focus isses: DOF vs shutter speed vs AF settings

[CGR]

I'm getting frustrated with focus issues. I use auto-focus on a Canon 5D Mark III, mainly been shooting with a pretty fast 85mm 1.8 prime. So, can't really blame slow gear.

I mostly shoot my fast moving toddlers and their friends (not a pro, with no plans to be). I love shooting fairly wide-open with primes but have some DOF issues with moving subjects. But not sure if it is the movement with DOF or the variable shutter speed in AV mode. Since high ISO is so great with Mark III, I'm thinking of shooting in manual with aperture set for the subject(s) and a fixed shutter speed (150 outdoors?) with ISO on auto? I don't have the time to meter every time I turn around. I do get tack-sharp images when my subjects aren't moving (which is hardly ever).

Here is an example of the annoying focus issues. This could be a cute shot, if it was actually in focus. Settings: F/4, 1/100, ISO 400 with the 85mm 1.8


What are your tips for getting super sharp images (that still have great bokeh)? Any help appreciated!

 

[CGR]

BAH! Just realized this needs to be in the beginners forum and can't figure out how to move it. SORRY!

 

[KmH]

You can't move it. FWIW - Bokeh is not adjustable, but DoF is.

When using aperture priority (Canon AV, Nikon A) mode, you have to keep an eye in the viewfinder on what shutter speed the camera is selecting. Many action sports photographers also use Av mode, but watch that shutter speed closely.

Looks like some motion blur of the child's hand, face and the tops of their hats, because the hand/face was moving and it looks like wind was blowing the tassels on their hats.
Your shutter speed was only 1/100, and to slow to stop a moving limb and wind whipped cloth.

The rest is from the DoF being very shallow. Mom and child are at different enough distances from the camera because they are on a diagonal to the plane of focus that is essentially parallel to the camera image sensor. (there will likely be some amount be some amount of field curvature caused by the lens)

I'm guessing your point of focus was about 8 feet from the camera, making your total DoF about 7 to 7.5 inches. That Dof would have been distributed at 48% in front of the point of focus and 52% behind the point of focus. In distance, that distribution of the total DoF would be 3.5 inches in front, and 4 inches behind the point of focus.
A 50 mm lens, set to f/4, using a 4.75 foot point of focus distance would give almost the same exact DoF as did your 85 mm lens at f/4 and an 8 foot point of focus distance.

If you don't follow all of that, you might want to learn/understand more about controlling depth-of-field. Understanding Depth of Field in Photography

Controlling focus when using a wide aperture and a close point of focus distance is a common problem for inexperienced photographers.
Apparently, many don't understand how lens focal length, and point of focus distance affects DoF.

 

[unpopular]

You can't move it. FWIW - Bokeh is not adjustable, but DoF is.

ehhhhh. i'm going to bed right now. but all I have to say is: flektogon.

certain distance combinations will, to some extent, affect bokeh aggressiveness and swirl. However, it's more noticeable with certain wider lenses. Even my Minolta 50/1.8 will, on some fluke occasion, go tilt-a-whirl on me wide open. A quality which I just cannot stand.

 

[BrianV]

Looking at the 1:1 image, I see motion blur more than the image being out of focus. The image of the child's face appears to be smeared going across the horizontal. 1/100s, F4, ISO 400: must have been subdued lighting - Dusk? I would up the ISO and try a higher shutter-speed. 1/100th does not leave much margin for hand-holding an 85mm lens. "Film Days"- the lowest hand-held shutter speed was the inverse of the focal length. Those were the days when a 4x6 print was typical. Digital: much more critical.

 

[bratkinson]

I just upgraded to a 5D3 and the 61 auto-focus points can seem like a real puzzle. Controlling the AF selection points as well as shooting in single-shot or AI servo as appropriate can make a major difference in the results.

While browsing through a bunch of YouTube Canon 5D3 videos I found, I found this 3 part presentation (about 30 mins per each part) about the Canon AF system. Although this was presented before the 5D3 hit the street, it's still fully applicable to the 5D3 as well as any other Canon cameras in the past 5 years or so...

Part 1 of 3: A Look at The Canon Autofocus System - YouTube

Here's a good one on AF point selection, specific to the 5D3 as well...

Canon EOS 5D Mark III - Tutorial AF Area Selection 1/14 - YouTube

 

[CGR]

Bratkinson- thanks so much! That is really helpful. I've been wondering about the different modes- can't wait to check those out!

Brian- right on. It was dusk. So I know about 1/100 is my min for this lens. I don't mind some motion blur in the fabric but I NEED sharp faces. You think 150 would have been better or 200? Higher? I know I could have gone much higher on my ISO and still have gotten a great image. I have a super sharp shot at f 5.6 and ISO 1250 that came out great (in the same light).

I do understand a bit about DOF. I think this calculator is great: Online Depth of Field Calculator But I guess it isn't all second nature when moving fast in the field. Clearly I'm still learning and I really appreciate all of the less critical suggestions.

What settings do you think would have nailed this shot? What do you think is the best shooting mode for fast moving subjects? Is my manual settings with just auto ISO idea stupid crazy?

Happy Friday!

 

[BrianV]

With digital- and all the ability easily magnify the image, I tend to prefer 1/250th and 1/500th as a base shutter speed unless the subject is holding still. At F5.6 and ISO 1250, the shutter speed in the same light should have been around 1/200th. I think you answered your own question!

