strange focusing observation

[astroNikon]

So this past weekend I shot my kids soccer game using my d7000 and 80-200/2.8

I tried AFC-Single and AFS-Single
I seem to get more shots in focus using AFS-Single

AND, from looking at pics I seem to get a MUCH higher rate of in-focus shots using my d600
I'm talking like >75% for the d600 versus maybe 25% for the d7000

It's kinda maddening.
I'm going to stick with my d600 and the 80-200/2.8 lens

Also .. and this is weird. When I was taking self-portraits I swear that the "focus point" is not straight in the middle of the lens. I feel as if the real focus point is actually a little above the middle point of the lens.

With the focus points is there just one Single focus point or a set of focus points.
how does the cross type focus points work ?

I'm just trying to improve my focus skills but I feel I need to understand how the focus on the camera works in order to improve.

Any help would be greatly appreciated.

 

[astroNikon]

I've found this to read ==> Understanding Camera Autofocus

 

[coastalconn]

You should try AF-C 9 point and change a1 in your custom menu setting(the pencil) to Focus priority. That should help.. just my humble opinion...

 

[KmH]

The focus point indicators in the viewfinder show the area where the very much smaller actual focus point can be and are not likely in the center of the area.
Those viewfinder indicators are projected onto the focusing screen at the top front of the mirror box.
The actual focus points themselves are in the AF module that is in the bottom of the camera.

The main mirror in the camera has a section that is 50% transparent.
That lets light tough the main mirror to a smaller secondary mirror behind the main mirror.
That secondary mirror directs light down to the AF module in the bottom of the camera.
Optics in front of the AF module then makes 2 identical images and compares the phase of each.
Any phase difference between the 2 images tells the camera which way the lens focus ring needs to be turned to attain focus.
When the AF module has determined both images are in phase it declares the image focused and turns on the in-focus indicator in the viewfinder.

Because only a portion of the light from the lens gets to the AF module is why AF needs help (a light source) if the scene is dark.

 

[WayneF]

The main mirror in the camera has a section that is 50% transparent.
That lets light tough the main mirror to a smaller secondary mirror behind the main mirror.
That secondary mirror directs light down to the AF module in the bottom of the camera.

You are not discussing Nikon SLR. I think you are talking Sony.

Nikon film SLR did use a sensor in the bottom of the camera, metering light literally reflected from the film surface when the mirror was up and shutter was open. Film TTL simply quenched the flash(es) off when metering was sufficient.

Nikon DTTL (first early models) still did this bottom sensor, but from a gray painted spot on the front the closed shutter. Mirror had to be up.

Nikon digital SLR (today) do the metering in the viewfinder, above the mirror..

The mirror is not at all transparent in any Nikon SLR.

 

[WayneF]

So this past weekend I shot my kids soccer game using my d7000 and 80-200/2.8

I tried AFC-Single and AFS-Single
I seem to get more shots in focus using AFS-Single

AND, from looking at pics I seem to get a MUCH higher rate of in-focus shots using my d600
I'm talking like >75% for the d600 versus maybe 25% for the d7000

Be sure to see D7000 menu A1 about focus priority. Otherwise, AF-C can allow the shutter before focus actually occurs. (menu A1 on D600 too). Focus priority is not the AF-C default on either body. Focus is the default for AF-S (menu A2).

AF-S is good stuff when you want focus to occur first, where you place it, like portraits.

And AF-C allows it to keep continually changing focus after half press. Which might be OK if taking a burst, maybe the 2nd or 3rd shot might finally find focus. But IMO, it would be dumb for a single shot not to be in focus.

 

[astroNikon]

The lens I'm using is *not* an AFS (built in focus motor) lens, so I've kinda found/think that with screw focus 80-200/2.8 AF-D lenses that the half-release works best for obtaining focus.

I'm basically back to my old method of half-release in AF-Single mode to obtain the best results. I was curious trying ti all over again.

 

[WayneF]

Does your term AF-Single mean AF-S focus mode? Or does your use mean NOT multiple continuous burst shutter releases?

And AF-S focus motor is something very different than AF-S focus mode. Entirely different things.

