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

[greybeard]

As close as your lens will focus, it depends on the lens. A standard zoom like an 18-50 will get pretty close, maybe 12 inches or so. But, a macro lens will get you very close so, it just depends on the minimum focusing distance of your lens.

 

[wfooshee]

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.

But if you recompose after focusing, the camera will refocus on that single point as you compose. The single point selected becomes a starting point for the focus operation rather than The Focus Point. Changing what's under that point in the frame will change the focus in AF-C.

 

[Bebulamar]

I try another road, since it seems to me that you suppose there is a link between aperture and distance.
Aperture is not constrained by distance: you can use 1.8 at any distance, from the minimum allowed by the lens to infinity. You are in one place, your subject is at another one, and that's almost all.
To have eyes on focus, you need to focus on (one of) them, and DOF will be around them (from slightly in front, to slightly back). DOF calculators give you how much in front and how much on back (or the sum of both). As told by others, if eyes are not parallel to the sensor, at those small apertures there is some risk that one is out of focus, because outside the DOF limits.[/QUOTE]
So, let me see if I have this straight...
As long as you're the minimum away from the person facing you, and you focus on the eyes, You can use whatever aperture you want?
It makes sense, but I cant seem to be able to do it.
For example, this was taken at 1.8 in a low light room... and it is blurry as heck.
How can you make sure it is focused on the eyes?[/QUOTE]

The attached picture is very good. The butterfly is sharp and you focus on the butterfly which I would too but I would use at least f/8 or f/11 to get the faces in decent sharpness. Didn't you have enough light to use a smaller aperture like f/8?

 

[madisonofriel]

I try another road, since it seems to me that you suppose there is a link between aperture and distance.
Aperture is not constrained by distance: you can use 1.8 at any distance, from the minimum allowed by the lens to infinity. You are in one place, your subject is at another one, and that's almost all.
To have eyes on focus, you need to focus on (one of) them, and DOF will be around them (from slightly in front, to slightly back). DOF calculators give you how much in front and how much on back (or the sum of both). As told by others, if eyes are not parallel to the sensor, at those small apertures there is some risk that one is out of focus, because outside the DOF limits.

So, let me see if I have this straight...
As long as you're the minimum away from the person facing you, and you focus on the eyes, You can use whatever aperture you want?
It makes sense, but I cant seem to be able to do it.
For example, this was taken at 1.8 in a low light room... and it is blurry as heck.
How can you make sure it is focused on the eyes?[/QUOTE]


The attached picture is very good. The butterfly is sharp and you focus on the butterfly which I would too but I would use at least f/8 or f/11 to get the faces in decent sharpness. Didn't you have enough light to use a smaller aperture like f/8?[/QUOTE]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

 

[vintagesnaps]

I think the question is more, what is the subject? - the girl, the butterfly, or both? and figuring out an aperture you need to get the entire subject in focus. This looks like mixed lighting if you were in a somewhat dark indoor room with the bright window behind the subject.

Obviously you needed a smaller aperture than what you used to get her face and the butterfly both in focus from this vantage point. To me it looks like the lens may have been more open than needed (too large an aperture); once she moved away from the window into the room then probably opening up the lens more could have worked.

When I have light coming from the background I often aim the camera downward toward the subject; I want to get the meter to read the space in front of me not the light coming in from the background. Then I raise the camera, frame the shot and focus. (I focus manually, that's what works best for me to get the camera focused where I want it to be.)

In a darker indoor area if I couldn't get a camera setting with a smaller aperture due to lower light, I'd probably focus on her face and let the butterfly be out of focus.

I mentioned vantage point because you may want to think about where you stand and which way you're facing. If you'd stepped to the right and been positioned facing her so her eyes and the butterfly were both on the same plane (same distance from your camera) you could have used a larger aperture and probably gotten her and the butterfly both in focus - if you weren't facing into the window. That might have worked better when she was in other darker parts of the room.

If you'd stepped to the left, if you wanted her and the butterfly both in focus you'd probably have needed a smaller aperture, since that would make her farther from the butterfly from that perspective. Then you wouldn't have been shooting directly into the window light so would have needed to meter and adjust shutter speed and ISO as needed to get a proper exposure.

 

[W.Y.Photo]

How to Calculate Depth of Field - Camera Dojo

 

[Buckster]

The attached picture is very good. The butterfly is sharp and you focus on the butterfly which I would too but I would use at least f/8 or f/11 to get the faces in decent sharpness. Didn't you have enough light to use a smaller aperture like f/8?

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Looking at the actual EXIF info of the butterfly shot you posted, your aperture was at f/4 on a 50mm f/1.8 lens on a D3000. With those plugged into a DOF calculator, you can see what your acceptable depth of field to be in focus is, if you have the last piece of information needed, which is the distance from the camera to the subject.

