Auto Focus Mystery
Aug 21, 2013 11:24:31 #
I understand the mechanics of focus, and the options available to me with my d5100 and Olympus PS, but my question is this.
Why would autofocus ... on any camera ... be soft if the user has chosen the correct settings and the camera is performing well ? In other words, how can a camera "botch" a well composed shot under ideal circumstances ?
I'm not complaining about my cameras ... botched is usually my fault ... but more in general. On many of the photos posted here the focus is obviously off a bit, the poster knows it, and the camera brands and capabilities (and user skills) vary widely. Isn't that what auto focus is supposed to remedy ? I'm not sure there is a specific answer to this, but am curious as to just what makes a correctly set up shot seem mildly out of focus. Thanks
Why would autofocus ... on any camera ... be soft if the user has chosen the correct settings and the camera is performing well ? In other words, how can a camera "botch" a well composed shot under ideal circumstances ?
I'm not complaining about my cameras ... botched is usually my fault ... but more in general. On many of the photos posted here the focus is obviously off a bit, the poster knows it, and the camera brands and capabilities (and user skills) vary widely. Isn't that what auto focus is supposed to remedy ? I'm not sure there is a specific answer to this, but am curious as to just what makes a correctly set up shot seem mildly out of focus. Thanks
Aug 21, 2013 11:30:43 #
It looks like your camera has chosen an aperture that is too large (small number) which gives you a very narrow depth of field of focus thus missing your subject. Try aperture priority and use something like F8 or F11. You may have to adjust your ISO to achieve this with your current lighting environment. Keep watch on your histogram also.
Bill R.
Bill R.
Aug 21, 2013 11:47:38 #
tom hughes
Loc: Phila Pa
Automatic kind of equals best average settings very good but never exact. I shoot Manual 90 percent of the time, Av & Tv the other ten percent. You will learn more from your mistakes shooting manual, you learn nothing from shooting on automatic.
Aug 21, 2013 11:48:49 #
kemo wrote:
I understand the mechanics of focus, and the optio... (show quote)
You answered the question yourself. Usually it's operator error. Sometimes it's because the camera isn't setup for the proper settings - again operator error. Sometimes it's because the photographer shook or moved as the shutter was released - operator error. Wrong shutter speed - operator error. The wind caused the camera to shake or the tripod wasn't sturdy enough or the tripod was not weighted properly - operator error. I'd say 99% of the time - operator error.
But faulty equipment can be the cause. Or, inferior equipment can be the cause e.g. cheap lenses.
Sometimes here on UHH it is just simply they eye of the beholder. I've seen some people post images that they are very proud of but I'd have trashed the second I shot it, or I'd have never press the shutter button. It's hard to say exactly why an image is OOF. But again, 99% of the time it's - operator error.
Aug 21, 2013 12:30:56 #
Auto focus is not perfect. Many times the focus point will be not what you intended, especially if you use multi-focus points. I do use auto focus at times, but do not trust it, so I take multiple shots to make sure I get one in focus and the focus where I want it. If focus is critical, I always use manual focus, take a shot then magnify the image in the viewfinder or LCD and make sure.
It is best to turn off all the focus points except 1 and place that point where you want the focus to be. Even that will miss at times, especially with a narrow DOF. When I am shooting at f/1.4 @ 4 feet from the subject and I am hand held, if I move 1 inch from the time I focus til the time I push the shutter button, I have missed the focus.
So in short, there is more than 1 thing involved in getting the focus right. If you want to be sure, use a tripod and manual focus.
It is best to turn off all the focus points except 1 and place that point where you want the focus to be. Even that will miss at times, especially with a narrow DOF. When I am shooting at f/1.4 @ 4 feet from the subject and I am hand held, if I move 1 inch from the time I focus til the time I push the shutter button, I have missed the focus.
So in short, there is more than 1 thing involved in getting the focus right. If you want to be sure, use a tripod and manual focus.
kemo wrote:
I understand the mechanics of focus, and the optio... (show quote)
Aug 21, 2013 12:53:01 #
Thank you (all) for responding. I routinely compare my shots with those posted here at UHH and find myself wondering two conflicting thoughts.
