How close do I have to be to a subject for it to be in focus at f/1.8?

[JoeW]

If I wanted to use low apertures (like 1.8-2.8) how far away can I be for it (the persons EYES) to still be tack sharp?
I know that It make the DOF much smaller, But I have no idea how to calculate what distance I should be from the subject. I have tried DOF calculators, but they don't really help.
Please help me clear this up.

I think you're confusing two different concepts here. Lots of people use wide-open apertures (f1.8, f2.0) in low light b/c it maximizes the amount of light coming in to the camera and they want to use only ambient light (either don't have or don't want to use speed lights). And they recognize that the DoF gets narrower as the aperture gets wider.

But you're asking about two separate issues here. First, is the actual DoF. As Braineac pointed out, the actual size of the DoF (even if it's set at f1.8) varies depending upon how far away you are from your subject. But I don't think that's what you mean to ask. My apologies if I'm wrong but it sounds to me what your'e really asking is how close can you be to the subject. And that's a function of the lens, not the aperture. I've got a macro lens that allows me to shoot mere inches from the subject and still be in focus (and with a very narrow DoF).

Also, as others have pointed out, focus and being "tack sharp" aren't the same. You can be in-focus and end up with a blurry picture b/c the light is so slow you're shooting at 1/20th or 1/15th shutter speed. That's going to produce blur with a living object (and that assumes you're rock solid still which you aren't--you pushed down the shutter release, you were breathing...all things that moved the camera). If your focus is on tack sharp photos, it gets in to things like:
--stable platform (camera on a tripod, wireless release)
--quality glass
--stable subject (ideally an inanimate one that doesn't move or breath).

 

[madisonofriel]

How can you make sure it is focused on the eyes?

If you are doing portraits you want to be at f/5.6 - 7.1 for simplicity

You have to learn about your focusing modes on your camera. See my post above
To focus specifically on an eye you have to be in a Single Focus Point mode and thus focus on ONE eye. You CANNOT be in an Auto mode because you are then letting the camera do the thinking.

This does not mean that both eye will be in focus. This is dependent upon your Depth of Field which is based on your distance and aperture .. see the DOF calculators about that.

You might want to tell us what camera you have .. then someone can give you more info on your focusing modes and how to change them.

Keep in mind. just because you have a lens capable of f/1.8 does not mean f/1.8 is the best setting for what you are attempting to do. At some point you may have to ADD more light if you are taking a picture of people
You can raise the ISO which makes the camera more light sensitive, but may introduce noise.
You can lower the shutter which may introduce movement if too low
you can use a lower f/1.8 which allows more light in but gives you a shallow depth of field (the problem here).
or you add light - brighter room or flash

I have a Nikon D3000 and I almost always use manual mode. I will be outdoors with plenty of light, I am just trying to grasp the concept here.

 

[JoeW]

Okay, you've raised another set of issues. First of all, your sample isn't "blurry as heck." The woman's ring is in sharp focus. That's apparently what you were focused on. And at f1.8, the depth of field is narrow enough that the rest of the subjects start to blur. Frankly, I'm a bit surprised that they're in that much focus at f1.8 given that they're outside the depth of field.

Second "how can you make sure it's focused on the eyes..." well, first of all, your camera probably has multiple focal points. You need to program it so it has one center point. One (if you're going to make it a habit of shooting at f1.6 or f1.8 or f2.0). Then you center on the target you want in focus (in this case, one set of eyes--you aren't likely to get both subjects eyes in focus b/c the girl is a couple of inches ahead of the woman...unless you get pretty far back so you're shooting at distance...which is Braineac's point about how DoF expands depending upon distance your'e shooting). Then you recompose the shot (so even though you focused on the woman's or the girl's eyes, they're no longer in the center of the frame). Then you click the shutter.

Third, it looks like you had a bright background or backlighting. So pop a reflector up so it's facing the faces of the two subjects. It will light them up and you can shoot with a wider DoF (f2.8 or 3.5) or a faster shutter speed (which means less blur from movement). Don't have time to schlep around a portable reflector? Then get in the habit of wearing a white shirt and become your own portable reflector.

 

[astroNikon]

How can you make sure it is focused on the eyes?

