) - quite a large increase from the original. When this camera was sent to Nikon to have a few hot pixels mapped out under warranty they also adjusted the AF and it came back absolutely spot-on - I am stoked to report that I can now say the same about the viewfinder 😀
While this may look/sound daunting, anyone who has replaced a focsing screen could do this job, and (IMO) any serious users of manual-focus lenses should check their camera for VF/AF agreement and think about shimming it if they need to (go easy on the caffeine beforehand, though 😉). Considering I bought 2x sets of shims (which Nikon call "washers") for AUD23.68 (I didn't know what I was going to need and there was always the possibility of damaging one), this has to be the best-value upgrade to this camera I can think of, since I can now accurately focus MF lenses, even long ones, and tweaking AF-S lenses can now be done with complete confidence in the results - finally, WYSIWYG!
Hope someone finds this info useful
Scott
