What am I doing wrong? - Karts

M38A1

I was able to shoot Karts for the first time today and it was quite fun and most certainly a challenge. Other than not being very good at panning which I learned today, I can't for the life of me figure out what's going on with a large number of shots. I think I had the whole day on "Continuous" focus and not single servo. ie: it was keeping up with the movement once locked in. I also had VR turned "OFF". These shots were all in the same approach/turn. #1 maybe 45mph, #2 and #3 maybe 35-40mph.

Here's three that make me scratch my head.

#1
From the on-line DOF Calculator, I should be waaayyyyyy safe. Yet the front of the car is perfectly in focus, but from the bumper back, it's out of focus. (or is it motion blur?)

1/160th, panning and f/13 at 200mm

Subject distance 40 ft
Depth of field
Near limit 35.7 ft
Far limit 45.5 ft
Total 9.82 ft
In front of subject 4.32 ft (44%)
Behind subject 5.51 ft (56%)

What's going on here? That front bumper is tack-sharp and the rest of it, back some 5.5' should be as well.

This is straight out of the camera with nothing but a conversion using Irfanview from RAW to .jpg.




#2
Here's one at the apex so it's all left to right motion, again panning. Look at the top of the helmet. It's sharp. But moving down towards the vertically to track from his helmet, everything goes to fuzzy. It doesn't make sense unless the cart is in a motion other than straight/perpendicular from my panning. But even then, the DOF should have covered it with these settings.

1/200th
f/14
112mm
LOW ISO at 100



#3
So here's another one, maybe 10 frames later. The bottom of the kart is perfect, but the rest isn't. Look how the front wheels are canted in relationship to the line of travel. It still doesn't make sense why the two are not either in or out of focus together...




Thoughts?

Could it be that these karts 'dance' so much, ie: bounce side to side soooo fast?
Is it a panning issue from my side?
Is it a focus issue from the camera?

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AceCo55

I get the same thing with dirtkarts. The dirt track is much bumpier and the karts slide through all corners. If the kart is sliding, the back of it will be travelling at a different speed to the front which will lead to motion blur when the shutter speed is low (as in panning).
As the kart passes across me during a pan, different parts of the kart and driver will be travelling in different directions. The tack sharp parts were travelling at the speed of your pan horizontally. Parts that were at this speed may still be oof if they are also travelling up or down.
Maybe that's the reason ... maybe I have convinced myself that is a logical reason ... maybe I'm working in a parallel universe!!

M38A1

Ace-
That's sort of where we're thinking the issues are with these. They are like little mosquitoes bouncing really fast in all directions. For grins, I shot some at 1000th/sec and up I need to go look at next. The pan-blur probably won't be there, but at those shutter speeds, there shouldn't be any I think. But that kills the intent of showing motion in the image.

Thx-

mercphoto

You're over-thinking this with the depth of field calculations. f/13, f/14, it safe to assume you have tons of depth of field. Even enough that much if not all of the background will still be in focus (it won't look that way, due to panning, but if you weren't panning...). This all has to do with relative motion.

In the first shot the kart is turning. The front of the kart and the rear of the kart are travelling in different relative directions with respect to the camera. You simply cannot get the entire kart focused in a shot like this. Physics will not allow that to happen. IT DOES NOT MATTER. Get what is important sharp: driver first, front of kart second.

Second shot, that side pod is not focused simply because it is almost certainly bouncing up and down. That part of the kart is not rigidly fixed, it can move some, bounce some. Again its that relative motion thing, the side pod is not precisely following the motion of the rest of the kart.

Third shot, I don't understand what you are trying to say with respect to the front tires.

Panning and karts takes a lot of practice. Cars are easier because cars are so rigid. Not so with karts. Bumpers that bounce, side pods that bounce, driver jostling in his seat and moving arms and legs, exhaust pipes that vibrate, etc.

M38A1

Bill,
Thank you for your input. Secretly I was sort of waiting for it.....

