On Depth Of Field and PWT Photos

Discussions on Equipment, Locations and Tips for getting the photograps you want of Vermont scenes.Note: You must be registered in order to post. If you have trouble registering, use the contact us form on Scenes of Vermont's home page.

Moderators: bm, Andy, admin

Andy
Site Admin
Posts: 1493
Joined: Sun Sep 18, 2005 12:01 am
Location: Saginaw, Michigan
Contact:

On Depth Of Field and PWT Photos

Postby Andy » Sat Jun 20, 2009 12:09 pm

On the foliage forum, I got into an off-topic reply to one of PWT's posts and we started talking about DOF. I thought it was more appropriate here.

Depth of Field, in my simple, lay view, is how much of a photographic image is in "sharp" focus (a relative term) from front to back. The optics of a lens limits this.

Generally, two "adjustments" on a DSLR/SLR body/lens combination will affect DOF. The first is the focal length of the lens, and the second is the size of the opening (aperture). The following are generalities (there are specially designed lenses and a more scientific approach to all of this):

Longer focal length lenses at the same distance, have less inherent DOF. This means that the part of the image which is in sharp focus from front to back is much more narrow. Where that "in-focus" part of the image is depends on where in the image, the lens is actually focused.

Shorter lenses (especially wide-angle) have much more depth of field. The practical impact of this is that with a longer lens, you can get areas -- intentional or not that are out of focus. When you are trying to isolate a subject from its background (or sometimes foreground), this out of focus effect can be pleasing, particularly with a "busy" background. But if you aren't careful, you can also get parts of the image that should be in focus out of focus.

Likewise, a smaller aperture yields greater DOF than a wider one.

I am not certain how much control you have with that on the P&S camera --- but generally not nearly as much.

The "settings" on the camera are usually simply the manufacturer's combination of the above. But then you have the camera doing the "thinking" rather than yourself. Though they are pretty "smart" they are not near as good, in my view, as you are at choosing which of these elements work best in an image.

If you are going to shoot a small aperture with a longish lens in good light conditions for this stuff, you are undoubtedly going to deal with slow shutter speeds. This is why it is critical to have a tripod (and I believe, remote release).

Some will suggest that the self-timer on the camera is just as good -- but there are some problems with it.

You will also have to work with wind and possibly, (on cloudy days) moving light conditions. Its hard to time a let up in wind with the self-timer. If light conditions are rapidly changing, its hard to time them, too.

For a much better organized and readable explanation of DSLR DOF, aperture and shutter speed relationships, you can read the tutorial on my LIGHTCENTRIC PHOTOGRAPHY BLOG, or purchase Bryan Peterson's "Understanding Exposure" (also on my Blog Bookstore). The latter is well worth the few $ and the read. My tutorial? Well, you be the judge :)
Andy

If it sounds too good to be true, its probably . . . .


pwt54
Moderator
Posts: 2728
Joined: Sat Jun 01, 2002 12:01 am
Location: johnson,vermont,usa

Postby pwt54 » Sun Jun 21, 2009 8:27 am

Okay. This does clarify my limited knowledge of dof. The photos of the showy lady slippers were taken with my sx 10 with a range of only f 2.8 to f 8, so I didn't play with the f-stop too much. I used my rebel for most of my spring time wildflower photos and shot each photo with multiple setting. I'll have to study these photos. I don't have time right now. Yesterday my brother had the day off so we went to the Wayside Restuarant for their Beans and Franks special and wandered around the back roads of the Groton State Forest. Today we are going to try the Showy Lady Slippers in Woodbury and wander the back roads around there.

dstainer
Posts: 3
Joined: Mon Aug 10, 2009 4:13 pm
Contact:

More on DOF

Postby dstainer » Thu Aug 27, 2009 10:48 am

Hi Andy,

I think this is an excellent tuturial. Thank you for developing it.

From my perspective, DOF has always been about creative intent. What do you hope to achieve? Do you want shallow DOF or deep? This should be based on your shooting goals.

