Focus - f/1.8 at Distance

[BarryG]

Maybe a silly question, but if I am shooting at 1.8 close range I know the focal point is tiny.

Is that the same if the subject is say, 10 feet away?

 

[Gary Coyle]

Maybe a silly question, but if I am shooting at 1.8 close range I know the focal point is tiny.

Is that the same if the subject is say, 10 feet away?

If you mean is the depth of field the same then no it isnt, google depth of field calculator

 

[BarryG]

No, not depth of field, but rather would the focal point be larger?

Maybe that's the same thing thinking about it.

 

[Russ77]

No, not depth of field, but rather would the focal point be larger?

Maybe that's the same thing thinking about it.

Let's say you were taking a photo of a teddy bear (first thing that sprang to mind) and took a shot from 3ft focusing on it's nose, then took a shot from further away but still focused on it's nose, there would be more depth of field in the second shot but the focal point remains the same.

By more depth of field we mean that there is more appears to be in focus behind and in front of the focal point.

 

[corbystock]

Just an example - say you were taking a photo of someone's face at f/1.8, close up you could have the eyes in focus but the nose & ears out of focus - the further you move back or zoom back the ears & nose will become in focus & so on.

 

[AboveFunction]

No, not depth of field, but rather would the focal point be larger?

Maybe that's the same thing thinking about it.

The focus point (if that is what you mean) stays the same size but the further you are away the smaller the subject will be smaller allowing you to focus on more.

 

[HoppyUK]

Depth of field is changed by f/number, focal length, and distance. Also by the size of the camera sensor.

Good DoF calculator here http://www.dofmaster.com/dofjs.html

 

[BarryG]

Question answered, thanks fellas.

So if I am doing a bit of street photography and the light is terrible, I can go down to f/4 or something and pretty much get someone in focus at 10ft of so.

Great.

 

[inaneredstripe]

you can focus on them at whatever distance from the camera. but the amount , rear to front, that is in sharp focus, will differ.

 

[inaneredstripe]

just up your ISO.

 

[BarryG]

just up your ISO.

I do play with the ISO, but on the D200 I am limited in what it can do.

 

[Forbiddenbiker]

Question answered, thanks fellas.

So if I am doing a bit of street photography and the light is terrible, I can go down to f/4 or something and pretty much get someone in focus at 10ft of so.

Great.

It does depend on what lens your using. A 50mm will give you about 2 feet of sharp depth of field, where as a 30mm will give you more than twice that.

Which also equates to the 30mm at f2.8 giving you a similar DoF as the 50mm at f4.

Then also, the bonus of using a wider lens means one can make use of the wider field of view, which aids the ‘in focus’ appearance of the out of focus areas either side of the DoF range .. in effect making them appearing nearly as sharp. .. which in turn extends the apparent visual sharpness of the oof areas and the whole shot when viewed normally.

Hope that makes sence. .