Hyperfocal Distance and Depth of Field

[alex]

Okay, so I really enjoy landscape photography, it's pretty much my biggest area of interest. I've only had a dSLR now for just shy of two months, so I'm just starting to understand the use of the aperture for depth of field, obviously something that is very important in landscape photography.


With my previous camera (S2 IS), I really never used anything but the Program mode, and never took the time to really understand what Av and Tv really were for, other than to use for long exposures at night.


So now I learn about this thing called hyperfocal distance. I understand that even with landscapes, I'm not always going to want to have everything in the frame in focus. But obviously a good bit of the time, I will. Not a problem, just get a hyperfocal distance table to find out what the distance is for whatever aperture and focal length you are using.


But then what? How on earth do I really know if the spot I'm focusing on is 16ft from the sensor? There aren't any distance markings on my lens (17-55mm f/2.8) other than the little tiny distance window on the top that gives about 4 numbers between 1.2ft and infinity. Are you really supposed to guesstimate when trying to utilize hyperfocal distance?


Or do you just focus for a spot one-third of the way from the bottom of the viewfinder when it's centered on what your final composition is going to be?


Thanks...


alex

[Madison]

PS: I use DOFmaster (if I remember to bring my iPod with me). Check it out because it will do the calculations for you.


Often, open wide, the 17-55 will not be specific and can focus to infinity.


The online version of Dofmaster is here: http://www.dofmaster.com/dofjs.html


The iPhone or iPod Touch version is in the App Store (Apple). And they do one for Palm too I think. It could be handy if you are new to this and require good calculations for hyperfocal stuff.








Other than that I cant help you because I am *just* starting to figure out landscape photography myself. But I did want to mention this utility because it helped me out (I am severely dyscalculic (yes that exists)).

[alex]

thanks for the link, Madison. I printed out a hyperfocal distance chart to carry with me.





Does anyone know how you're supposed to know where "x feet" is in your viewfinder with out detailed distance markings on your lens?

[Daniel Browning]

Most of the solutions to this problem are slow, inaccurate, and/or expensive:

Guesstimate.
DOF preview.
Tape measure.
Expensive lenses with long-throw focus rings and accurate markings.
Live view.



Guesstimate is fast but inaccurate. Compensate for inaccuracy by shooting deeper DOF than needed to cover errors.


DOF preview is the button that stops down the lens to show you what the DOF is like in the viewfinder. It's fast, but inaccurate, as the the resolution of the viewfinder is usually not high enough for large prints (small CoC).


Tape measure is slow, but accurate.


Manual focus lenses built for other formats often have improved focus rings and markings. Cine lenses, in particular, are excellent in this regard, but very expensive. The recent Zeiss lenses released for EF format are better than most autofocus lenses in this area.


The best method is live view. In exposure simulation mode with 10X magnification, you can see exactly what's in focus. Simply put the magnifying glass on infinity and pull the focus ring until just before you start to see infinity lose focus. It's so fast and easy, it makes hyperfocal shooting a breeze, you don't need any charts or math, and there is no error. The only downside is the cost of a new camera that includes the feature.

[electric eel]

It is rare for a zoom lens to have any depth of field markings that will be worthwhile, Nikon used to provide these on some of their push-pull zooms of 1960-1980's but they were not entirely accurate. Prime lens (especially older lenses) had great depth of field markings with long throw focusing rings so the markings weren't jammed together. Btw- depth of field is 1/3 in front of the focus mark and 2/3 behind, so if you focus at 30' , the depth of field would extend from 20' to 50', this is just a hypothetical example. The cheap solution to this is to purchase some lenses with nice depth of field marks, consider the myriad of older lenses from other manufacturers such as Nikon and Pentax primes and adapt them....they will be sharper than zooms and they'll last a lifetime. I am currently using a Nikon 24mm f2.8 from the early 1970's on a 5D Mk II and the results are superb. Lenses from about 1985 to present changed their optical formulas and there seemed to be a preference for shorter turning distance of the focusing ring, the depth of field markings decreased and were jammed together which makes them less useful, so just be aware of this. Depth of field markings on lenses are optimized for a certain print size, and if memory serves me correctly I believe it is 8x10, therefore is you print larger you need more depth of field, if f8 markings look good you will need to use f11 or f16 instead. Be careful not to stop down too far on a lens because diffraction will occur and your sharpness decreases.....you might now realize why wide-angles are so popular for landscape.....large depth of field at f5.6, 8, these are usually the sharpest aperatures for a f2.8 lens of the older vintage, newer lenses (especially costlier ones) might be sharper by f4. There is lots of discussion about digital sensor depth of field being shallower than film but I'll save that for later or you can inquire.

[Daniel Browning]

Great post, electric eel. One brief comment:



Btw- depth of field is 1/3 in front of the focus mark and 2/3 behind, so if you focus at 30' , the depth of field would extend from 20' to 50', this is just a hypothetical example.


That's true near the hyperfocal distance but for other distances, the DOF can be the other way around (2/3 in front and 1/3 behind), it depends on the specifics.

[Madison]

The best method is live view. In exposure simulation mode with 10X magnification, you can see exactly what's in focus. Simply put the magnifying glass on infinity and pull the focus ring until just before you start to see infinity lose focus. It's so fast and easy, it makes hyperfocal shooting a breeze, you don't need any charts or math, and there is no error. The only downside is the cost of a new camera that includes the feature.
<div style="clear: both;"]</div>








Daniel: thanks for thie simple but effective tip. I am going to experiment with it next week. It's so simple yet I never managed to think of it myself because I still haven't gotten used to the fact that my new camera has live view. So this is great. Thanks!