If the distance was, say, 3 feet away, then with that lens on that camera at that aperture, you have about 2" that can be in focus. If the focus is on the butterfly, as it appears to be, what all is going to be in focus is the area from about 1" in front of the butterfly to 1" behind it. Anything out of that range will not be in focus.

If the distance was, say, 4 feet away, then you get about 4" total, 2 inches in front of the butterfly to 2" behind.

If the distance was, say, 5 feet away, then you get about 5.5" total, a little less than 3 inches in front of the butterfly to a little less than 3 inches behind.

And so on.

So then, the question is, how far behind the butterfly is the person you ALSO want to be sharp in the photo? Let's just say, 1 and a half feet. Well then, you've got to first focus on something half way between them in order to figure out the distance you need to be at to get the 3/4 of a foot you need for both to be in focus, which would be pretty much impossible unless you actually HAVE something half way between them to focus on, OR you've got to just deal with the fact that you can focus on the butterfly or the person, and then to get both in focus, you need to be far enough away to get the full 3 feet you need so that everything either in 1.5 feet in front of or behind whatever's focused on is also in focus.

The DOF calculator gives us the answer: You'd need to be about 12.5 feet away to get that full 3 feet of focus range with that lens on that camera at that aperture setting.

Of course, that means that both the person and the butterfly, while both being in focus, will be a lot smaller in the photo.

But if you want to be closer so that your subjects will be larger in the photo, what's the alternative? Close down the aperture to get more depth of field.

At f/8, you'd need to be 9 feet away. At f/11, you'd need to be 7.5 feet away. At f/16, you'd need to be just over 6' away. At f/22, you'd need to be just a little over 5' away.

Of course, you don't have enough light to do that, so NOW what?

You either open up the ISO quite a lot to compensate, which will introduce more noise, enough so that it may look downright horrible when you get home, see it, and realize it's too late to do anything about it, OR you make the shutter longer, which will mean that anything that moves, whether you or the subjects, will blur them, which is also unacceptable.

OR...

You wrap your head around the fact that you need to learn how to use a flash, so that you can get REAL CONTROL over all the other aspects to get the kinds of photo results you want:

1. The lower ISO, for clean, non-noisy photos.
2. The faster shutter speeds, for sharp, non-blurry shots.
3. The smaller aperture, for good depth of field to include everything you want in focus.

 

[astroNikon]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Aperture does not have anything to do with your blurriness, in a direct way

Bluriness is due to your shutter speed being too slow.
You need to increase your shutter speed.
Of course, if you are using the lens wide open at f/1.8 the only way to do that is to ADD LIGHT AND/OR HIGHER ISO !!
OR use a good tripod, assuming the subject does not move.

Out Of Focus from the point of focus would be related to too thin a DOF Depth Of Field, which is related to the f/1.8 Aperture ... if you are taking pictures of people maybe try f/5.6 to f/7.1 --> check a Depth of Field calculator.

If you use a f/5.6 as a guideline
and know your shutter has to be 1/125 for people
then the only variable is LIGHT. which is in the form of
1 - reflecting light onto the front of the subject
2 - adding flash
3 - using higher ISO
4 - using a tripod and a longer shutter speed, which, if the object isn't stationary will generally give a blurry photo.

Getting back to the f/1.8. Many people buy a f/1.8 lens thinking that a miracle will happen. But taking photos at f/1.8 everyone seems to get out of focus pictures .. all due to the shallow depth of field.

Don't get stuck on having a f/1.8 lens for "low light"
Keep learning the basics of ISO <==> Aperture <==> Shutter
Each one has specific contributions to the photo, and you have to learn the limits/flexibility of each.

Sooner or later you'll realize that you have to add light to balance off the other 2 parameters.

 

[Buckster]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Aperture does not have anything to do with your blurriness, in a direct way

Slight correction: Aperture does not have anything to do with MOTION blur, in a direct way.

The non-sharp out of focus areas outside the DOF range are indeed "blurry".

 

[Braineack]

the photo isn't blurry--the butterfly is in perfect sharp focus.

the problem is simply not enough DOF.

I can shoot at f/11 and still not get 1 complete face in focus let alone 2 on different planes.

 

[astroNikon]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Aperture does not have anything to do with your blurriness, in a direct way

Slight correction: Aperture does not have anything to do with MOTION blur, in a direct way.

The non-sharp out of focus areas outside the DOF range are indeed "blurry".

I was trying to make a description distinction for the OP
of the difference of DOF OOF due to Aperture -- versus -- Blurry due to camera/subject movement due to Shutter Speed.

