Arpreture.

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After a few months of playing with my new DSLR I have ran into a little bit of confusion.

I was under the impression that shooting, at say, f11, I would be capturing a shot in full detail. But alas some of my pictures are coming out blurred in the foreground and sharp in the background. Is there a general rule that covers landscape and close up shoots when it comes to arpreture? Perhaps this is where I am going wrong?

To redifine what I am saying is that I basically thought at around f2.8 the foreground would be sharp and the background blurred, and at around f18 the whole picture would be sharp.

Sorry for such an amature question but your help will be greatly appreciated, thankyou.
 
'aperture'

shooting at say, f11 or f13, you will need to focus 1/3 of the way into the shot to have a decent balance of focus. this rule applies to landscapes. portraits, you need to focus on your subject :)
 
try this

http://www.mir.SPAM/rb/photography/fototech/htmls/depth.html
 
Delete said:
After a few months of playing with my new DSLR I have ran into a little bit of confusion.

I was under the impression that shooting, at say, f11, I would be capturing a shot in full detail. But alas some of my pictures are coming out blurred in the foreground and sharp in the background. Is there a general rule that covers landscape and close up shoots when it comes to arpreture? Perhaps this is where I am going wrong?

To redifine what I am saying is that I basically thought at around f2.8 the foreground would be sharp and the background blurred, and at around f18 the whole picture would be sharp.

Sorry for such an amature question but your help will be greatly appreciated, thankyou.
Click to expand...


You've got it right. You're talking about depth of field.

In general scenic photography at f/2.8 there will usually be some parts of the picture, in front of and behind the spot on which you're focused, that will not be sharp. You can use this effect creatively.

But if you want everything in the picture sharp, f/18 would usually do it. Not when you're very close, like shooting a flower or something, when depth of field is a lot less, but generally the whole picture should be sharp.

If it's not, then you're probably suffering from camera shake - the shutter speed is too long for you to hand-hold the camera steady and whole picture is blurred. This is quite likely if you're setting the lens aperture to f/18.

Post a pic - it's usually quite easy to tell.
 
foggy4ever said:
try this

http://www.mir.SPAM/rb/photography/fototech/htmls/depth.html
Click to expand...


I have a collection of links to things to help when people ask about stuff, this is a particularly good one for dof. :) thanks.
 
You don't give us much to go on, but higher f-numbers also increase the time the shutter's open, increasing camera shake problems. A rule of thumb is that, holding a 50mm lens, not to expose for longer than 1/50th of a second. Adjust for focal length accordingly, use a tripod or steady some other way.

Also diffraction comes into play. You mention f18 - using an APS-C sensor myself, I would be reluctant to go that high, and tend to stop at f11 or f16 (taking a shot at each) when I want a deep depth of field.

http://www.bobatkins.com/photography/technical/diffraction.html
 
Strolls said:
You don't give us much to go on, but larger apertures also increase the time the shutter's open, increasing camera shake problems. A rule of thumb is that, holding a 50mm lens, not to expose for longer than 1/50th of a second. Adjust for focal length accordingly, use a tripod or steady some other way.

Also diffraction comes into play. You mention f18 - using an APS-C sensor myself, I would be reluctant to go that high, and tend to stop at f11 or f16 (taking a shot at each) when I want a deep depth of field.

http://www.bobatkins.com/photography/technical/diffraction.html
Click to expand...

Please read your opening statement again. :bonk:
 
Apart from the effects of shutter speed, you are referring to the depth of field. This is the distance in front and behind the particular focus distance. It shrinks with a wide aperture (small f-number) and grows with a narrow aperture (large f-number).

You need to research hyperfocal distance.
 
It should also be mentioned that a wide angle lens will have a greater depth of field than a telephoto lens set to the same f-stop.
 
Delete said:
After a few months of playing with my new DSLR I have ran into a little bit of confusion.

I was under the impression that shooting, at say, f11, I would be capturing a shot in full detail. But alas some of my pictures are coming out blurred in the foreground and sharp in the background. Is there a general rule that covers landscape and close up shoots when it comes to arpreture? Perhaps this is where I am going wrong?
Click to expand...