[electric eel]

Thanks Daniel, I wasn't aware of the switch, I'll definitely want to learn more about that, if you have any examples could you post?

[Daniel Browning]

Sorry, my mistake. It doesn't become the other way around, but it does slowly go from 50/50 out to 1/3, then 1/100:


http://www.dofmaster.com/dofjs.html ("http://www.dofmaster.com/dofjs.html)


With Canon 50D, 55mm focal length, f/16, 11 feet subject distance: 2.74 ft in front of subject (33%, 1/3rd), 5.45 ft behind subject (67%, 2/3rds).

The closer you get to infinity, the more it stretches out behind the subject until it gets to infinity:

32-ft subject distance: 15.8 ft in front of subject (1%), 1231 ft behind subject (99%).


The closer you get, the more it becomes 50/50:


3-ft subject distance: 0.24 ft in front of subject (46%), 0.28 ft behind subject (54%).

[alex]

Thanks for the information, everyone!






The best method is live view. In exposure simulation mode with 10X magnification, you can see exactly what's in focus. Simply put the magnifying glass on infinity and pull the focus ring until just before you start to see infinity lose focus. It's so fast and easy, it makes hyperfocal shooting a breeze, you don't need any charts or math, and there is no error. The only downside is the cost of a new camera that includes the feature.
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With this method, obviously infinity will be in focus, but how do I also make sure the entire foreground is also? I'm still confused.

[Daniel Browning]

With this method, obviously infinity will be in focus, but how do I also make sure the entire foreground is also? I'm still confused.


Start with the f-number that you think will have approximately sufficient depth of field. Then focus using above technique. If the foreground is not within the depth of field, stop down some more and refocus.

[electric eel]

Thanks Daniel, I never paid much attention to the tables but it appears they are valuable, have you ever checked the tables against the depth of field markings on a lens, I wonder how accurate the markings are against the tables? Time to drag the older lenses out and check this.

[Daniel Browning]

...have you ever checked the tables against the depth of field markings on a lens, I wonder how accurate the markings are against the tables?


I haven't, but I would guess that they are accurate.

[alex]

Start with the f-number that you think will have approximately sufficient depth of field. Then focus using above technique. If the foreground is not within the depth of field, stop down some more and refocus.
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Duh. take more than one shot! Thanks again Daniel. I appreciate your advice!

[David Selby]

I created a short little lesson about DOF and hyperfocal distance focusing and its benefits.





it can be found here:





http://www.learnslr.com/slr-beginner-guide/digital-slr-learning-guide/hyperfocal-distance ("http://www.learnslr.com/slr-beginner-guide/digital-slr-learning-guide/hyperfocal-distance)

[Alan]

David, this is a helpful tutorial.


On the second picture (night shot), where did you focus, and was the aperture at f/8?

[David Selby]

Thanks, I focused approximately six feet away on a subject and then recomposed.






<table width="100%" cellspacing="0" id="Inbox"]
<tbody>
<tr>
<td width="30%" style="font-size: 120%;"]Exposure:</td>
<td style="font-size: 120%;"]20 sec (20)</td>
</tr>
<tr>
<td width="30%" style="font-size: 120%;"]Aperture:</td>
<td style="font-size: 120%;"]f/8</td>
</tr>
<tr>
<td width="30%" style="font-size: 120%;"]Focal Length:</td>
<td style="font-size: 120%;"]17 mm</td>
</tr>
<tr>
<td>ISO Speed:</td>
<td>200</td>
</tr>
</tbody>
</table>

[Alan]

Thanks, David.


So, just to be sure I'm understanding what you did, you focused on a subject on the bridge where you were standing, then swung the camera around to recompose the shot, and then took the picture.


Is this correct?

[David Selby]

yes, that is correct.... of course for that shot there wasnt' to much all that "close" to me that I needed to do it but i was testing out the quality of focus and sharpness on something further away like the water fall when I focused only 6 feet away.

[Alan]

David, I'm back with another question about this subject, so bear with me.


In focusing on the subject that is X feet away, did you put your camera to manual focus, then recompose and shoot the water fall picture?


I'm trying to envision a situation where I've got to focus on a subject (for example, in AF mode), move the camera around while keeping the focus locked, trying to keep the landscape properly level, etc., without losing the focus lock. In many cases, I'd be using a remote switch, which further ties up my hands.


Could you elaborate on your technique? Thanks.

[David Selby]

Sure. I use the rear * or AF On button depending on which camera body I'm using to focus. What this means is, I focus on my subject X feet away by pressing the button on the rear of the camera. When I recompose and press the shutter, focus is not affected and does not change unless I pressed the focus button on the rear of the camera.





This makes it easy, and I always shoot with the focus and AE lock/shutter separate from the focus.

[Alan]

Sorry for the late reply, David.


Thanks.


But, the AF button behaves the same as the shutter button. I didn't think the AF button would lock the focus, or am I mistaken on that? I've got a 5D Mk 2.

[David Selby]

Kind of confused here...





I separate the focus function and the shutter function, therefore if i press the shutter half way all I do is meter lock I do not focus via the shutter button at all.


I press the AF button on back of camera, focus, let off the button and recompose and press shutter.

[Alan]

Got it. Thanks.


You aren't confused. I was.