Distance to Subject vs. Aperture

[christiehw]

Hello all,

I was just reading another great post on no-flash photography for a wedding and one of the posts brought up a question for me that has just been driving me crazy. My question is this....I usually try to shoot wide open f1.4 or f2.8 depending on the lens I am using. I have to be spot on with my focus....usually on the eyes, because if I am not spot on, one or both of the eyes are blurry. How does a wedding photographer or group portrait photographer shoot with a wide open aperture and get everybody in focus? The post I read talked about watching the distance to subject versus aperture to make sure people are in focus. Am I missing something? Does the distance you are away from the subject change how much is in focus? Meaning, if I take a portrait of my son and am 1 foot away from him, I only get a small and very precise focal point.....but if I take the same portrait at the same aperture, but am 10 feet away and zoomed in, will I get more of his face in focus? I hope this question makes sense, because I am really confused. As if you couldn't tell! Any clarification would be so greatly appreciated!

Thanks so much in advance for your time!

[inkista]

Yup, the farther away you are from the subject the more DoF you have to work with. This is also why macro photography almost always involves a very thin DoF. With wedding photographers and group shots, another alternative is to stop down and use a flash.

[christiehw]

Thank you inkista for the quick reply! I have one slightly unrelated follow up question.....So if I am photographing say a group of three people in a low natural light situation and don't want to use a flash and have my 24-70mm lens at f2.8, I am assuming that it behooves me to be as far away from them as possible to get more of the subjects in focus? Does zoom play a part in this equation? Okay, here comes the unrelated part of this question....In this situation, should I use autofocus or should I use one of the 9 point focus points? If I use one of the 9 point focus points, where should I place my focus in this group shot situation? (Assuming that the three subjects eyes are on different planes.)

[kencaleno]

I have been a wedding photographer for 48 years, and I can assure you that you cannot use a wide open F2.8 lens for groups shot as you suppose.- For the dof you would need, you would never recognize the people in the image from that distance- you would never go further than F4; -F8 is the norm for weddings ( Ever heard the saying: "F8 and be there?") For what you want to do I would suggest a 17mm or 18mm lens at F4.Just make sure you have adequate lighting. Regards, Ken PS Manual focus is the way to go.

[t blanchard]

Here is a depth of field calculator - you input your distance from the subject, your f/stop, your and your focal length - and it will tell you the depth of field range:

http://www.dofmaster.com/dofjs.html

[kirbinster]

One other point to ponder, typically most lenses are not at their sharpest when wide open. So, even if you could get the DOF at f/1.8 you would probably want to close down about two stops to get a sharper image.

[sybren]

Originally Posted by christiehw

Does the distance you are away from the subject change how much is in focus? Meaning, if I take a portrait of my son and am 1 foot away from him, I only get a small and very precise focal point.....but if I take the same portrait at the same aperture, but am 10 feet away and zoomed in, will I get more of his face in focus?

Distance and zoom both influence the DOF. When you move away from your subject, the DOF gets larger. However, when you zoom in again, the DOF gets smaller. This happens in equal amounts, so in these cases you have the same DOF:

1. You are close to your son, and zoomed out so that his face just fits the frame
2. You are far away from your son, and zoomed in so that his face just fits the frame

[Ishyid]

Originally Posted by sybren

Distance and zoom both influence the DOF. When you move away from your subject, the DOF gets larger. However, when you zoom in again, the DOF gets smaller. This happens in equal amounts, so in these cases you have the same DOF:

1. You are close to your son, and zoomed out so that his face just fits the frame
2. You are far away from your son, and zoomed in so that his face just fits the frame

Sorry to interupt, but what is DOF?

Thanks

[LoveDSLR]

Originally Posted by Ishyid

Sorry to interupt, but what is DOF?

Depth of Field (DOF).

[LoveDSLR]

Originally Posted by christiehw

My question is this....I usually try to shoot wide open f1.4 or f2.8 depending on the lens I am using. I have to be spot on with my focus....usually on the eyes, because if I am not spot on, one or both of the eyes are blurry. How does a wedding photographer or group portrait photographer shoot with a wide open aperture and get everybody in focus?

You should not equal low light with wide apertures only. Pros can use high ISO as much as 6400 (e.g., Nikon D3/D700) if necessary.

However in your case, Ken's advice about 17mm or 18mm lens (more DOF) at F4 is a start.