Mode Description
AF-A
Auto-servo AF: Camera automatically selects single-servo auto focus if subject is stationary,
continuous-servo auto focus if subject is moving.

AF-S
Single-servo AF: For stationary subjects. Focus locks when shutter-release button is pressed
halfway. At default settings, shutter can only be released when in-focus indicator is
displayed (focus priority; 0221).

AF-C
Continuous-servo AF: For moving subjects. Camera focuses continuously while shutter release
button is pressed halfway; if subject moves, camera will engage predictive focus
tracking (0100) to predict final distance to subject and adjust focus as necessary. At
default settings, shutter can be released whether or not subject is in focus (release
priority; 0221).


My pont is, do see menu A1 and A2, and understand them, and know what you have.

Focus mode can be either AF-S or AF-C, your setting choice.

The difference in AF-S and AF-C focus modes is not about any focus motor, but is about

1. Does it continue trying to refocus after first focus is found? (while you hold half press).

2. Options are: Is first achieving focus mandatory before the shutter will release?

The Default for AF-C is it does Not wait to find focus before tripping shutter.
If you know to hold half press awhile first, it can find focus then, and it works better.
(and both AF-C and AF-S modes have menus A1 & A2)

So if AF-C focus mode, hold half press awhile before final action. Or change to Focus Priority.

 

[Derrel]

My experience with single-point AF for action sports changed one day when I was assigned to shoot a Wilson High track meet about ten years ago. They wore dark,dark green uniforms with very plain designs...basically just a dark green jersey, with the school's name only on the back. I had my 300/4 AF-S and my 70-200 2/8 VR-G. And OMG--what a freaking NIGHTMARE!!!!!!!! THe single AF point could NOT reliably get focus on the athletes. I had to go to manual focus,and the hit rate was not acceptable. I vowed than and there to learn how to use my camera's AF system. Prior to that, I had used single-point, center AF pretty much exclusively.

One tip on the newer Nikon AF system: if you MANUALLY select the AF point to start, the camera can use multiple AF points and can follow that subject as it moves throughout different places in the frame. When using a grouped AF point system, like AF-C, with 9-point focusing, the camera will look toward the central AF spot that is active, but it can also "search" around that spot, to help gather more data if needed,and I think that's the crux of the issue sometimes on smooth-toned, bland sports uniforms. My experience has been that simple, smooth-tone uniforms without designs or numbers are MUCH more-difficult for any single-point AF to get a focus lock on, and are easier to get focus on when there are MORE THAN ONE focus point enabled. I would definitely consider a 9-point or even 21-point AF setup as maybe a viable option. AF-C focusing, and the focus priority can be set to Focus, but I usually set it to Release priority, since at longer distances if the lens is stopped down a bit to say f/5.6, you MIGHT be OOF at f/2.8 but IN-focus when the lens hits the taking aperture, and at longer ranges, focus is less critical. I do not like FOCUS-priority!!! I wanna be able to shoot when I hit the release, no matter what the camera thinks!

If this issue is with your son's soccer team, take note: their jerseys are just as simple as the Wilson track jerseys were, and almost the same, dark green color. Cross-type sensors can see both horizontal and vertically-oriented details/contrasts. The thing with plain, dark uniforms is that the material basically shows very little contrast. The difference between Wilson's PLAIN-front dark green jerseys and the rest of the league's jerseys with a big school name right across the chest was like night and day. Same with football, with the numbers front, back,shoulder, and helmets acting like fabulous focusing targets with contrast in horizontal and vertical orientations.

 

[TheLost]

The lens I'm using is *not* an AFS (built in focus motor) lens, so I've kinda found/think that with screw focus 80-200/2.8 AF-D lenses that the half-release works best for obtaining focus.

I'm basically back to my old method of half-release in AF-Single mode to obtain the best results. I was curious trying ti all over again.

Using an AF-D lens should have no bearing on how you setup your camera... An AF-D lens will be a bit slower to focus, but you can still get good shots.

Focus Mode: AF-C
AF-Area Mode: 9-point Dynamic (D 9)

I would also recommend you try Back Button Focusing (AF-ON). This switches focus from the 'half-press-shutter' to the AE-L/AF-L button on the back of the camera.

