Question on exposure and focusing

[Nomadicus]

Manual focus is good when there cannot be a defined focal point for the camera to lock on. Once I missed a good shot of a nest of baby gators because the focal lock was always on some grass in the foreground. Working in a hurry I just blew it. Mama gator was under the boat and I'm leaning over the side trying to concentrate on the babies while wondering when ma gator was going to take my camera away from me. Be careful to of switching to the manual mode on the lens and forgetting it's on manual. I've lost some important shots that way too. Happy shooting with that Canon now.

[kdog]

Hey you guys... Canon has what's known as "full time manual focus". It works like this. Press your shutter button half-way down to AF as normal. But then leaving the button pressed half-way, simply rotate the manual focus ring to tweak the focus on your obscured subject. When it looks good, press the rest of the way to get the shot. Do not release the shutter during this process, and the AF will not override your manual tweak.

Also, and this is very important, make sure your diopter is set correctly so that you can trust your manual focus.

[Nomadicus]

Yep about that diopter. Mine is maxed so no adjustment necessary anymore

[RayinAK]

I will add, that the photo above can be slightly fixed with software, but by lightening it with it, the sky is overblown. That's one of the primary reasons why exposure bracketing is used in such cases by photographers.

[RayinAK]

Originally Posted by Brill

Thanks for the replies everyone. I will give these things a try. In the case of the deer picture I described, using only certain focus points should work. What if my subject is behind a fence, is manual focus the way to go there?

Yes, you can focus manually. But remember that most Canon lenses allow you to manually adjust focusing. But be careful, since you can damage the servo (motor) on the lens. I can adjust the focus of my EF 200mm f/2.8L prime as follows: Press the shutter button half-way to focus the lens on the subject, and with the shutter button held down (half-way), I then adjust the lens manually if I need to, and finally press the shutter button all the way. Not all lenses allow you to adjust the focus this way when on auto-focusing. Read the lens instructions first. If in doubt, just move the AF/M switch on the lens barrel to M.

I also made a mistake on my previous post: I missed the camera the poster was using. But my advice is pretty much the same, except as follows:

a. Buy a book titled "Canon EOS 40D SLR Guide Top Digital Photography" by David D. Bush. There are other useful books written for the Canon 40D, but I bought this one and has been very helpful for me. This book is somewhat a duplication of the owner's manual, except that the author explains every camera function in detail, and presents you with examples (photos, charts, etc.).

b. Shoot RAW.

c. For the photo above: You can set your 40D to aperture priority (Av mode), and Landscape picture stile. Increase the sharpness (if you want) one click or two over the default point. You can set the camera to auto ISO if you want. Leave the focus points on auto (all ON), but change the lens aperture from f/16 though f/22. Use a tripod for landscapes.

The reason why a tripod is important for landscapes is because the best lighting usually is morning, and late afternoon. Since you want to use apertures such as the ones I mentioned, the amount of light reaching the sensor is reduced. But by closing the lens with such apertures, the foreground as well as the background can be in focus. Now, if you use a wide angle lens, then you can open the lens almost all the way and still maintain focus.

Take a look at this photo taken with my 40D: The sky was very bright, but the lens, a Tokina 12-24mm set to 12mm, had a Hoya Ultra Thin CPL. The side of the mountains (to the right) was very dark, and the foreground was darker than the bright sky. I PP the RAW image with PSE6 for the Mac (same for the PC), and lightened the foreground with "fill light." Keep in mind that I could have accomplished the same from the beginning by bracketing as mentioned before. All focus points were used.


For this one I used Av, I believe, 125 ISO, AI Servo, multiple shot. The shutter speed was quite high, since I was controlling the lens aperture and the camera the speed. The background was very bright, but I was only using the middle focus point, since the subject was one bird instead of several.


This one was just the opposite (dark background), but the camera was set the same way.

[RayinAK]

Forgot to mention something very important about lenses: Super wide angle lenses such as the Tokina I used above for the landscape photo, can be used at wider apertures to take such a photo, but longer telephoto lenses often require that you close them to aperture numbers such as f/11 though f/22 if you want to show the foreground as well as the background in focus. The more you open a telephoto's aperture, the shallower the field-of-view. But even with the Tokina lens, depending on light conditions, I close it to f/11 or so.

When taking the photo of the seagull (dark background), the lens was at f/5.6. That's why the trees in background are blurred.

[PhotogGal]

All very helpful information, RayinAK. Thanks for the detailed lesson!