Thursday, August 26, 2010

Adjusting the Nikon D300 Auto Focus system

Caution: I am not a repair technician. This is just what I did on my own D300 body.

First, there are two hex screws inside the mirror box on the left side (right side as you're look face-on at the camera). The one closest to the mounting ring adjusts the focus of the AF-focused image on the viewfinder's screen. It provides the mirror's stop position. The second, and more important screw is behind the main mirror, and adjusts the stop for the AF system mirror. This is the main one you'll want to adjust if you're having a focus issue.

Use a fixed focal length lens. Use a fixed focal length lens. Use a GOOD fixed focal length lens. If you don't have one (which is known to be properly calibrated) go and rent one. I had months of trial-and-error using my reasonably-expensive Sigma 70-200mm f2.8 lens until I realized that it was subject to about a 1.5" focusing error at 6 feet (minimum focusing distance for that lens). Using my 50mm f1.4 was a cinch, and I ended up finally nailing the focus in just a few minutes time with it. Once you have it set at a small, but sharp f-stop (I used f2.0 on my f1.4 lens, it still has very narrow depth of field), check it with all of your lenses (and teleconverters).

The hex screws work on eccentric-shaped pins. Moving the hex wrench up moves the pin back, moving the hex wrench down moves the pin forward. There is a VERY small range of adjustment needed to move the focus point quite a bit. For the front hex head, up on the stop pin moves the focused image closer to your eyeball. Down on the stop pin moves it farther from your eyeball. It is a reflected image off the mirror, after all. Attention: Do not adjust this until AFTER the camera is taking sharp photos, confirmed on your monitor. For the rear hex head, down on the pin moves the focus FARTHER from the camera, while up moves it CLOSER to the camera. In this case you are moving the image forward and back on the focus sensors mounted in the floor of the mirror box. Hopefully your lens is doing its best to resolve the image properly at the sensor plane.

If you find you're taking big swings at it, something is wrong with your lens (as I figured out somewhat late). Any focusing error up close will be grossly magnified when shooting in the distance. If you optimize your AF system witha front-focusing lens, shooting at infinity will be impossible (it will all be blurry).

On the bright side, if you've gotten to the point where you want to try this and you simply cannot send your camera to Nikon for 3 weeks, give this a shot. It's fairly difficult to massively screw up your camera beyond the point it already is, and if you do, there's always Nikon Service to fix it.

BTW-I used both the "Sensor Cleaning Mode" to adjust the screws and occasionally simply lifted the mirror carefully with my finger and used the allen key on it. Be prepared to have to dust off your sensor if you use the "Sensor cleaning mode" as all sorts of dust will land on it while the shutter is open.

Good luck!

Wednesday, August 25, 2010

More Nikon Autofocus thoughts

First, never attempt to reset your focusing with a zoom lens. My 70-200mm f2.8 Sigma has a close-focusing error at minimal focus distance, and this was causing me to screw up my attempt to reset my AF system on my D300. I was zooming in on something close (to better see where the area of sharp focus was). Once I went to the Nikon 50mm f1.4 body, things went much smoother. Now I'm getting pretty much laser-like images, all the way down to wide open settings, so I'm much happier.

Second, using single-point AF in the dark sucks on the D300. Cars in the darm (on a lit track) must not offer as much contrast for a single point to grab onto. Eventually I went to the 9-point grouped sensor setting and began to get sharp photos. It's very frustrating switching through the modes and getting shot after blurry shot. The 51-point "3D mode" simply does not work well for cars. There's too much area covered by the points, and it often grabs focus on a point outside the area the car occupies, resulting in out-of-focus photos. At a track, where there's often a white wall visible in the dark, the Nikon AF will CONSISTENTLY find that white wall in 51-point mode. Grrrrrrrrr. 9-point AF works well. I'd love to see Nikon add a 15-point mode, where it adds 3 more sensors to the left and right of the 9-point square, for a more horizontal configuration friendlier to cars. I don't need the additional 6 vertical points of the much slower-to-focus 21-point mode. Pretty please, Nikon? Can I have this in the next software update? I'm sure no one is reading this blog.

Third, though my 50mm f1.4 is the sharpest lens I own by far, its incredibly-slow focusing system will NOT capture cars in real-time. I discovered this in Long Beach in April, at the Formula Drift event, and rediscovered it in Las Vegas last weekend. My cheap 18-55mm Nikon "kit" lens is faster (though not by much). As a result I wound up using my much heavier Sigma 70-200mm f2.8 lens through the night. Boy did this make my arms tired!