When shooting sports you hold down the AE-L\AF-L button while following the action. This lets you pre-focus and keep the action in focus during the 'play' (AF-C keeps the lens focused while things are moving.. This will also help the slower AF-D lens). Then you just push the shutter to take the picture.

Pre-Focusing is the key on an AF-D lens.

Using AF-S would be a nightmare (IMHO )

 

[astroNikon]

If this issue is with your son's soccer team, take note: their jerseys are just as simple as the Wilson track jerseys were, and almost the same, dark green color. Cross-type sensors can see both horizontal and vertically-oriented details/contrasts. The thing with plain, dark uniforms is that the material basically shows very little contrast. The difference between Wilson's PLAIN-front dark green jerseys and the rest of the league's jerseys with a big school name right across the chest was like night and day. Same with football, with the numbers front, back,shoulder, and helmets acting like fabulous focusing targets with contrast in horizontal and vertical orientations.

Interesting
Yes, as you saw, dark green flat jerseys with a small "soccer" emblem up front in upper left.
I had alot of shots that were focused on an opposing player either behind etc who, had dull dark red jerseys with the soccer league in a larger emblem right across the front - even though I know my focus point was on our player. Or someone in the background with much more contrast. basically very minor left to right of the perceived focus point. And I know where I was focusing, and it wasn't on the opposing players.

I'm curious too if the d600 AF works better than the d7000s. I'm kinda sensing that in a general, non-scientific way without enough emperical evidence as of yet.

This has also been the jersey for the last couple years, though 2 seasons ago they had white side panels which increased the contrast immensely. last season with the same jerseys I didn't have this number of OOF shots, but I was using my d600 exclusively with the same 80-200 lens.

 

[astroNikon]

The lens I'm using is *not* an AFS (built in focus motor) lens, so I've kinda found/think that with screw focus 80-200/2.8 AF-D lenses that the half-release works best for obtaining focus.

I'm basically back to my old method of half-release in AF-Single mode to obtain the best results. I was curious trying ti all over again.

Using an AF-D lens should have no bearing on how you setup your camera... An AF-D lens will be a bit slower to focus, but you can still get good shots.

Focus Mode: AF-C
AF-Area Mode: 9-point Dynamic (D 9)

I would also recommend you try Back Button Focusing (AF-ON). This switches focus from the 'half-press-shutter' to the AE-L/AF-L button on the back of the camera.

When shooting sports you hold down the AE-L\AF-L button while following the action. This lets you pre-focus and keep the action in focus during the 'play' (AF-C keeps the lens focused while things are moving.. This will also help the slower AF-D lens). Then you just push the shutter to take the picture.

Pre-Focusing is the key on an AF-D lens.

Using AF-S would be a nightmare (IMHO )

In the past I've found my best solution is AFS-Single focus point.
I use half releases to maintain quick focus as the action is moving.
I use the back button for Focus Lock to get shots of the ball bouncing around towards the goal, etc.
using that method I'm basically a high percentage of Infocus shots. Of the shots that were out of focus, I know The focus point was wrong when I took it.
Also I used Focus Release on both a1 & a2.

I'm going to reread this thread a couple more times.
the main issue, was my d7000 seems nowhere as good as the d600. I have them both set up the same too.
of course, I just jumped back to the 80-200 after trying to use the 70-300/4.5-5.6 lens
I have much more shots In Focus compared to that lens, but that was another thread.

 

[KmH]

The main mirror in the camera has a section that is 50% transparent.
That lets light tough the main mirror to a smaller secondary mirror behind the main mirror.
That secondary mirror directs light down to the AF module in the bottom of the camera.

You are not discussing Nikon SLR. I think you are talking Sony.
. . . . . . . . . . .
The mirror is not at all transparent in any Nikon SLR.

Yes I was discussing Nikon DSLR AF.
Here is a photo of Nikon's MultiCAM 3500 AF module for the D800/D800E and several other Nikon DSLRs. Nikon | Imaging Products | Still image shooting functions - Nikon D800/D800E

If you carefully lift the main mirror in a Nikon DSLR you can see the secondary mirror that hangs behind the 50% transparent part of the main mirror that deflects light from the lens down to the AF module in the bottom of the camera.
If you lock or hold the main mirror all the way up and look in the back bottom of the mirror box you can see where light from the secondary mirror goes down into the AF module in the bottom of the camera.

