Aperture Priority

[neiloliver]

Jimmy, Stu, et al..

I must admit I am struggling getting fast moving things (RC cars) in focus in Av mode. I am currently only using the 17-85mm F4-5.6 IS USM with the 450D as the 70-300F4L is not here yet. I am trying to pan correctly and have taken many shots, but end up going back to Shutter priority..

If the damn things stand still then i am fine... :lol:

I have only tried photos over two meetings and of course I need a lot more practice but want help on which direction to try. Ideas please?

N

[JCJC]

Your other shots looked good, on our 400d we up the iso to 800, this will give you faster shutter speeds, Stu suggested we set the camera for "cloudy" - makes everything a bit more colourful. I try to keep to F8 and not drop down to F4 or 5.5, keeps more in focus.

Strikes me there are 2 methods - sit near a corner or any point round the track, focus on a point on the track (possibly centre weighted focus) try to press the shutter when you think a car is in the frame, you can crop lots after.

2nd method, and this is how we mostly set the canon (thanks again Stu), is with servo focus, find it in the menu somewhere, holding the shutter button half down and following a car round the track in the viewfinder, the autofocus will hold the car in focus (feels weird), snap away......we fill the card up, 400+ shots and end up with a few we like, but are still "just getting there"

both these methods are designed to save fractions of a second, the time it takes for the camera to focus, when the shutter is pressed that calculation and adjustment is already made, have fun. Unfortunitly Jordan at 15and a bit is keener eyed and faster fingered than I ever was/am.

[josh_smaxx]

You can put it in manual focus, focus it on the apex of the corner and then back it off slightly if your using wide apetures, or just leave it focused on the apex if your looking at F8+ type apetures. Auto-focus is a difficult on and i only find it to work if your following a car around panning with it, if not then it tends to focus on the background more often than not as it doesnt pick the car up for the tiny amount of time its in the frame.

[telboy]

I had the same problem with AV at the last meeting I took photo's at.

Couldn't get anything sharp. I tried the higher iso's and it just came out over exposed and way too light. the conditions weren't too bad, overcast but light.
Couldn't get anything coming towards or going away from me.

Maybe its a Canon thing.:p

[josh_smaxx]

I had the same problem with AV at the last meeting I took photo's at.

Couldn't get anything sharp. I tried the higher iso's and it just came out over exposed and way too light. the conditions weren't too bad, overcast but light.
Couldn't get anything coming towards or going away from me.

Maybe its a Canon thing.:p

Or maybe its just something thats happening now ??? because i had the same problem at york, and i took some immensly sharp pictures at shields. im using a fuji BTW.

[mole2k]

I find this quite a hard question to answer as I cant really say i've ever had this problem myself. I've just always shot Av from I started getting into photography as I seen the Aperture as a much more important part to control in the camera than the shutter speed as really the shutter speed can be any range of values and still be 'correct'.

Could it be that when shooting in Tv mode the camera is selecting a lot higher aperture values than you currently are using giving you a narrower depth of field. So the shots you are taking are still out of the focus plane but within the acceptable sharpness range due to the higher aperture.

With Av and the aperture set wide open you would have to be a lot more accurate with the focus as the acceptable depth of field is a narrower than it otherwise would be.

Got any shots with intact EXIF to show Tv mode working for you and Av mode not working ?

[neiloliver]

Thanks for all this advice. I dont have any 'bad' shots left which I can post as I deleted them. :(

I will see how I get on at the next meeting and report back.

Thanks again

N

[Stu]

Is it a focusing problem rather than a shutter speed problem?

The basic rules I use for RC are,

When the car is moving toward/away from you at speed you need to pre-focus on the spot where you want to take the image, camera should be in 'one-shot' AF mode. I often focus on the spot then flick the lense into manual to lock the focus. The following is pre-focused on the painted track marker.....

http://www.northernracer.com/images/oswestry08/2wd/21.jpg


When the car is moving but keeping a constant distance from you it's a panning shot, sounds like this is what you are trying to do, it's not easy. I use the 'Servo' AF mode (not sure why its called this, I assume it's 'cos the lense has a servo motor in it :eh?:) As long as you can keep the red-dot of the AF point on the car it should be good.

When you talk about Tv vs Av it matters little what you use as long as it's set right fot the light conditions, I use Tv mostly unless light is poor, Jimmy (I think) uses Av a lot more.

It's always difficult if light is moderate or poor. Aperture wide means a tough time focusing, as Mole points out. Aperture too tight and you'll get movement blurr as the shutter speed slows down. You always have to balance the two.

[OldTimer]

A handy hint is to make sure you only have the center focus point selected, then the cameras focusing is just working on that one point rather than trying to calculate for 5 or 8 points etc.

I have always used Tv when i did the motorsport stuff, and if i cannot get the shutter speed i need i just up the Iso, these days noise at the higher iso settings is less of a problem.

Also try picking a slow corner on the track as it will be easier to track the car and get it in focus.

The attached was shot from memory at i think ISO 800 just before a big downpour, with little noise in the photo.