Hello everyone,

This is a follow-up to my post titled "Looking for Advice on Lenses." Thanks to all who replied to that post. Based on your comments I rented a 70-200 F4L for one month to test it out. I have used the lens at several of my son's little league games with mixed results. I suspect that most of my misses are due to pilot error and not the lens - I am still learning how to shoot in manual mode vs. "P". My first concern is how to do a better job focusing. I just signed up for a year of image upload service. Once my membership is activated, I can upload a picture or two to show what I mean by this. In the meantime, I will try to describe the problem.

I am taking shots at F4 and 200mm of the boys making plays in the field using a polarizing filter. In many of my shots, the subject is slightly blurred. I don't think it is a shutter speed issue as I am shooting at 1/250 or faster. Looking at the grass on the field it seems that I am either in focus a little behind or a little in front of the subject.

Does anyone have suggestions on the techniques for obtaining sharp focus in this situation? I have tried two approaches. The fist is manual focus and the second is to use my Canon 20Ds AF with using only the center point.

For those who shoot outdoor sports, what F stop do you typically use? So far I have only shot with the lens wide open at F4 (typically at ISO 200 or 400). I guess I could stop down for a bigger depth of field, but am concerned that my shutter will be too slow. Later today I have another game. I am going to try taking my polarizing filter off and stopping down a bit. Any suggestions would be greatly appreciated as I only have a few more games before I need to return the lens.

On another note, for those who suggested I buy the 85mm F1.8, I can see what you mean. It is an amazing lens! I tried one out in a local camera store and was blown way by the brightness of the image through the lens. All of my indoor shots with it looked great. Unfortunately, they did not have a 70-200 F2.8 for me to try out. I wonder if the brighter zoom would make it easier for me to obtain manual focus? I may need to rent one of those next to see...

Most sports photographers don't use a polarizing filter so why do you? You immediately lose 2 f-stops by doing so.

Get rid of the filter, shoot at 1/500 sec. or faster, even if it means moving your ISO up to 800. Wide open at f4 should be fine for DOF. Center point focusing only with AF. Forget MF for action shots.

Imagemaster wrote:
Most sports photographers don't use a polarizing filter so why do you? You immediately lose 2 f-stops by doing so.

Get rid of the filter, shoot at 1/500 sec. or faster, even if it means moving your ISO up to 800. Wide open at f4 should be fine for DOF. Center point focusing only with AF. Forget MF for action shots.

Hi Imagemaster,

This is exactly the kind of advice I was looking for. I took a class in DSLR photography and the instructor said you should always use a polarizer - even in indoor shots. I will switch the polarizer for a UV lens and put your advice to the test. I will post the results tomorrow (or when my upload account is updated).

Better tell that photo instructor ? - to lay off the hard stuff.
Cheers
Harry

Chip, you need more shutter speed. At 200mm on a 20D the effective/apparent focal length is 320mm. A typical photographer needs 1/320 sec shutter speed to make a stationary subject look reasonably sharp. If the subject is moving then you need double that or more, depending on the speed of movement. 1/200 is way too slow no matter how good or bad the focus is.

Then you have a problem with the actual focus. At f/4 the 20D cannot do high precision focus and so you get standard precision. That's not exactly bad, and if you shot at f/8 or so you wouldn't notice the difference, but shooting at f/4 you may notice.

Then there's the user technique. Are you using AI Servo mode to track the subject ? If not (i.e. if you're using One Shot mode) then you are really up against it. If you are using AI Servo then are you giving it time to lock onto and track the subject before you shoot ? And are you aiming at the subject before you initiate the AF ?

Using a polarising filter is great to reduce reflections off water and vegetation but probably not necessary for sport. If you happen to be using it just for lens protection then don't. If you are comparing an f/1.8 with and f/4 lens then you'll notice the brightness of the f/1.8 but it's not exactly staggering. However, if you compare it with an f/4 lens fitted with a polariser filter (effectively as dark as f/8) then the difference is staggering.

The AF sees the same difference. By puting a polariser on the lens you let less light through to the camera and that will slow down the AF even on a subby day. In poor light it will kill the AF.

The reason for using the centre AF sensor only as suggested by Imagemaster is that the centre sensor is a cross-type that can see contrast edges in two dimensions. The others are linear, and if the edge you are focusing on is roughly parallel with the sensor then the sensor is blind. It can only see clear edges and only if they cross the sensor.

If you had an f/2.8 or brighter lens then the centre sensor works at high precision but f/4 is ok in good light (without the polariser).

The 20D AF is a bit old and certainly not the fastest for tracking moving subjects. If you wanted to do a lot of focusing on moving sports or birds or animals then a better camera would help, probably more so than an f/2.8 lens.