That's all for now!

Misc. Sony thoughts

Photokina is nearly here and what this? Finally! A hint, a sniff, a wiff of something juicy coming from Sony!

An A750 to be announced at Photokina! An A950 coming too? Possibly with 32mp and four processing Bionz processing engines? Well, that would just float my boat! Also rumored, an A820 which is essentially a rebadged A900? Hmmmmmm, this would be a very good lineup, if all of these cameras hit their marks.

My guess at prices:
A750 $1,199 USD 16.2 APS-C frame, dual-Bionz (translucent mirror and high frame rate of 8-9 FPS?)
A820 $1,699 USD full-frame, 24.6mp dual-Bionz (translucent mirror and 5 FPS again?)
A950 $2,250-2,500 USD 32 megapixels?!?! (translucent mirror, 5 FPS frame rate?)

What would wedding photographers pay for a high-res photo tool which doesn't go KER-THUNK when a photo's been snapped? I know noise was a criticism rightly leveled at the first generation of Alpha full-frame bodies so perhaps this is an example of Sony thinking "outside the box"?

Whatever the case, I'm getting excited for news from Photokina now. Just a month away! Sony, don't let me down!

Of the bunch I'm the least confident in my guess about the A950's price. I can only see Sony as being very aggressive at this point, due to the economy and market forces. If, like Thom Hogan suggests, they're killing off the 24mp FF sensor, and have some to use up, then the A820 could be the last that we see of that one. On the other hand I do think it's likely that they could introduce a significantly faster A950 using this same sensor, but with more processing power behind it, to take the old A900 chassis and launch it into the frame rate of the D3/D3X bodies.

But what about the translucent mirrors they're using on the A560 and A580 bodies. Hmmmmmmm. Those are quite interesting. Canon used to do that a long time ago with their "N"-denoted film bodies (as a high speed, sports-ready camera). I might be VERY interested in an A750 with 16.2mp (though only APS-C sized) and a really high frame rate with continuous auto focusing. That's something they have an issue with in the A700/A850/A900 bodies as I've pointed out before. For all sorts of "normal" photography, they're fine. For motorsports, not so fine.

From the mechanical standpoint, it would be FAR less expensive to go to a translucent mirror on the FF bodies. Quieter, cheaper to produce, and possibly the first with "electronic shutter" rather than an actual blade shutter. The shutter might not get the axe with this series of cameras, but certainly this shows that Sony is thinking about doing away with the shutter altogether.

Monday, August 16, 2010

Recent Learnings

First, my Sigma 70-200mm f2.8 doesn't focus right up close. It close-focuses. When I adjust the D300's focusing system to work up close, then it far-focuses on far subjects. The problem is in the lens, not the body.

Second, I learned from Thom Hogan (Nikon shooter par excellence and camera gear writer) that the D3/D700 uses Nikon's first in-house developed sensor. I thought it was a Sony sensor. Nikon is rumored to be doing a new sensor for an upcoming "D4" body, and won't use the 24mp Sony sensor from the D3X, so Sony's rumored to be considering dropping full frame camera bodies completely. The A900 is out of production, and the A850, while still available, is not currently in production either. No idea what Sony's going to do for a replacement. Thom has some very good guesses on his website so look him up if you want to know more.

This news makes my upcoming camera purchase decision just that much more difficult. Will there be any A900/A850 bodies I can buy? Will there be a better "D700" coming out this fall? Will the new Sony A700 replacement be of sufficient quality and construction to tempt me to an APS-C sensor of 15.2mp?

Decisions, decisions, decisions...

Friday, August 6, 2010

Still no new Sony A7XX?

Hmmmmm, I've read on a couple sites now that Sony might have something like an A950 coming down the pipe this fall, with a 32MP EXMOR sensor. I wonder if that will be the new "back-lit" design that the Sony technology newletter was talking about?

Sony, if you happen to ever read this blog (unlikely) I'd sure appreciate an A900 body with the sensor from the Nikon D3/D700 cameras. That's it. That's all I need. If you're feeling the urge to be competitive, you could stretch it to 14 or 15MP on a full-frame sensor, but don't do that if you're going to dramatically increase image noise.

Thatisall. You are dismissed! LOL!