Beginner Where to focus and when to use hyperfocal distance

Oatcake

Oatcake

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Matt
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Hi all,

I’ve read a LOT about focusing and how to do it, all of which I understand, but I can’t seem to find a useful guide about when to use a particular focusing method and where to place your point of focus. If there’s a key focus point in the image if just been placing my autofocus target on that, but in other scenes that are more busy (especially woodland scenes) I struggle to identify a specific point of focus and end up just focusing a third of the way into the scene, or attempting to use hyperfocal distance.

Hyperfocal distance seemed to render the foreground elements slightly OOF. Is it just a decision you have to make at the time? Focus on the foreground elements and lose definition in the background, or use hyperfocal and lose some definition in the foreground? What type of shot/composition makes a good candidate for hyperfocal distance? The other thing I find difficult with hyperfocal distance is that the calculator tells me to focus at 1.91m and the focus scale on my camera is in increments much larger than that.

Any help/advice would be much appreciated.

Matt
 
If the chart is telling you 1.91m, "about 2m/6'" is pretty close (if you're wondering what difference it makes, re-run the DOF calculators for 1.8m and 2.2m). You can gauge something about 2m away and spot focus on that.

Hyperfocal is for when you want to optimise the focus throughout the scene and all the way to the horizon. It's easier with a wider lens. But you need to always think about what you want to achieve with your focus - do you need the image sharp to the horizon or are you wanting to draw attention to part of the scene through your focussing?

How about some sample shots where you've struggled to get the depth of field that you want? - it's always easier to discuss specific examples.
 
Until recently was using a 12mp Fujifilm X10 and with it's low resolution focussing wasn't really a problem. Since moving to the 36mp Sony A7R, I have found focusing to be much more critical.

The other thing I can't understand is the DOF calculator android app I'm using has a 'subject distance' field that seems to have a big effect on the DOF. If I'm using hyperfocal, what value would I put in this box to maximise focus across the entire scene when there is no apparent focus for the composition, like some of the wide vistas below?

Here are a couple of my shots. Where should I be focussing in these? And what apertures should I be using?


Woodland Walk 2 by Matthew Martin, on Flickr


The Love Tree by Matthew Martin, on Flickr


Road to Nowhere by Matthew Martin, on Flickr


Dune, Newborough by Matthew Martin, on Flickr


Newborough, Anglesey by Matthew Martin, on Flickr
 
There's usually a fairly obvious point of interest in a shot, for example the people on the beach of the gnarly roots in the Love Tree. I would make sure that the main point of interest was in sharp focus then use f/8 or f/11 to get sufficient DoF (or shoot wide open to get as shallow a DoF as possible) for the rest of the scene. As Alastair said, don't get too hung up on exact measurements - DoF is fairly subjective anyway, it's more like the area of acceptable sharpness than the range of absolute sharpness!
 
Oatcake said:
Until recently was using a 12mp Fujifilm X10 and with it's low resolution focussing wasn't really a problem. Since moving to the 36mp Sony A7R, I have found focusing to be much more critical.

The other thing I can't understand is the DOF calculator android app I'm using has a 'subject distance' field that seems to have a big effect on the DOF. If I'm using hyperfocal, what value would I put in this box to maximise focus across the entire scene when there is no apparent focus for the composition, like some of the wide vistas below?
Click to expand...
It's the small sensor vs. big sensor issue (physical size, not megapickles). The smaller sensor in the X10 effectively gives a greater depth of field than the full-frame in the A7R when you frame the shot to capture the same scene. I'm over-simplifying but you can find long and argumentative threads elsewhere on the forum discussing this with less clarity.

What the app is calling "subject distance" sounds like it's means the distance to which you set your focus.

Your depth of field is a function of:
  • Physical sensor size - larger sensor means less of the scene in focus (gross over-simplification, but before the usual wingnuts jump on this statement remember we're in Talk Beginners)
  • Focal length - wider lenses can capture a greater depth of focus than longer lenses
  • Aperture - closing up the aperture increases depth of focus but be aware of the diffraction demons (there is no practical reason to ever go beyond f/16, better to hold at f/11)
  • Point of focus - for any given point of focus, you get about 1/3rd the depth of field in front of that point and 2/3rds behind it - this is why your app gives you changing results with changing the "subject distance"
For me seeing using a DOF Table (http://www.dofmaster.com/doftable.html) makes more sense than an app, because you can see the effects of changing parameters in parallel.