 

[Buckster]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Aperture does not have anything to do with your blurriness, in a direct way

Slight correction: Aperture does not have anything to do with MOTION blur, in a direct way.

The non-sharp out of focus areas outside the DOF range are indeed "blurry".

I was trying to make a description distinction for the OP
of the difference of DOF OOF due to Aperture -- versus -- Blurry due to camera/subject movement due to Shutter Speed.

I understood, but I just thought it might be helpful to the OP to clarify.

There are many kinds of blur. Out of focus areas due to the restrictions of aperture and distance to subject on specific lenses and cameras (commonly abbreviated: OOF), and also commonly referred to as "Bokeh" {which can also refer to the actual quality of the out OOF areas) are most certainly blurry. This can be because of uncontrollable limitations due to light and aperture restrictions, or intentionally used, such as to blur a background to better isolate the subject.

Motion blur can be by accident due to slow shutter speeds, for example, or on purpose, like when panning a moving thing so that the background and other objects blur while the panned object stays relatively in focus, denoting speed of the moving object.

Zoom or spin blur is used usually to create tension and/or draw more attention to a subject in the middle of the shot by zooming the lens or twisting the camera in a quick motion while the shutter is open.

Tilt/Shift blur is often used to make an artificially small depth of field on landscapes in order to make them look like small models. This can be done using an actual tilt/shift lens, which are somewhat expensive, a bellows type camera (rarely used these days except by hard-core large format film shooters), or in post processing using artificial blurs, which is most often the case these days.

Soft focus blur can be by accident just by not properly achieving a good focus with the lens, or on purpose to intentionally create a soft portrait, commonly used in wedding or engagement photography, kittens, babies and other things that can benefit from such soft treatment. (In the old days, we would sometimes even put vaseline on the lens to achieve such effects.

Artificial focus is introduced during post process, and might be used to intentionally achieve any of the effects above, but in a more controlled way. Gaussian blur is a common one that's been around for a long time. Other, more controlled artificial blurs are now available in newer versions of software.

There may be other types of blurs, but those are the first that come to mind, and probably the most common.

 

[Bebulamar]

I did an estimate calculation based on the size of the face. I think the butterfly is about 28 inches from the camera and the faces are about 35 inches from the camera. At 28 inches with the 50mm lens at f/4 and on a DX camera DOF is only a little over an inch. At such a distance even f/16 would not make it either.
May be I should answer the OP this way that the faces and the butterfly must be no more than 1/2 inch apart for both to be in focus.

 

[madisonofriel]

No, It was a very dark butterfly room... I would have used f/8 as I do when I have enough light but this is what I bought the lens for you see.

Aperture does not have anything to do with your blurriness, in a direct way

Bluriness is due to your shutter speed being too slow.
You need to increase your shutter speed.
Of course, if you are using the lens wide open at f/1.8 the only way to do that is to ADD LIGHT AND/OR HIGHER ISO !!
OR use a good tripod, assuming the subject does not move.

Out Of Focus from the point of focus would be related to too thin a DOF Depth Of Field, which is related to the f/1.8 Aperture ... if you are taking pictures of people maybe try f/5.6 to f/7.1 --> check a Depth of Field calculator.

If you use a f/5.6 as a guideline
and know your shutter has to be 1/125 for people
then the only variable is LIGHT. which is in the form of
1 - reflecting light onto the front of the subject
2 - adding flash
3 - using higher ISO
4 - using a tripod and a longer shutter speed, which, if the object isn't stationary will generally give a blurry photo.

Getting back to the f/1.8. Many people buy a f/1.8 lens thinking that a miracle will happen. But taking photos at f/1.8 everyone seems to get out of focus pictures .. all due to the shallow depth of field.

Don't get stuck on having a f/1.8 lens for "low light"
Keep learning the basics of ISO <==> Aperture <==> Shutter
Each one has specific contributions to the photo, and you have to learn the limits/flexibility of each.

Sooner or later you'll realize that you have to add light to balance off the other 2 parameters.

Yes thank you none of this is new to me... I know the basics and I have a tripod and wireless remote, "I already realize" That I need flash. my problem is I can't afford lighting equipment at them moment. I'd LOVE to but Its just not possible for me to spend $200+ on flash. So for now, I have to deal with what I've got.

 

[Buckster]

"I already realize" That I need flash. my problem is I can't afford lighting equipment at them moment. I'd LOVE to but Its just not possible for me to spend $200+ on flash. So for now, I have to deal with what I've got.

You don't need to spend $200. You can get a Yongnuo flash on Ebay for as little as $50 or less.

There's also the flash built into your D3000 camera, which wouldn't cost you a penny to use.