Focus Issue

[chris16]

OK... Please set aside EVERYTHING about this picture other than the focus problem I'm having. My issue is baby appears to be in focus and Mom is not. Yes I know baby is not tack sharp (the hair is) but not baby and Mom. Here are the settings I see.

I mostly have always done landscape photography and this is my first attempt at modeling.

Exposure 1/160 F1.8
FL 85mm
ISO 200
Lens 85mmf1.8
Nikon D700
Shot in basement studio with one strobe (I know the shot is a little hot) Just the focus issue please.


Question is why aren't both subject in focus?

If you don't have anything constructive to say please keep it to yourself. I know I have allot to learn and criticizing me wont help.

 

[Natalie]

It's because you're shooting at f/1.8. Use a (much) smaller aperture and you'll be able to get both in focus.

 

[chris16]

Reading another thread... was I too close to my subjects? Is my 85mm lens just too much for a studio setting? 10 -15 feet from subject? I'm so used to outdoors I'm not used to these issues. Thanks

 

[Mrgiggls]

Yep..the focus point is on the childs hair...everything closer and further is out of the DOF plane. If that 85 would have been on a DX sensor you'd have been further back and it would have given you a deeper DoF plane, but on that FX you were closer and thus making it thinner. I was actually surprised that it was a 85mm lens until I looked further down and saw the body.

Shooting this at say f/2.8 or so would give a much more usable DoF as well as getting you into the sharpness sweet-spot....Almost any lens is sharpest a few f-stops down from wide open.

 

[Natalie]

A longer lens (and a greater shooting distance) will emphasize DoF issues, but the main problem you're having is an extremely shallow depth of field, and the subjects are at different distances from camera. At f/1.8, you'll be able to get one subject in focus, but not the other if they are closer or further from lens compared to the first subject. Mom looks pretty far behind the baby, so try shooting at f/5.0 and see if that helps.

 

[pgriz]

At f/1.8, and 10 ft. distance, you have about 2 inches of acceptable focus in front and another 2 inches in the back. That's a total Depth of Field (DOF) of about 4 inches. If you want a DOF of (say) 2 ft. (ie, 1 ft. in front and 1 foot behind), then you need to shoot at f/16 at a distance of 10 ft.

 

[chris16]

I was just taking a few test shots with your feed back and your guys are right!! I bumped it up to f14 and it helped a bunch! Like I said... Lots to learn about studio and models. Thanks guys!

 

[chris16]

Thank you very much!

 

[pgriz]

Chris, you will find this link useful: Hyperfocal Distance and Depth of Field Calculator - DOFMaster

 

[KmH]

I was just taking a few test shots with your feed back and your guys are right!! I bumped it up to f14 and it helped a bunch! Like I said... Lots to learn about studio and models. Thanks guys!

The issue you were having was about a basic photography fundamental - controlling depth-of-field (DoF).

DoF is likely the single most misunderstood basic photography fundamental.

DoF is controlled by a number of factors:

• image sensor size
• lens focal length
• focus point distance
• lens aperture
• focus point to background distance

The smaller the image sensor is, the deeper the DoF is. Point & shoot cameras generally have small image sensors. That is why they also generally produce a deep DoF even when small lens apertures are used.

The lens focal length has a much more subtle effect on DoF. If I shoot a subject using a 50 mm lens set to f/4, and then shoot the same subject using a 200 mm lens also set to f/4 so the subject has exactly the same scale in the image frame, I will have to be further awy from the subject to use the 200 mm lens. But, the DoF will be exactly the same with the 200 mm lens as it was using the 50 mm lens. The difference is the background elements in the image frame are magnified by the 200 mm lens. If those background elements are out-of-focus (OOF) they will seem more blurred because they are magnified by the longer focal length lens.

Focus point distance has the biggest effect on the DoF. The further the focus point is from the camera the deeper the DoF becomes.

Lens aperture also has an effect on how deep DoF is, and lens aperture also affects the distribution of the DoF.
Sharpest focus is at the point of focus. Focus sharpness starts falling off in front of, and behind the focus point. When DoF is shallow, the focus sharpness drops off quickly in front of, and behind the point of focus. When DoF is deep focus sharpness drops off much slower with distance from the point of focus.
The distribution of the DoF is usually near 50% in front of, and 50% behind the point of focus. Depending on the lens focal length and other controlling factors the DoF distribution can be 25%/75%.
In your example, according to - Online Depth of Field Calculator - at f/1.8 the DoF distribution of your 85 mm was 49%/51%, and at f/14 it was 44%/56%.

You may have noticed that the DoF distribution is always deeper behind the point of focus. so to get those nice blurred backgrounds the subject has to be well away from the background.

Understanding Depth of Field in Photography