If you are doing portraits you want to be at f/5.6 - 7.1 for simplicity

You have to learn about your focusing modes on your camera. See my post above
To focus specifically on an eye you have to be in a Single Focus Point mode and thus focus on ONE eye. You CANNOT be in an Auto mode because you are then letting the camera do the thinking.

This does not mean that both eye will be in focus. This is dependent upon your Depth of Field which is based on your distance and aperture .. see the DOF calculators about that.

You might want to tell us what camera you have .. then someone can give you more info on your focusing modes and how to change them.

Keep in mind. just because you have a lens capable of f/1.8 does not mean f/1.8 is the best setting for what you are attempting to do. At some point you may have to ADD more light if you are taking a picture of people
You can raise the ISO which makes the camera more light sensitive, but may introduce noise.
You can lower the shutter which may introduce movement if too low
you can use a lower f/1.8 which allows more light in but gives you a shallow depth of field (the problem here).
or you add light - brighter room or flash

I have a Nikon D3000 and I almost always use manual mode. I will be outdoors with plenty of light, I am just trying to grasp the concept here.

"manual mode' - There's "Manual" mode for aperture, shutter ... Focusing Manual mode and Focus point Manual mode.

this may make more sense after you read it .. it has a video for the d3000 focus point mode too ==> Changing Your Focal Point - Click it Up a Notch

 

[madisonofriel]

If I wanted to use low apertures (like 1.8-2.8) how far away can I be for it (the persons EYES) to still be tack sharp?
I know that It make the DOF much smaller, But I have no idea how to calculate what distance I should be from the subject. I have tried DOF calculators, but they don't really help.
Please help me clear this up.

I think you're confusing two different concepts here. Lots of people use wide-open apertures (f1.8, f2.0) in low light b/c it maximizes the amount of light coming in to the camera and they want to use only ambient light (either don't have or don't want to use speed lights). And they recognize that the DoF gets narrower as the aperture gets wider.

But you're asking about two separate issues here. First, is the actual DoF. As Braineac pointed out, the actual size of the DoF (even if it's set at f1.8) varies depending upon how far away you are from your subject. But I don't think that's what you mean to ask. My apologies if I'm wrong but it sounds to me what your'e really asking is how close can you be to the subject. And that's a function of the lens, not the aperture. I've got a macro lens that allows me to shoot mere inches from the subject and still be in focus (and with a very narrow DoF).

Also, as others have pointed out, focus and being "tack sharp" aren't the same. You can be in-focus and end up with a blurry picture b/c the light is so slow you're shooting at 1/20th or 1/15th shutter speed. That's going to produce blur with a living object (and that assumes you're rock solid still which you aren't--you pushed down the shutter release, you were breathing...all things that moved the camera). If your focus is on tack sharp photos, it gets in to things like:
--stable platform (camera on a tripod, wireless release)
--quality glass
--stable subject (ideally an inanimate one that doesn't move or breath).

Your fist paragraph describes me. I know how CLOSE I can be as indicated by my lens, What I need to know is how FAR away can I be for it to still be in focus.
Before any of this I did a experiment on DOF, and until now, this is how I viewed it:
I placed a measuring tape on the floor 6ft long, placed my camera on my tripod, and began at 1.8. I then placed an object at 6'' focused, and took the photo. I moved the object back about every 6 inches and repeated for every aperture.
Very complicated, but I found what distance produced the sharpest result.
Now when someone tells me it has nothing to do with distance, I am a bit confused...

 

[astroNikon]

Your fist paragraph describes me. I know how CLOSE I can be as indicated by my lens, What I need to know is how FAR away can I be for it to still be in focus.
Before any of this I did a experiment on DOF, and until now, this is how I viewed it:
I placed a measuring tape on the floor 6ft long, placed my camera on my tripod, and began at 1.8. I then placed an object at 6'' focused, and took the photo. I moved the object back about every 6 inches and repeated for every aperture.
Very complicated, but I found what distance produced the sharpest result.
Now when someone tells me it has nothing to do with distance, I am a bit confused...

BUT
what was your camera focusing on. How was it focusing ?

If you have one subject that you move around on a flat area the camera is going to pick up on that object if in an AUTO Focusing mode and move with it.