Bad: This shot is obviously out of focus but the poster does not seem to notice.
Good: How on earth did the poster manage getting such a beautiful shot under such challenging circumstances.
Thanks again for responding
Bad: This shot is obviously out of focus but the poster does not seem to notice.
Good: How on earth did the poster manage getting such a beautiful shot under such challenging circumstances.
Thanks again for responding
Aug 21, 2013 13:15:57 #
visualconnections
Loc: Boerne, texas
I have the same problem with my 7D! I know it's me, and sometimes when I take a deep breath, let it out, then shoot, I'm ok but when I'm shooting a wedding and moving all over the place I do the auto focus because i don't trust my eyes and I do take a lot so if one is blurry I just toss it. I have never tried turning off all the focus points so I will try that too! Good luck!
Aug 22, 2013 06:21:54 #
have you adjusted the dioptre to your eyesight?
- detach lens, (so you are adjusting focus on focus point, not image) - adjust dioptre (next to viewfinder) so focus points are sharply in focus. (easier against a white, or light background) Re-attach lens.
- detach lens, (so you are adjusting focus on focus point, not image) - adjust dioptre (next to viewfinder) so focus points are sharply in focus. (easier against a white, or light background) Re-attach lens.
Aug 22, 2013 06:42:03 #
Thank you. I've already adjusted the diopter with a lens attached. Going to try without. Thanks
Aug 22, 2013 09:27:15 #
kemo wrote:
I understand the mechanics of focus, and the optio... (show quote)
On Nikon- be sure the little green light is holding steady!!!!
Aug 22, 2013 09:44:50 #
kemo wrote:
Why would autofocus ... on any camera ... be soft if the user has chosen the correct settings and the camera is performing well ? In other words, how can a camera "botch" a well composed shot under ideal circumstances ?
Does you camera by any change have a portrait setting?
If that is set, it could also give you soft focus.
EstherP
Aug 22, 2013 10:40:25 #
kemo wrote:
I understand the mechanics of focus, and the optio... (show quote)
Kemo,
In order to resolve your problems you need to set some standards for capturing an image with both good exposures, and sharp focus. From these standards you can deviate for creative effects and know what you are doing with the camera.
Set your camera up for a standard photograph: (You may need your owners manual)
1. ISO = 200.
2. Aperture = Aperture Priority (Av).
3. Aperture Value = f/8.0.
4. Set both Exposure Metering, and Auto Focus to "Center Spot".
Select a well illuminated day and subject.
When composing the image in the viewfinder, place the center spot on the principle subject, press the shutter half way down to lock focus and exposure. With the shutter button still half way pressed re-compose the image to your liking. Press the shutter all the way down to capture the image.
In order to troubleshoot focus problems we need to begin with a standard image capture, then we can look into other areas for problems.
In many problems the issue can be resolved to Operator Error.
Michael G
Aug 22, 2013 10:59:29 #
warrior wrote:
On Nikon- be sure the little green light is holding steady!!!!
Yeah, but.... the little green light will tell you something is in focus, but not necessarily what you wanted, partcularly in low light or with non-contrasty sujects.
Aug 22, 2013 11:17:50 #
OddJobber wrote:
Yeah, but.... the little green light will tell you something is in focus, but not necessarily what you wanted, partcularly in low light or with non-contrasty sujects.
The Auto Focus function on many modern DSLR cameras performs its task by measuring the brightness/contrast range within the selected focusing point. When contrast/brightness cannot provide a range the Auto Focus tends to hunt for contrast. The green light flashes while the focus motor hums.
When this occurs you may be able to pop-up the on camera flash and allow it to provide burst flashes for Auto Focus in dark compositions. An alternative is to switch to Manual Focus, operate the focus ring on the lens by hand, and if illumination provides use "Live View" to magnify the LCD display 10x.
Michael G
Aug 22, 2013 11:59:25 #
sirlensalot
Loc: Arizona
All other things being correct, and in the absence of using manual focus, is it possible the lens may have a front or back focus issue? Do not know of your particular model has micro-adjust capabilities, but it may be worth it to send camera and lens to manufacturer and have it checked and / or adjusted if needed. Just a thought.
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