580EX high speed sync slows Servo AF?

I shot some basketball today using a few lenses and my 580 EX. When shooting with the 17-55 f/2.8 and bouncing the flash, I had in focus images 71% of the time (22/31). With the 70-200 f/2.8, my images were in focus 64% (16/25) of the time.

I shot with the 85 f/1.8 but used direct flash / in high speed sync mode. Shutter speed was 1/500 or 1/640. The in-focus percentage was 42% (11/26).

This lens is a very fast focusing lens and has always been my best performer in basketball, yielding the greatest percentage of keepers. Today, however, it was the worst of all.

Did HSS impact my system's ability to follow the action in Servo focus mode?

I don't understand why you need HSS when the flash duration is fast enough to stop the action (stops action better than your shutter speed of 1/500 or whatever)...

I can't imagine a connection between the flash setting and focus speed.

What mode were you in? Post some images? It may be camera shake. Doesn't the 17-55 have IS?

What f-stop were you using in the different situations? Your f/2.8 lenses can't go to the f/1.8 (duh!) that the 85mm does. If you were shooting at f/2.2, 2 or 1.8, then there is a higher probability of the players being out of the depth of field and thus more of your shots will be be OOF with the faster lens.

OTOH, you did state your 85mm has been the best for you in the past.

I've experimented with HSS and didn't notice any focussing problems, but I didn't keep track like you did.

We are back to same old issue of not keeping ambient low compared to flash.

Keeping that aside, I do think there could be a relation between slow focus when using flash. Now camera has to talk to flash and also other way around, particularly when you in HSS mode, so that could slow down things. With flash in manual mode, there is no communication except trigger now.

It wasn't a "need", more of an experiment. I was interested in using the flash to just give some gentle fill. SS was dictated by the ambient lighting.

I can imagine one. The camera and lens are a computer system. There is a processor (DSP) inside there that has to process a bunch of stuff in real time. I suspect Servo Focus gives the DSP more to do. HSS may as well. It might be that those two combined, slow the DSP's real-time loop enough that it it can't quite keep up with the action.

This first photo shows that the flash, bounced off the ceiling is NOT fast enough to freeze the action. Compare the face, ball and feet. In this case, I believe the flash is enough above ambient light that the blur isn't from ambient ghosting, but is simple motion blur.

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Here's a shot taken with the 85 and flash in HSS. Notice the focus zone is on the front foot of the defender. The offensive player is clearly out of the focus zone despite the fact the he is the one who I focused on.

In any case, I'm not sure I like the look of the HSS shots so I'll be returning to the bounced flash technique because I prefer the color & overall look of the photos.

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Keith in your first shot, I don't think you have flash 2 stops above ambient. Look at the cheerleaders in the back or the spectators. What is typical lighting in your gym? That will tell you the ambient levels.

Using HSS mode drops the power a lot. You won't see many sports shooters using HSS mode. Same reason sports folks used to like the 1/500 sync speed of the original 1d which amde life easier for someone shooting with flash.

I think both of these shots are lit primarily by ambient light. The shadows just don't fall right. Besides, I don't think anyone could move fast enough to blur a picture when the primary light was a Speedlight unless it was set to high speed sync.

I know you don't like the direct flash look but just take a look at these shots by Dave.

http://www.davehoffman​nphoto.com …ll-with-off-camera-flash/

He is using his flash at 1/8 power. It is hard to over power ambient when using bounce flash.

n1as wrote in post #6962339
There is a processor (DSP) inside there that has to process.

According to Canon, there isn't. When they specify the type of processors, they list them as RISC-architecture devices. The image processor (DiGiC) may be of DSP nature, at least to some extent, but they never tell. Besides, it's not handling normal autofocus, but processes the image when it's taken.
This is what Canon says in their white papers, when they say anything at all. No clue to this mystery there, though.

I usually shoot ISO 3200, 1/500 f/2.5. With flash, I'm shooting ISO 800, 1/250, f/3.5. If my math is right, 1/500 f/2.5 equals 1/250 f/3.5 at the same ISO and my flash setting uses an ISO value 2 stops lower than ambient. So, yes, the flash is 2 stops above ambient.

The shadows fall just like ambient because I'm bouncing flash off the ceiling so the lighting is coming from the same direction as ambient. 580EX is about 1/850 at full power so it's ability to freeze action is not THAT great. Add to that some ghosting from the ambient and, well, you see what you see.

I checked 'em out. Cool photos, but I really don't like the look of direct lighting. It is just too ... fake. I'd go back to shooting ambient at ISO 3200 before I'd use direct flash ... I think

BUT - getting back on topic - I shot another game last night with the 50 and 85. I bounced the flash off the ceiling for the whole game. The 85 once produced in-focus results on 67% of the 18 shots I took with it. I know the sample size is small, but I'm thinking HSS slows down Servo focus.

Your ambient is ISO3200, 1/500, and f2.8 (make it easier compared to f2.5). This is same as ISO1600, 1/250 and f2.8

Now if you shoot at ISO800, 1/250 and f2.8 with flash (your shot posted above), you only 1 stop above ambient, isn't it.

bobbyz wrote in post #6971775
Your ambient is ISO3200, 1/500, and f2.8 (make it easier compared to f2.5). This is same as ISO1600, 1/250 and f2.8

Now if you shoot at ISO800, 1/250 and f2.8 with flash (your shot posted above), you only 1 stop above ambient, isn't it.

Yes, in that case, it is 1 stop (or maybe 1 and 1/3). Last night, I stopped down a bit to f/3.5 so I was more like 1 2/3 stops above ambient.