If you were in Single Point Focusing mode and did not move that focusing point while you moved that object around, then it would be more OOF as you moved it further away or closer.

A camera in an Auto Focus Point mode will try to determine what is the main object of a photo and use that to focus on. In a Manual Focus Point mode it requires the user to select that specific Point (or area).

In a small aperture like f/1.8 if hte camera is in an Auto Focus Point mode it may select someone shoulder as the focus point, thus making things deeper or closer Out Of Focus.

At an aperture like f/11, if the camera focuses on the shoulder the Depth of Field of the aperture will probably put the persons face in Focus too.

look at the link I send you post # 19

 

[madisonofriel]

Your fist paragraph describes me. I know how CLOSE I can be as indicated by my lens, What I need to know is how FAR away can I be for it to still be in focus.
Before any of this I did a experiment on DOF, and until now, this is how I viewed it:
I placed a measuring tape on the floor 6ft long, placed my camera on my tripod, and began at 1.8. I then placed an object at 6'' focused, and took the photo. I moved the object back about every 6 inches and repeated for every aperture.
Very complicated, but I found what distance produced the sharpest result.
Now when someone tells me it has nothing to do with distance, I am a bit confused...

BUT
what was your camera focusing on. How was it focusing ?

If you have one subject that you move around on a flat area the camera is going to pick up on that object if in an AUTO Focusing mode and move with it.

If you were in Single Point Focusing mode and did not move that focusing point while you moved that object around, then it would be more OOF as you moved it further away or closer.

A camera in an Auto Focus Point mode will try to determine what is the main object of a photo and use that to focus on. In a Manual Focus Point mode it requires the user to select that specific Point (or area).

In a small aperture like f/1.8 if hte camera is in an Auto Focus Point mode it may select someone shoulder as the focus point, thus making things deeper or closer Out Of Focus.

At an aperture like f/11, if the camera focuses on the shoulder the Depth of Field of the aperture will probably put the persons face in Focus too.

look at the link I send you post # 19

I just watched the video, and set my camera to single point. I had been trying to figure that out.. thanks

 

[astroNikon]

Essentially
when you are in "Manual" mode you are selecting the Aperture and Shutter

but there's other Manual modes
If you have the lens on Manual, then you focus the lens by hand

Then there's the Focus Point .. an Auto mode or Manual mode
If you are in an Auto mode you are letting the camera pick the point to focus on, which may or may

Your fist paragraph describes me. I know how CLOSE I can be as indicated by my lens, What I need to know is how FAR away can I be for it to still be in focus.
Before any of this I did a experiment on DOF, and until now, this is how I viewed it:
I placed a measuring tape on the floor 6ft long, placed my camera on my tripod, and began at 1.8. I then placed an object at 6'' focused, and took the photo. I moved the object back about every 6 inches and repeated for every aperture.
Very complicated, but I found what distance produced the sharpest result.
Now when someone tells me it has nothing to do with distance, I am a bit confused...

BUT
what was your camera focusing on. How was it focusing ?

If you have one subject that you move around on a flat area the camera is going to pick up on that object if in an AUTO Focusing mode and move with it.

If you were in Single Point Focusing mode and did not move that focusing point while you moved that object around, then it would be more OOF as you moved it further away or closer.

A camera in an Auto Focus Point mode will try to determine what is the main object of a photo and use that to focus on. In a Manual Focus Point mode it requires the user to select that specific Point (or area).

In a small aperture like f/1.8 if hte camera is in an Auto Focus Point mode it may select someone shoulder as the focus point, thus making things deeper or closer Out Of Focus.

At an aperture like f/11, if the camera focuses on the shoulder the Depth of Field of the aperture will probably put the persons face in Focus too.

look at the link I send you post # 19

I just watched the video, and set my camera to single point. I had been trying to figure that out.. thanks

Now try your experiment mentioned in # 20 .
you'll get different results as the camera won't follow the object being repositioned.

 

[astroNikon]

In a Nutshell again, for simplicity

Aperture determines the DEPTH of what is in focus
-- It also control how much light is getting to the sensor

ISO lets you control the sensor sensitivity of light

Shutter - determines how you "stop movement"

I normally set my aperture that I want, and shutter. And let ISO AUTO with a max (based on your camera). You may have to add / bounce light to help the camera though.

