newbie question about focus/clarity

[leet]

I'm frustrated by the lack of adequate focus in my photos. I've been playing around with shutter speed and other settings, but no luck.

Using the viewfinder, I snap the photo after the red autofocus dot flashes on my subject's face. But when I copy the photos onto my computer, I find that roughly one in ten is of adequate clarity.

Here is a typical photo.

And here some info for that photo:

Exposure time: 1/60 sec.
F number: f/5.6
Focal length: 135 mm.

I'm using a Canon T3i.

I appreciate any tips/advice!

 

[Robin Usagani]

First of all, your exposure time is awfully slow for subject that is moving AND for that long of a lens. Dont get focus and motion blur mistaken. You probably need at least 1/200 or perhaps 1/100 if you are able to prop your camera/lens on a solid surface.

 

[SoCalTiger]

I'm frustrated by the lack of adequate focus in my photos. I've been playing around with shutter speed and other settings, but no luck.

Using the viewfinder, I snap the photo after the red autofocus dot flashes on my subject's face. But when I copy the photos onto my computer, I find that roughly one in ten is of adequate clarity.

Here is a typical photo.

And here some info for that photo:

Exposure time: 1/60 sec.
F number: f/5.6
Focal length: 135 mm.

I'm using a Canon T3i.

I appreciate any tips/advice!

Your shutter speed is too slow for that focal length assuming these are handheld shots. You always want to be faster than 1/x sec (where x is your focal length). For 135mm, you'd want faster than 1/135mm (1/160 or 1/200). In that lighting, you'd have to increase your ISO and/or have a bigger aperture (smaller F-number). You could also try using a tripod in these situations but if the subject is moving, you're still subject to motion blur at 1/60sec.

 

[KmH]

The rule of thumb for shutter speed is 1/the focal length of the lens. You used a 135 mm lens so you need about 1/135 as the slowest shutter speed you use. You used a shutter speed over twice as long 1/60.

Next! Focus and depth-of-field (DoF) are in fact the same thing. How much DoF you use determines how far in front of, and how far behind, your point of focus (PoF) will be acceptably sharply in focus.

The online DoF calculator at http://dofmaster.com/dofjs.html shows that using a T3i, 135 mm lens, lens aperture of f/5.6, and assuming a focus point distance from the camera of 20 feet, the total DoF was only 17" deep. Further 48% of that 17" (8") was in front of the PoF, and 53% of the 17" (9") was behind the PoF.

If the PoF was only 15 feet from the camera, the total DoF would only be 9.5" deep, and split closer to 50%/50% than the 48%/52% at a PoF of 20 feet.

By the way, in photography clarity is a measure of mid-tone contrast and has a somewhat different relationship to focus, however, when editing post process, adding some clarity (mid-tone contrast) can make a photo look a bit sharper.

 

[SCraig]

One of two things is going on: 1) You are seeing motion blur (the subject is moving while the shutter is open) or 2) You are not focusing on her face. At f/5.6 and135mm, KmH noted, your depth of field is very shallow however the writing on the board behind her is properly in focus. This tells me that you either focused on the writing on the board OR she moved slightly while the shutter was open.

 

[Espike]

I totally understand your frustration. As someone who is new to photography, I too am noticing a lot of blurry pictures. Everything that they have told you above is correct however, in this situation, you would have had to bump the ISO pretty high to use a shutter speed that was appropriate. One thing that helps is a faster lens, but even then you would have wanted to stop it down for maximum sharpness. In this situation a tripod, or a flash would have helped the most (IMO).

 

[leet]

It's really great that all of you took the time to reply. Thank you very much. Knowing what to experiment with and identifying some next steps is very helpful for alleviating the frustration.

And yes, the photography for beginners book is on its way.

 

[KmH]

Add this link to your favorites list - Digital Photography Tutorials

Here are some more - http://www.thephotoforum.com/forum/...-forum/267492-info-those-new-photography.html

 

[Carny]

In the example you gave the ISO was already at 4000 and the lens was wide open, so going even higher on ISO would have been the only way to increase shutter speed without more light (or switching to a faster lens). There is already a bit of noise, I'm not sure how much higher you could go and still get a usable image.

Besides what everyone else has already said, almost every lens loses sharpness when set wide open (lowest F-number). You didn't really have that option in the photo you posted, just for future reference.

 

[morganza]

The rule of thumb for shutter speed is 1/the focal length of the lens. You used a 135 mm lens so you need about 1/135 as the slowest shutter speed you use. You used a shutter speed over twice as long 1/60.

Next! Focus and depth-of-field (DoF) are in fact the same thing. How much DoF you use determines how far in front of, and how far behind, your point of focus (PoF) will be acceptably sharply in focus.

The online DoF calculator at Online Depth of Field Calculator shows that using a T3i, 135 mm lens, lens aperture of f/5.6, and assuming a focus point distance from the camera of 20 feet, the total DoF was only 17" deep. furthre 48% of that 17" (8") was in front of the PoF, and 53% of the 17" (9") was behind the PoF.

If the PoF was only 15 feet from the camera, the total Dof was only 9.5" deep, and split closer to 50%/50% than the 48%/52% at a PoF of 20 feet.

By the way, in photography clarity is a measure of mid-tone contrast and has a somewhat different relationship to focus, however, when editing post process adding some clarity (mid-tone contrast) can make a photo look a bit sharper.

Wow, thanks a lot!