Sports photographers shoot at large apertures (often the maximum available) for two main reasons:
1. It lets them use faster shutter speeds to freeze the action and so get a sharper shot.
2. The relatively narrow depth of field helps blur the background. The background is usually close and cluttered and by blurring it even a little you can help to separate your subject from the background if the subject is sharp enough.

- Alan

ChipinSD wrote:
I will switch the polarizer for a UV lens and put your advice to the test.

Forget about the UV lens also. If you are worried about protecting the lens, use your lens hood, which should be on anyway.

Alan321 wrote:
Chip, you need more shutter speed. At 200mm on a 20D the effective/apparent focal length is 320mm. A typical photographer needs 1/320 sec shutter speed to make a stationary subject look reasonably sharp. If the subject is moving then you need double that or more, depending on the speed of movement. 1/200 is way too slow no matter how good or bad the focus is.

Then you have a problem with the actual focus. At f/4 the 20D cannot do high precision focus and so you get standard precision. That's not exactly bad, and if you shot at f/8 or so you wouldn't notice the difference, but shooting at f/4 you may notice.

Then there's the user technique. Are you using AI Servo mode to track the subject ? If not (i.e. if you're using One Shot mode) then you are really up against it. If you are using AI Servo then are you giving it time to lock onto and track the subject before you shoot ? And are you aiming at the subject before you initiate the AF ?

Using a polarising filter is great to reduce reflections off water and vegetation but probably not necessary for sport. If you happen to be using it just for lens protection then don't. If you are comparing an f/1.8 with and f/4 lens then you'll notice the brightness of the f/1.8 but it's not exactly staggering. However, if you compare it with an f/4 lens fitted with a polariser filter (effectively as dark as f/8) then the difference is staggering.

The AF sees the same difference. By puting a polariser on the lens you let less light through to the camera and that will slow down the AF even on a subby day. In poor light it will kill the AF.

The reason for using the centre AF sensor only as suggested by Imagemaster is that the centre sensor is a cross-type that can see contrast edges in two dimensions. The others are linear, and if the edge you are focusing on is roughly parallel with the sensor then the sensor is blind. It can only see clear edges and only if they cross the sensor.

If you had an f/2.8 or brighter lens then the centre sensor works at high precision but f/4 is ok in good light (without the polariser).

The 20D AF is a bit old and certainly not the fastest for tracking moving subjects. If you wanted to do a lot of focusing on moving sports or birds or animals then a better camera would help, probably more so than an f/2.8 lens.

Sports photographers shoot at large apertures (often the maximum available) for two main reasons:
1. It lets them use faster shutter speeds to freeze the action and so get a sharper shot.
2. The relatively narrow depth of field helps blur the background. The background is usually close and cluttered and by blurring it even a little you can help to separate your subject from the background if the subject is sharp enough.

- Alan

Hi Alan,

Thanks for the great advice. I never considered hand shake at 320mm. I will swap out my polarizer for a UV filter. I am not sure what focus mode I was using. I will check and make sure I am using AI Servo. On the LCD display it shows a rectangle with a few additional lines next to it (if that makes sense). I will check my manual to be sure to be in the right mode. I do aim at the subject and push the shutter button down half way before taking the picture. I will leave the lens at F4 and adjust the ISO to whatever I need to get my shutter speed to faster than 1/640. Also I will rely on AF instead of MF.

Interesting advice on the camera. Is the 30D much better than the 20D? I saw a 40D and loved it, but spending $1,000 to upgrade my camera body would wipe out my lens budget. A used 30D would not be too bad after my trade-in of the 20D. I need to sign off now but will think through your ideas more when I have some time. Right now I need to get my son ready for his game. Thanks again.

The 20D and 30D are pretty much identical aside from spot metering and a bigger LCD screen. You shouldn't have any problems with the action tracking performance, I've tracked monkeys running through trees using a 30D and the same lens you've mentioned.

Chris

ChipinSD wrote:
Alan321 wrote:
Then there's the user technique. Are you using AI Servo mode to track the subject ? If not (i.e. if you're using One Shot mode) then you are really up against it. If you are using AI Servo then are you giving it time to lock onto and track the subject before you shoot ? And are you aiming at the subject before you initiate the AF ?
- Alan

Hi Alan,

I just checked the camera and all I can say is oops! I was set to One Shot - not AI Servo. I have since changed this.

What is everyone's opinion on shooting fully manual vs. fixing the aperature at F4 and letting the camera set the exposure via metering? If you like metering, would you use partial or center weighted given that my subjects are filling maybe 25% of the center of the frame?