THEN
Focus Mode. If I'm in Single Point I'll point to the eye of a subject.
With the proper Aperture for Depth of Field
the the subject(s) should be in focus of what I want in focus.

If in Auto Focus point you allow the camera to determine what it wants to be focused on, which could be anything and it's usually what you don't want, like the fence 40 feet behind people

 

[madisonofriel]

In a Nutshell again, for simplicity

Aperture determines the DEPTH of what is in focus
-- It also control how much light is getting to the sensor

ISO lets you control the sensor sensitivity of light

Shutter - determines how you "stop movement"

I normally set my aperture that I want, and shutter. And let ISO AUTO with a max (based on your camera). You may have to add / bounce light to help the camera though.

THEN
Focus Mode. If I'm in Single Point I'll point to the eye of a subject.
With the proper Aperture for Depth of Field
the the subject(s) should be in focus of what I want in focus.

If in Auto Focus point you allow the camera to determine what it wants to be focused on, which could be anything and it's usually what you don't want, like the fence 40 feet behind people

Thanks so much for the help. You probably want to strangle me at the moment haha.

 

[astroNikon]

In a Nutshell again, for simplicity

Aperture determines the DEPTH of what is in focus
-- It also control how much light is getting to the sensor

ISO lets you control the sensor sensitivity of light

Shutter - determines how you "stop movement"

I normally set my aperture that I want, and shutter. And let ISO AUTO with a max (based on your camera). You may have to add / bounce light to help the camera though.

THEN
Focus Mode. If I'm in Single Point I'll point to the eye of a subject.
With the proper Aperture for Depth of Field
the the subject(s) should be in focus of what I want in focus.

If in Auto Focus point you allow the camera to determine what it wants to be focused on, which could be anything and it's usually what you don't want, like the fence 40 feet behind people

Thanks so much for the help. You probably want to strangle me at the moment haha.

hahhaha

I just had to repeat post # 12 in various ways until you finally got it.

 

[KmH]

You need to tell us what camera you use, what lens focal length you use, what focus mode, and focus area mode you use if you're using auto focus.

The only minimum you need to be aware of is the minimum focus distance the lens you are using is capable of.
At distances closer than than minimum focus cannot be achieved regardless the lens aperture you use.

Depth-of-field is a zone of distance in front of the camera that will be acceptably in focus.
How far that zone is from the camera is determined by how far the the point of focus (PoF) is from the camera.
IMPORTANT NOTE: The zone is parallel to the image sensor in the camera.

With a 50 mm focal length, the aperture set to f/1.8, using a 1.6x crop sensor camera, and a point of focus distance of 6 feet the total DoF is only 0.29 feet (3.5 inches)
Plus 49% of the total DoF (1.75" is front of the point of focus while 1.75" is behind the PoF.

In the photo you posted not all of the eyes are the same distance from the camera.
But in that photo it looks like the fingers/ring are in the DoF zone and in focus, which means the subject's eyes were OOF (out of focus) because their eyes were beyond the far limit of the DoF.

Apparently you need to develop your understanding of how to focus or use auto focus, and your understanding of DoF. DoF is likely the most difficult concept inexperienced photographers have to learn to manage.
Understanding Depth of Field in Photography
Understanding Camera Autofocus

 

[wfooshee]

In the image you posted, it appears the camera focused on the closest object in its view, the hand, or maybe the butterfly. Unless you use single-point single-servo AF, you have no control over where the camera focuses.

 

[KmH]

Unless you use single-point single-servo AF, you have no control over where the camera focuses.

That is not a true statement if the camera is a Nikon DSLR. The single point used to AF can be controlled by the user in AF- C focusing mode.

 

[Tinstafl]

You can control the focus if you set the camera to do that with the button on the back. You can put it right on the eye. Now you DOF is a combination of distance to the subject, focal length, aperture and sensor size. Get a nap for your phone and play with it. In shooting you can control all but sensor size but you have tradeoff. If I can not move back further then I have to increase the f stop. Make it bigger but as a result i either have to have a longer exposure and that can cause blur or up the ISO.