Where am I going wrong?

[Spesh]

Hi guys. I have been at the lake this evening, shooting some more waterskiing. However, I seem to be struggling with softness/lack of focus in my captures.

I am shooting from the bank of the lake with a D300 and Sigma 120-400mm telephoto. The light was starting to fade slightly as it was evening time, so I had the ISO set to 1250. Shutter speed was 1/2000 and f5.6 on full manual mode.

I have the AF set to release + focus, 21 point AF area and focus tracking with lock on set to short. The maximum focul length I used was around 320mm. For some reason, I just can't get the images to look crisp. I wasn't sure if this was due to incorrect settings for the conditions, or just lack of light. Anyway, here are some samples to show the problem I am having....












Shots from the boat with the same setup appear to come out perfectly sharp......

 

[amolitor]

My guess is you're using a longer focal length for the on-shore photos?

It looks to me like your lens is a bit softer all around for those, although the focus ALSO appears to be missed as well (my old eyes could be fooling me, since I sort of think the focus in all is on his shorts, which are higher contrast so I am probably just seeing acutance anyways..)

 

[480sparky39 38]

The first three looks like you just missed focus. However, it looks like the focus point isn't preserved in the metada, so it's hard to tell where the camera focused.

It could also just be the lens is soft at the longer focal lengths.

 

[Derrel]

I would try switching lock on duration to LONG. You want the AF module to pick up focus then hold onto the focus a bit on the "long" side, and not suddenly go into "seek" mode everytime the wake behind him changes its shape. START by MANUALLY selecting the desired AF point grouping; the AF system will read the RGB of the desired target that way, and will try to follow that target. If you try and KEEP the skier off to 1/3 of the side of the frame, then use a group AF cluster to cover him, and to de-emphasize the need to hunt thru 21 or 51 AF points.

One thing too: that lens is rather slow, f/stop wise...and I think the 21-point AF is too many AF points. SO, MANUAL AF selection to start each sequence, using a group of 9 points, Lock-On set to SLOW or Medium, not fast, and hold your mouth just slightly ajar while mashing down on shutter button and softly praying for solid lock on...I usually pray, "Please let me hit perfect focus, please let me hit perfect focus," over and over and over.

 

[Spesh]

My guess is you're using a longer focal length for the on-shore photos?

It looks to me like your lens is a bit softer all around for those, although the focus ALSO appears to be missed as well (my old eyes could be fooling me, since I sort of think the focus in all is on his shorts, which are higher contrast so I am probably just seeing acutance anyways..)

Yes you are right, I was using a longer focal length from the bank and this lens does become noticeably softer, beyond 300mm.

I would try switching lock on duration to LONG. You want the AF module to pick up focus then hold onto the focus a bit on the "long" side, and not suddenly go into "seek" mode everytime the wake behind him changes its shape. START by MANUALLY selecting the desired AF point grouping; the AF system will read the RGB of the desired target that way, and will try to follow that target. If you try and KEEP the skier off to 1/3 of the side of the frame, then use a group AF cluster to cover him, and to de-emphasize the need to hunt thru 21 or 51 AF points.

One thing too: that lens is rather slow, f/stop wise...and I think the 21-point AF is too many AF points. SO, MANUAL AF selection to start each sequence, using a group of 9 points, Lock-On set to SLOW or Medium, not fast, and hold your mouth just slightly ajar while mashing down on shutter button and softly praying for solid lock on...I usually pray, "Please let me hit perfect focus, please let me hit perfect focus," over and over and over.

I set the AF to 21 points, because I was concerned that my aim wouldn't be accurate enough for the 9 point area. What you are saying makes sense though, so I will give that a go tomorrow. We have a slalom comp at the weekend and the world record holder will be competing at the club, so I really want to get this right before then...lol.

 

[SCraig]

Personally I would turn that auto-focus tracking off. When it is on you don't know what it decided to focus on in the image, and the choice isn't yours to make. You are at the mercy of the auto-focus module. In the first one clear focus is on the bottom of the ski. In the second and third it's on the wave. In the fourth one it's the very tip of the ski.

Your auto-tracking is deciding what you want to focus on, not you.