You won't always get full depth of field throughout an image - in most cases it wouldn't be that interesting if you could. You need to prioritise where you draw the viewers attention to. Usually the foreground has more significance than the horizon, so you'll let the distance go and keep the foreground sharp.

In your examples, the two woodland shots I'd make sure the tree in the near-ground was in focus and let the distance drift out of focus. Similar with the first dune shot. With the wider beach shot I might let the foreground fall out of focus and keep the horizon in-focus to draw the eye through the image (there's bugger all interest in the immediate foreground, it gets interesting from the middle-ground onwards).
 
Thanks for the feedback guys.

Say I use the table that Alastair linked to and let's say I'm shooting the love tree shot again. If we say the tree is 4m away (I'm assuming I can only estimate this?) and I'm using a focal length of 44mm and f/8.0 that gives me a DOF of 2.68-7.85m, if I spot focus on the tree? Is that right? The DOF table reports a hyperfocal distance of 8.11, so does that mean I should manually focus to 8.11 to get the maximum DOF? What would the DOF actually be in terms of metres if I were to focus at that distance?
 
If you focused at 8.11m your depth of acceptable focus would be (roughly) from four-and-a-bit metres from the camera to infinity. So not that great for a tree that you guess is 4m from the camera.


However, with the tree about 4m away, if you stopped down to f/11 and focused about 6m into the scene (maybe that slightly smaller tree to the right) your acceptable focus is now from less-than-three metres to infinity.

Or for another approach, set the aperture to f/5.6 and focusing on the tree (4m-ish) gives you from 3m to 6m in focus and you're pulling attention to the tree and allowing the foreground and the background to drop out of focus. It's quite a busy background with all those leaves, so losing a bit of sharpness there won't hurt if you want to draw the attention to the trunk.
 
Ah ok, I see.

So in terms of when to use what method, would it be fair to say that when there's nothing of interest in the immediate foreground then hyperfocal distance is a good way to go. Otherwise it's better to just spot focus on the subject of interest and move aperture down or up depending on the desired DOF?
 
It's photography, it's an art, there are no hard and fast rules.. ;)
 
I understand that, but I also know there's a lot of sh*t art flying around the interweb, and I don't want any of it to be mine ;)

I guess I was looking for the 'rule of thumb'.
 
I've never got on with hyperfocal focusing, I tend to work to two workflows when I am out shooting

1) Focus manually in live view (at 100% magnification) and decided what is the more important thing to have in critical focus - the background or the foreground. Once I've done this, I'll focus to whichever I've decided and then check to see how the focus in the rest of the frame is. With a wide lens, and a small aperture, I'll focus manually so the background has just turned sharp (enough) which will render pretty much everything else in focus.

2) Take two shots with one focussed for foreground and one for background and combine in Photoshop. This doesn't work so well on lenses which display a large amount of focus breathing - my 16-35 is a nightmare for this.
 
The problem with using hyperfocal focussing is that It does not place the point of maximum focus where you want it.
What is gives you is a range of "Acceptable" focus when set to a suggested distance. Focus actually falls off from its maximum, each side, of that focus point.
 
stumeech said:
2) Take two shots with one focussed for foreground and one for background and combine in Photoshop. This doesn't work so well on lenses which display a large amount of focus breathing - my 16-35 is a nightmare for this.
Click to expand...

Funny you should mention that. I was going to try focus stacking. I guess this is a form of that (I haven't worked out an easy way to calculate what focus distances to use to ensure I capture the full DOF yet). Wouldn't auto-aligning the layers in PS solve the focus breathing issue?

Thanks for the tips, I think I'll try both of these methods on my next shoot.
 
Oatcake said:
Funny you should mention that. I was going to try focus stacking. I guess this is a form of that (I haven't worked out an easy way to calculate what focus distances to use to ensure I capture the full DOF yet). Wouldn't auto-aligning the layers in PS solve the focus breathing issue?

Thanks for the tips, I think I'll try both of these methods on my next shoot.
Click to expand...
Using this shot below as an example

470b45b40bfd80d0d69d02f6f32f9974


I found Photoshop just couldn't align all features sufficiently as there is so much focus breathing at f/11, so I just merged the three layers by hand.

Incidentally, the shot below is an example of when I used method 1 for focussing landscapes in the field:


Tulip Field by Stu Meech, on Flickr

I made sure the church in the background was just sharp enough (as it isn't the most important feature in the shot) and this rendered all those tulips inches from my front element sharp.
 
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Thanks for the examples Stu, that helps a lot. I'm a big fan of blending by hand actually so it's good to know that's an option too.
 
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