Old 03-16-2010, 04:08 AM   #1
Smoke
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I was out shooting today and I think my AF focused on the wrong thing. Because of this my photo are not sharp. For future reference how should I avoid my AF focusing on the wrong thing, or should I just choose where I want the camera to focus?

Here is a link to the rejection:
http://www.railpictures.net/viewreje...&key=546619464

Thanks!
-Andrew
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Old 03-16-2010, 04:27 AM   #2
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To me it looks like a photo that was out of focus and then oversharpened. Personally, I never had an autofocusing camera till about four years ago when I purchased my first DSLR. I always used manual focusing, usually either focusing on the number boards to keep them crisp, or a particular spot on the ballast and clicked when the train reached that spot if I saw the train coming at speed. Usually, it was pretty easy to follow and I got used to it. I still have a problem trusting autofocus and tend to shoot manual where I feel more comfortable. It's something I'm just used to.

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Old 03-16-2010, 04:42 AM   #3
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I can't shoot on Manual and expect to get much usable. You should choose the AF focuses and see if your images look sharper.
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Old 03-16-2010, 05:08 AM   #4
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Quote:
Originally Posted by Smoke View Post
I was out shooting today and I think my AF focused on the wrong thing. Because of this my photo are not sharp. For future reference how should I avoid my AF focusing on the wrong thing, or should I just choose where I want the camera to focus?
You need to say a bit more on what you do. You have a Canon XS. Are you selecting the center focus point, are you using the all points focus, what? Sorry, the Canon terms for this stuff are not coming to mind.

One way to go about things is to set the camera for only center-point autofocusing, prefocus on a point of interest, and then recompose, if that point is to be off-center. Another way is to choose the focusing point manually for each shot and then autofocus as usual.

But I'm not convinced we know everything we need to know. You shot at f/8 and 1/500 sec. That should provide plenty of depth of field to address any focus issue (unless for some reason you focused on the closest section of fence, in the right corner) and avoiding blur while handheld.

What does the original look like? The copy here seems to be well processed. Like Chris said, oversharpened, despite what the rejection reason says.

Another possibility is the screener clicked on the wrong option.
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Old 03-16-2010, 05:23 PM   #5
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You need to say a bit more on what you do. You have a Canon XS. Are you selecting the center focus point, are you using the all points focus, what? Sorry, the Canon terms for this stuff are not coming to mind.
I was letting the AF select where to focus. I was pressing the shutter down halfway and letting the camera focus wherever. Up to this point it has always focused on the right subject and so there was no reason to change. Now that is has screwed up a shot though I am going to focus using a different method.

Quote:
Originally Posted by JRMDC View Post
One way to go about things is to set the camera for only center-point autofocusing, prefocus on a point of interest, and then recompose, if that point is to be off-center. Another way is to choose the focusing point manually for each shot and then autofocus as usual.
This is what i am going to start doing. I might miss a couple shots when I first start but that's better than missing a shot down the road due to the AF.

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Originally Posted by JRMDC View Post
But I'm not convinced we know everything we need to know. You shot at f/8 and 1/500 sec. That should provide plenty of depth of field to address any focus issue (unless for some reason you focused on the closest section of fence, in the right corner) and avoiding blur while handheld.

What does the original look like? The copy here seems to be well processed. Like Chris said, oversharpened, despite what the rejection reason says.

Another possibility is the screener clicked on the wrong option.
I thought it looked oversharpened as well, but i'm never sure. I originally thought it would get hit with blurry. I attached the original shot and as you can see I cropped it quite a bit. This wasn't the shot that I originally was planning to upload so it isn't composed the best to begin with. The other shot I was planning on uploading was even blurrier than this one...

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Old 03-16-2010, 05:58 PM   #6
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Hi Andrew,

It would be worth spending some time reviewing the section of your camera's manual that addresses autofocus (AF).

I'm a Nikon user, so I don't know the particulars about Canons, but I also can't imagine that the feature functionality is that much different. Most cameras have a grid of AF points in the viewfinder. The more expensive the camera, the more points they tend to offer. Most cameras also offer one or more means to select which focus point will be used. On my Nikons, there are a couple of automatic options in which the camera can select the spot. One option is to totally let the camera find the subject. Another is to focus on the subject manually and let the camera adjust the focus point if the subject moves. I personally don't use either function. I use full manual selection in which I pick the focusing point and then compose to put the subject on that point. I basically tell the camera to shut up and color!

How you use AF is a personal choice. My suggestion is to fully understand how each mode works and practice with each a little bit. With the knowledge and experience, you can make the best choice for you.

The most important piece of advice I have is to resist the temptation to let the camera make all of the focusing and exposure decisions for you. Technology works best for us when we use it in conjunction with our human skills and decision-making abilities....not as a replacement for them.
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Old 03-16-2010, 06:41 PM   #7
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I attached the original shot and as you can see I cropped it quite a bit.
That is the problem!

a) you did a severe crop, more than the combination of sensor and lens quality could withstand. Too few original pixels left.

b) it may be that, given the severe crop, if you were handholding. you may not have had enough shutter speed to stop blur. Your effective focal length after cropping was pretty long.
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Old 03-16-2010, 06:47 PM   #8
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Looks like heat distortion to me. Cold ground warm sunny day will do that, on top of the cropping of course, which is a killer.

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Old 03-16-2010, 09:47 PM   #9
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Looking at the original, I'd say the AF focused on the "Reduced Speed Ahead" sign. Everything in front or back of that plane of focus is soft to my eye.

In Aperture (and probably Lightroom) you can bring up the AF points in an HUD to see where the lens focused.

In my early days of AF, I'd put the focus on full auto. My reward was a lot of soft engines because the camera focused on the foreground framing element.

So for walking around, I generally leave the AF to focus on my Canon's center dot.

When on a wedgie, I'll usually pick somewhere mid engine. (Of course the most important consideration is that the number boards are sharp)

Other times, I pick the most important part of the frame and then select the appropriate focus point.
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Old 03-17-2010, 01:34 AM   #10
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As AB(2) once said, selective focus! You're using a Canon XS, so it should have seven focal points. With that being said, I'd use one of those seven focal points to make sure your train will be in perfect focus.

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Old 03-17-2010, 03:39 AM   #11
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Thanks for the help guys. Was out today and didn't let the camera focus but told it where to focus. It's easy when your shooting slow moving coal trains.
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