How to increase focus area?

[dennison]

Hey everyone! I have a newbie question. How do you increase the focus area?

In my example shot (see http://blog.codesignstudios.com/wp-c...8/10/Feast.jpg), only a small area is in focus. Some ants above and below the cockroach are blurred out, and the ones at the top left far end are barely recognizable. Is it possible for me to replicate this same scene with all ants in focus, maybe including the ones at the top left?

I apologize if this has been asked before (I did use the search function but came up empty).

[Not4wood]

Originally Posted by dennison

Hey everyone! I have a newbie question. How do you increase the focus area?

In my example shot (see http://blog.codesignstudios.com/wp-c...8/10/Feast.jpg), only a small area is in focus. Some ants above and below the cockroach are blurred out, and the ones at the top left far end are barely recognizable. Is it possible for me to replicate this same scene with all ants in focus, maybe including the ones at the top left?

I apologize if this has been asked before (I did use the search function but came up empty).

Hey and Welcome to the Camel.
Now, as far as DOF or what is known as Depth of Field it all depends on your subject to camera distance as well as the focal length of the lens. What your basically doing is your going to try and close down or make your Aperature smaller to increase the DOF but if your very close as in shooting Ants you wont really have much of a change. Go here for an Online DOF Calculator: Online Depth of Field Calculator

[blumesan]

First, WELCOME TO THE CAMEL.
Second, the link to photo doesn't work.
Third, it would help to know the type of camera, lens and aperture used.

Cheers/Mike

[Take12]

Fourth, all shall be revealed here.

[dennison]

Thank you to all who responded. I am slowly getting there. I am a bit confused by this statement (taken from the wikipedia link)

For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.

So let's say I am trying to take a landscape photo from the top of a mountain, to get the entire scene should I decrease magnification by pulling my lens all the way down (e.g. 18 mm) and put the f-number all the way up (e.g. f/22)?

For my sample photo please try this link:

[korman]

Originally Posted by dennison

So let's say I am trying to take a landscape photo from the top of a mountain, to get the entire scene should I decrease magnification by pulling my lens all the way down (e.g. 18 mm) and put the f-number all the way up (e.g. f/22)?

Welcome here with your second question.

First, the magnification doesn't play any role here, focussing works all the time. On top of your mountain, you'd best choose the focal length that put the stuff on the picture you want to have there. You are correct about shorter focal lengths put more into the image, but the stuff ends up smaller.

Now about the f-number, it has nothing to do at all with magnification. For each f-stop, there's a distance from which on everything is in focus. That's called hyperfocal distance. So if the nearest object you care about is far enough away, any f-stop will give you a nice landscape image.

Korman

[dennison]

Originally Posted by korman

Welcome here with your second question.

First, the magnification doesn't play any role here, focussing works all the time. On top of your mountain, you'd best choose the focal length that put the stuff on the picture you want to have there. You are correct about shorter focal lengths put more into the image, but the stuff ends up smaller.

Now about the f-number, it has nothing to do at all with magnification. For each f-stop, there's a distance from which on everything is in focus. That's called hyperfocal distance. So if the nearest object you care about is far enough away, any f-stop will give you a nice landscape image.

Korman

Thanks for the response, Korman! I am having trouble focusing to infinity, probably due to lack of experience and/or knowledge. Maybe I still have to develop my eye for it. Do all lenses have the capability to focus to infinity? I noticed that both my lenses have this strange, alien marking with the infinity symbol (see attached photo).

What does this mean? What is that o symbol with the forward slash?

[Finn]

The "sideways 8" symbol is the symbol for infinity, in that picture it simply means your lens will focus from infinity down to a minimum focus distance of 0.28m or 0.92 ft. So anything closer than 28cm you be unable to focus on.

You can get some specialised macro lenses which dont focus to infinity they might only focus for a few cm just in front of the lens as thats all you would need for macro.

[korman]

Originally Posted by dennison

I am having trouble focusing to infinity,[...]

Usually you don't focus on infinity as it's rather hard to capture anything at infinite distance.

Just focus on the first thing you want to have in focus and, if that's far enough away for the selected t-stop, everything as far as you can see behind it will be in focus too.

Korman

[highbarger]

Ooops! Double post.

[highbarger]

Originally Posted by dennison

What is that o symbol with the forward slash?

That indicates the diameter of the filters that your lens accepts, in this case 52mm.

[dennison]

Wow I'm learning so much. You guys are awesome! Thank you for the responses. I really appreciate it. Hope I can contribute something back some time.

[Take12]

Originally Posted by dennison

I am having trouble focusing to infinity, probably due to lack of experience and/or knowledge.

What do you mean "I am having trouble focusing to infinity"?
You mean you can't see if infinity is in focus (as with landscapes)? Then adjust your diopter (and maybe go see an optician?).
Or do you mean your lens will not focus to infinity? Then send it in for repair.

Do all lenses have the capability to focus to infinity?

All do, except a few specialised macro lenses.

[kris142]

Michaels Photography School Home

[JohnC]

Magnification is the key to depth of field calculations. That was insightful for you to pick that up so quickly. If the subjects image size on the camera's sensor is the same size the DOF will be the same, even if you have two very different focal length lenses.

That is why we're always told that you get more DOF with a shorter lens. It is because the shorter lens magnifies the subject less. What this statement depends on (but what is often left out of that instruction) is that the camera has to be the same distance away from the subject giving you a smaller subject. If you frame a flower with a 100mm lens and then change to a 24mm lens WITHOUT MOVING THE CAMERA you will have more DOF with the 24mm lens. However, if you move in closer with the 24mm lens so that the flower is framed the same as it was with the 100mm lens the DOF will be the same.

Magnification and aperture are the controls we have over Depth of Field. Focal length is not part of the DOF equation.

Here are more good references:
Depth of field and diffraction
DOF Revisited
Depth of field

[Mechoption]

Originally Posted by JohnC

Magnification and aperture are the controls we have over Depth of Field. Focal length is not part of the DOF equation.]

I'm confused, aren't magnification and focal length two different ways of saying the same thing? If focal length is not a part of the DOF equation, why is it needed by the DOF calculator? Online Depth of Field Calculator

[blumesan]

Magnification, focal length and focal (object) distance are three inter-related variables. Given any two, the third is fixed. Thus in any DOF calculation only two of these variables must be specified. A proper DOF calculator will allow you to input just the magnification, object distance and aperture; and it will calculate the focal length required.

[Rense]

Here is a video that shows it all.

[Loa]

Originally Posted by blumesan

Magnification, focal length and focal (object) distance are three inter-related variables.

Ha! And pixel density, of course!


Loa

[blumesan]

Originally Posted by Loa

Ha! And pixel density, of course!
Loa

Yes, pixel density of course.

But, for all its virtues, it has no effect on DOF.