Or you can go frame by frame through this Nikon D3 shutter release sequence and see the secondary mirror from about 7.5 milliseconds to 20 milliseconds, and again as the mirror comes down after the shutter closes - http://regex.info/blog/2008-09-04/925

 

[astroNikon]

The main mirror in the camera has a section that is 50% transparent.
That lets light tough the main mirror to a smaller secondary mirror behind the main mirror.
That secondary mirror directs light down to the AF module in the bottom of the camera.

You are not discussing Nikon SLR. I think you are talking Sony.
. . . . . . . . . . .
The mirror is not at all transparent in any Nikon SLR.

Yes I was discussing Nikon DSLR AF.
Here is a photo of Nikon's MultiCAM 3500 AF module for the D800/D800E and several other Nikon DSLRs. Nikon | Imaging Products | Still image shooting functions - Nikon D800/D800E

If you carefully lift the main mirror in a Nikon DSLR you can see the secondary mirror that hangs behind the 50% transparent part of the main mirror that deflects light from the lens down to the AF module in the bottom of the camera.
If you lock or hold the main mirror all the way up and look in the back bottom of the mirror box you can see where light from the secondary mirror goes down into the AF module in the bottom of the camera.

Or you can go frame by frame through this Nikon D3 shutter release sequence and see the secondary mirror from about 7.5 milliseconds to 20 milliseconds, and again as the mirror comes down after the shutter closes - http://regex.info/blog/2008-09-04/925

That second link is just plain cool to play with.

 

[astroNikon]

Does your term AF-Single mean AF-S focus mode? Or does your use mean NOT multiple continuous burst shutter releases?

And AF-S focus motor is something very different than AF-S focus mode. Entirely different things.

Mode Description
AF-A
Auto-servo AF: Camera automatically selects single-servo auto focus if subject is stationary,
continuous-servo auto focus if subject is moving.

AF-S
Single-servo AF: For stationary subjects. Focus locks when shutter-release button is pressed
halfway. At default settings, shutter can only be released when in-focus indicator is
displayed (focus priority; 0221).

AF-C
Continuous-servo AF: For moving subjects. Camera focuses continuously while shutter release
button is pressed halfway; if subject moves, camera will engage predictive focus
tracking (0100) to predict final distance to subject and adjust focus as necessary. At
default settings, shutter can be released whether or not subject is in focus (release
priority; 0221).


My pont is, do see menu A1 and A2, and understand them, and know what you have.

Focus mode can be either AF-S or AF-C, your setting choice.

The difference in AF-S and AF-C focus modes is not about any focus motor, but is about

1. Does it continue trying to refocus after first focus is found? (while you hold half press).

2. Options are: Is first achieving focus mandatory before the shutter will release?

The Default for AF-C is it does Not wait to find focus before tripping shutter.
If you know to hold half press awhile first, it can find focus then, and it works better.
(and both AF-C and AF-S modes have menus A1 & A2)

So if AF-C focus mode, hold half press awhile before final action. Or change to Focus Priority.

I have purposely set my a1 and a2 settings to Release Priority.

I have in the past ,with great success use my finger to do half releases to follow action and keep the focus throw as small as possible to prevent the lens from going into a big hunt and lose focus. Then when I want the shot I'll do a full release and possibly use my back button to Lock Focus depending upon the action.

When I use AF-C continuous with half releases I was listening to it to see that it was focusing. But I have found in an extreme example when you use video that there's a large disparity between AFS and AFD lenses. AFS lenses just seem to work better with Continuous focus mode. I don't have a wide range of lenses to test and only have the kit 18-108 DX lens but that blew away for continuous focus my AFD lenses in a video test.

So I tend to shy away from AF-Continuous mode based on those AFS/AFD lense type testing.

But I'm going to go in my backyard and catch a few soccer games this week and test things out again. It's been awhile since I did all the testing. But I'll probably just jump back on the d600 with the 80-200 anyways.