I totally understand what is going on with these now. I really didn't know they bounced as much as they did, and that in itself makes them difficult. And I understand the DOF/panning much better with your explanation.

On #3 and the wheels, I was just trying to guess that the Kart was not moving in a straight line, ie:, front pointed one way and the rear another thus lending support for the differing direction thing.

Wow. What a learning experience this has been.

Thanks.

mercphoto

M38A1 wrote: »

I totally understand what is going on with these now. I really didn't know they bounced as much as they did, and that in itself makes them difficult. And I understand the DOF/panning much better with your explanation.

I still have an occasional rib injury from my karting days that reminds me how much they can bounce around.

Back to panning and depth of field, think about what this truly means. If your camera was stationary with that type of aperture you'd have a sharp background. But because you are moving the camera that background isn't sharp anymore, it is blurred due to the motion of the camera. Further, your camera motion is in one specific direction, in a straight line. If you were to pan next to a fence, for example, maybe the type of Armco you might find at a race track, you'd see something interesting as an artifact of this combination of long shutter, panning, and high depth of field. You'd find that the horizontal edges of your fence are rather sharp, but the vertical edges are blurred. This is the striking difference between large aperture "bokeh" blur, which is the same in all directions, and panning blur, which is blurred in one direction and sharp in the other direction.

When you pan a car, kart or bike, follow the driver, not the front of the vehicle. You probably already know why I'm pointing that out.

M38A1

mercphoto wrote: »

When you pan a car, kart or bike, follow the driver, not the front of the vehicle. You probably already know why I'm pointing that out.

Thanks again for the tips and insight. Absolutely makes perfect sense to me.

As for following the driver.... heck. I had a hard enough time just keeping my focus point on ANY part of the target (driver, kart, bumpers etc) lol.... Man they scoot rather smartly.

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Gary752

Another tip is to continue panning with your subject after you click the shutter. Also, do your panning shots on a straight away, and try and get some close to their level.

GaryB

Zerodog

Ok this might be a dumb question, but why did you have VR off? I thought this helped with panning shots.

Aside from that I like the theory of carts bouncing a lot. One solution might be flash. Even in broad daylight. Use rear curtain sync. You still can get the panning motion and have more chance of freezing all of the cart.

mercphoto

Don't about VR, but Canon's IS systems can either help or hinder panning. If you only have normal IS then it hurts you, as the lens will try to stabilize ALL motion, including the panning motion. If your Canon has multiple IS modes then you can use IS Mode 2, which specifically only dampens lens motion perpindicular to the motion of travel of the lens. But even then, every professional motorsports photographer I know pans without image stabilization. It can impact how quickly focus is locked, and it does take a moment for the IS to stabilize and reach an equilibrium.

Once you get used to panning and get the technique down you won't find any benefit to VR/IS.

Flash isn't a bad thing in general for any of those kart racing shots, whether panning or not. When I was shooting karts and MX I used flash nearly all the time. Helps a bit with shadows, gets a bit of reflection off the shiny stuff, and can add a bit of pop to the vehicle as well.

M38A1

Re: VR "OFF", I read it in the interwebz as how to shoot karts, so it must be true....

Seriously, I did read a few shooters turned it off so that's what I did.


Re: flash, I did bring an SB900 and thought about setting it up to do shadow fill when I realized I was on the wrong side of the track from the sun. But I didn't want to distract the drivers (or at least thought I'd distract them) so I didn't set it up.

This is all a GREAT discussion on shooting these little targets..... Learning a lot here.

Thx.
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M38A1

Just looking at the 2nd and 3rd shot above, they are in almost identical spots on the track. I'm guessing there was a little bump just before them, as you'll note both shots have their wheels canted to the right with the tail end trying to swing out. I'm guessing all my shots there have this problem too.... Will have to go back and look next. Also, I'd guess since #2 and #3 are in the same spot with the same class of cars (ie: speed/lines) that I had the focus point on the helmet of one and on the side of the car at the number plate on the other. That would explain a lot based on your input.

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