Its aperture not arperture. If something is blured in the foreground and sharp in the background it is not a camera shake issue, like some people have suggested, as everything would be blury.

Delete said:
To redifine what I am saying is that I basically thought at around f2.8 the foreground would be sharp and the background blurred, and at around f18 the whole picture would be sharp.

Sorry for such an amature question but your help will be greatly appreciated, thankyou.
Click to expand...

At f18 you will get a much larger depth of field compared to f2.8 however depth of field ranges forwards and backwards from where you focus. Trying to indicate this in a diagram below might be easier

the focus point is | and the limit of things in focus are defined by < and >

---------<-|->--------- this is typical at f2.8
------<----|---->------ this might be f8
--<--------|-------->-- this might be f18 still focusing part way into the scene

<--|-------->---------- this might be f18 focusing a long way back leaving a lot of foreground out of focus


This is a very simplified diagram, in reality focus behind extends more than focus in front but as a quick doodle I think it demonstrates the point.

louise-knight said about focusing 1/3 of the way into the picture - this is a very lose guide based upon the rear focus extending further than front but is not true the majority of the time. Follow andrewc's advice and read more about hyperfocal distance (Lee Frost covers this in his landscape book)
 
oldfella said:
Please read your opening statement again. :bonk:
Click to expand...

I think Strolls knows what he means, but it's always ambiguous when you use the words larger, bigger, wider, higher in connection with apertures and f/numbers. How about brighter and darker?
 
I knew I had spelt it wrong but didnt have the energy to go and find the correct way of spelling it lol.


Thankyou for everyones imput, you have answered a few questions that had me perplexed at times. Ill get a few pictures and post them up so you guys can tell me what I should be doing.

Oh yeah, and thanks for the diagram, I'll also get me a copy of that book.
 
Just to put a little spanner in the works of what people are saying about DOF...

You need to have an idea of how much DOF you actually need... with a 28mm lens focused at say a foreground object 3m away, f11 will achieve the sharpness you require from front to back... It's rare you will ever need to use much more than f11 in a general landscape shot... and if you dont need it dont use it for two reasons... the first is that your shutter speed is slowed down giving more oportunity for the effects of camera shake... and the other is that your lens will have a sweet spot where it just naturally produces sharper images at a certain f no than the rest due to distortions... this is generally between f8 and f13 for lenses...the efect of DOF is more for closer up feects say 0-3m away from your camera... portrate and still life photographers really need to know there DOF...

The best thing you could do is go to the on line dof calculator... google it and you will soon find it... put in your lens and camera in and produce tables for yourself and your lenses... laminate them and take them out with you... consult them and use them and you soon will get to grips with it... the tables will also show what im on about in terms of at f11 giving you often more than enough DOF for landscape needs...
 
Don't know if it's been said but there's a nice section in 'Understanding Exposure' that I like to reference.

Basically, think of your camera's sensor as a bucket, your lens as a funnel, and light as a tin of paint.

At f/2.8, it's a SMALL f number, but a WIDE aperture.
At f/22, it's a BIG f number, but a NARROW aperture.

At f/2.8, the bucket has no funnel
At f/22, the bucket is using a fine funnel.

So, at f/22, you're pouring your paint through a fine funnel. You're making absolutely no mess, and the paint is filling into the bucket really slow and gently.
This basically equates to having a maximum depth of field, but it takes ages for the light to get into the lens because of the small hole in the lens.

At f/2.8, you've got no funnel. You tip the tin of paint upside down, and the paint launches into the bucket in a split second. Paint is flicked all up the edges of the bucket and some has come out of the bucket, but hey, you got it in the bucket quickly!
This equates to a really narrow depth of field - you've got paint EVERYWHERE, but the small amount of paint in the bucket is the sharp bit of a picture. Plus, the light got into the camera super quick.
 
foodpoison said:
Don't know if it's been said but there's a nice section in 'Understanding Exposure' that I like to reference.