I tend tp up the ISO manually as required, and open up the lens for a comfortable shutter speed. But I'm a control freak.

Auto-ISO these days, with new sensors and post-processing software for noise removal- like any mode on the camera, as long as you understand it and the limitations: it's a useful tool.

 

[rambler]

CGR, sharp focus is always a challenge, but hey that focus of the child does not bother me. You got the face sharp enough for me! But, try using continuous shutter speed also. That helps to freeze motion. If your camera is handheld tyr the ISO at 1600 and do not worry about noise. Wouldn't you rather have noise than blur!

There are some 1/3 2/3 rules of thumb about focal distances. Usually I just wing it with a variety of different focus points. Do you have an iphone? There is a convenient free app that calculates the numbers for you. I thinks it EsayDOF.com or maybe it's SimpleDOF. Google it!

Focus on the eyes!

Here is another tip used by sports photographers....Set a button on the outside of your camera, ie. on the body, that does the focusing instead of having to push the shutter release half way down to focus. Why? Your camera no longer has to focus, then shoot. You are already focused so that when you push the shutter it takes the image right away. Keep your thumb on the button and just wait for the right moment to click away!

On the 5D: Press the menu button on the back of your camera, goto custom function IV-1 menu, choose Metering start/metering + AF start.

(Thanks to Scott Kelby, Digital Photography, Book 4, p. 126)

(Nikon users: Custom Setting Menu, #f5, AF-ON and AE/AL button will then initiate the focus)

Have you tried ISO Sensitivity auto control? This allows you to set a maximum ISO and a Minimum shutter speed. For example set the speed at 1/125 and the ISO at 1600 and your camera will not go slower than 1/125 or higher than ISO 1600. This prevents you from missing a shot if your camera had been on a slower shutter speed and you did not have time to change it in order to get the shot.

 

[jwbryson1]

Controlling focus when using a wide aperture and a close point of focus distance is a common problem for inexperienced photographers.

Apparently, many don't understand how lens focal length, and point of focus distance affects DoF.

This was an excellent response Keith! Question -- under this scenario would you recommend to an amateur photographer that the focus point be about 1/3 of the way into the subject? In this case, maybe focusing on the mom's left cheek or the boy's chin?

 

[KmH]

Why focus 1/3 of the way in, when the DoF distribution is actually close to 50/50?

Focus 1/3 of the way in when the DoF distribution is close to 33/66. In the case of the OPs camera and lens, at f/4 33/66 doesn't happen until the point of focus distance is about 60 feet away.

In other words, a short focus distance usually results in a DoF distribution close to 50/50, and as point of focus distance is increased the DoF distribution progresses towards 33/66.

Online Depth of Field Calculator

 

[The_Traveler]

Managing DOF using shutter speed, aperture and iso is a difficult task of you try to do it all yourself.
Auto iso is an enormously powerful aid for this.

Look at the priorities - adequate DOF but not too much, minimum shutter speed, reasonable color noise

Shoot aperture preferred because you want to control the dof (the crucial issue)
set a minimum shutter speed (to be certain you stop the motion.) but you don't care about anything but stopping the motion
and set the iso range to what you can accept.

I'd rather get some color noise from high iso than an totally unusably blurred image.

And if you can't get the shot, well, sometimes there isn't enough light to get the shot.

 

[jwbryson1]

Why focus 1/3 of the way in, when the DoF distribution is actually close to 50/50?

Focus 1/3 of the way in when the DoF distribution is close to 33/66. In the case of the OPs camera and lens, at f/4 33/66 doesn't happen until the point of focus distance is about 60 feet away.

In other words, a short focus distance usually results in a DoF distribution close to 50/50, and as point of focus distance is increased the DoF distribution progresses towards 33/66.

Online Depth of Field Calculator

I understand that---I was not being specific enough and was making several assumptions, the first of which was that the OP did not check the DOF calculations first and was shooting and hoping to nail the focus. Of course, it makes sense that if you can do a quick calculation of the DOF you could get a better idea of where to focus.

 

[unpopular]

good figgin' god's gravy people.

Just use the DOF preview. On wider lenses, use the DOF scale.

 

[rambler]

You lens has an f/1.8 option making it a "fast lens", why not try that setting? The closer you move in, the more blur should appear in the background as DOF would get shallower. Your camera might have "subject tracking-AF" which means that the focus point or area will follow the subject as it moves through the frame, ie. crawling baby. In this setting you could also focus on a point in the center of your camera say the baby's face then just move the camera to get the face out of the center and the focus point will move with the baby. Working with this method means that you do not have to touch the dial to move the focus point. (On the Nikon I have D7000 you use the OK button to activate or stop the tracking once you are set to that mode)
If you are having trouble getting one part of an image in focus and not another, take two photos one with part A in focus, one with part B in focus and then combine them in Photoshop and you should be able to have part A and Part B both in focus in the one combined image. A tripod would help with alignment issues, but PS can do an alignment also. There is software that does this, too, named Helicon Focus

I would also try AF-C, Continuos servo.

You have to like that "servo" term anyway, and maybe I will have a much better idea about all these issues when our first grandchild arrives in February. These are ideas you might try though I have not used them myself, so hopefully others will discredit my points as necessary.