Basically, think of your camera's sensor as a bucket, your lens as a funnel, and light as a tin of paint.

At f/2.8, it's a SMALL f number, but a WIDE aperture.
At f/22, it's a BIG f number, but a NARROW aperture.

At f/2.8, the bucket has no funnel
At f/22, the bucket is using a fine funnel.

So, at f/22, you're pouring your paint through a fine funnel. You're making absolutely no mess, and the paint is filling into the bucket really slow and gently.
This basically equates to having a maximum depth of field, but it takes ages for the light to get into the lens because of the small hole in the lens.

At f/2.8, you've got no funnel. You tip the tin of paint upside down, and the paint launches into the bucket in a split second. Paint is flicked all up the edges of the bucket and some has come out of the bucket, but hey, you got it in the bucket quickly!
This equates to a really narrow depth of field - you've got paint EVERYWHERE, but the small amount of paint in the bucket is the sharp bit of a picture. Plus, the light got into the camera super quick.
Click to expand...

Got to say that is the most bizarre and least helpful explanation of depth of field I've heard. Bucket, funnel and paint everywhere means shallow depth of field? What?! The things people dream up to sell books :shake:
 
I've heard similar analogies to describe how aperture and shutter speed work - using the flow of water through different size hosepipes, but not expanded to illustrate DOF. I think that is one step too far.
 
HoppyUK said:
Got to say that is the most bizarre and least helpful explanation of depth of field I've heard. Bucket, funnel and paint everywhere means shallow depth of field? What?! The things people dream up to sell books :shake:
Click to expand...
It does make complete sense if you consider the time taken to fill the bucket.

I'm not so sure about the "mess everywhere" part - we're all familiar (??) with the concept of using a wide aperture (low f-number) to keep the subject in focus and the background blurry. Typically we associate this with a very sharp subject.

Stroller.
 
Strolls said:
It does make complete sense if you consider the time taken to fill the bucket.

I'm not so sure about the "mess everywhere" part - we're all familiar (??) with the concept of using a wide aperture (low f-number) to keep the subject in focus and the background blurry. Typically we associate this with a very sharp subject.

Stroller.
Click to expand...

I beg to differ. It's a misleading half truth. 'Time' has no direct effect on depth of field, any more than ISO has ;)
 
HoppyUK said:
I beg to differ. It's a misleading half truth. 'Time' has no direct effect on depth of field, any more than ISO has ;)
Click to expand...
Well, I didn't take it as a metaphor for depth-of-field. I took it as a metaphor for aperture versus exposure time.

I would use this metaphor for avoiding camera shake - you don't want to take too long to "fill the bucket" therefore you use a bigger funnel.

All metaphors have limitations, and if you extend any metaphor too far it'll become "a misleading half truth". That's why metaphors are best used within the context of a fuller explanation.

Stroller.
 
Strolls said:
Well, I didn't take it as a metaphor for depth-of-field. I took it as a metaphor for aperture versus exposure time.

I would use this metaphor for avoiding camera shake - you don't want to take too long to "fill the bucket" therefore you use a bigger funnel.

All metaphors have limitations, and if you extend any metaphor too far it'll become "a misleading half truth". That's why metaphors are best used within the context of a fuller explanation.

Stroller.
Click to expand...

That's interesting; I took it to be about depth of field!

Good analogies and metaphors should not become misleading half truths, that's why they're helpful I think.

For example, here is a variation of the popular filling-a-bucket-with-water analogy for correct exposure which I think stands up to close examination. It covers the interaction of shutter speed, lens aperture and ISO, with different light levels.

Post #20 http://www.talkphotography.co.uk/forums/showthread.php?p=1175185#post1175185

But it does not attempt to address depth of field (or camera shake!) because they are not directly related to exposure. While these are obviously very important considerations, and indirectly related much of the time, they are separate, and in order to get a good understanding purely of exposure it is important to know that.

Anyway, I hope it's helpful :)
 
Crikey, I feel like I've walked onto a minefield lol

I'm going to sit and read the links you guys have posted up, thankyou very much for your time explaining things.
 
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