If shooting leaves up close, extracting them from the “often cluttered” background is critical, which requires you to open the aperture up, thereby blurring the background to create that creamy bokeh that we all love (of course, this is also based in part on chosen aperture, subject distance from background, and your distance from subject/focal length). Assuming decent light, these shots can be handheld because the reciprical shutter speed will be relativly fast. If you have VR on your lens, you can handheld at even slower shutter speeds. If the shutter is too slow, you can always boost ISO, or open up the aperture even more. Of course, there are potential trade offs when doing this, such as increased noise or decreased DOF.

If your intent is to maximize front to back sharpness, then closed down is the way to go. For landscape photography, this is usually the primary goal, and in most cases will require a tripod as you suggest. As a general rule of thumb, around f/11 to f/16 is the preffered DOF/aperture setting. Past this, and you will potentially run into diffraction (which is when the light bends around the aperture opening, which can compromise image quality). Different cameras have different diffraction limits.

Given that the ideal landscape composition should include a foreground element to help establish dimension and perspective while leading the eye into the scene, deep DOF is often critical.

Now if shooting an object that is on one plane of focus where DOF is not really an issue (such as a leaf on the ground), then you’ll want the sharpest aperture your lens can provide, which is usually two stops down from your lens’ base aperture. So if your lens is an f/2.8, then f/5.6 would optically be the sharpest aperture.

As you indicated, DOF is not nearly as much of an issue when using wide angle lenses—because even at wide open apertures, you can often achieve decent DOF, whereas zooms will compress the image and shallow DOF is more pronounced at wider apertures.

The last thing I would add is regarding optimal placement of focus. DOF establishes how wide the range of acceptable focus is. In reality, there is only one real plane of focus/sharpness in any given scene. In other parts of the image, you are merely trying to achieve an acceptable degree of sharpness. Landscape photographers often use a method called hyperfocal, which is basically a formula that can help you identify where in the scene to focus in order to achieve the greatest DOF range.

In layman terms and without getting into the technical details of hyperfocal method, you can usually acheieve maximim DOF by focusing 1/3 of the way into the scene (from the viewfinder bottom). In doing so, 1/3 in front of the focus point and 2/3 behind should be acceptablly sharp. If focusing on a tree in the far distance without any foreground object, this is not so critical (and focusing on infinity would be your best bet in this case). But if you want to (for example), photograph a pumpkin in the foreground and colorful grove of trees in the background, or any other situation that requires you to push your DOF, then this method would help.

Hope I did not get too technical? :D

~Dan

Andy
Site Admin
Posts: 1493
Joined: Sun Sep 18, 2005 12:01 am
Location: Saginaw, Michigan
Contact:

Postby Andy » Thu Aug 27, 2009 3:38 pm

Good stuff, Dan and no -- I don't think too technical. It is dissappointing that most modern lenses do not have the "hyperfocal" markings on them. Whether you completely understood the science behind it or not, it was really an easy technique to set the little greek symbol over the numbers and be confident of maximum DOF.

You (and anyone else here who is a glutton for punishment :) ) might be interested in my recent Blog article on "new" techniques for obtaining great front to back sharp focus, using blending techniques. My LightCentric Photography Blog article: http://lightcentricphotography.blogspot.com/search/label/Equipment[/url]
Andy

If it sounds too good to be true, its probably . . . .

dstainer
Posts: 3
Joined: Mon Aug 10, 2009 4:13 pm
Contact:

Nice Blog!

Postby dstainer » Thu Aug 27, 2009 4:43 pm

Great Blog Andy! Filled with excellent information. And some fantastic gallery images as well. Thanks for sharing. :)

Yes, I agree that newer lenses should include hyperfocal markings.

Personally, I have never bothered too much trying to get exact hyperfocal DOF (using charts, formulas, etc.) and just focus 1/3 into the scene for great results. When I get too wrapped up on the technical, I lose sight of the scene and composition. I'm sure you can relate.

If the scene is really noteworthy, I may focus bracket a little (or even aperture bracket). That's the beauty of digital, you can experiment to your heart's content. And of course stacking is an interesting approach too. I'll have to check that out.

~Dan

pwt54
Moderator
Posts: 2728
Joined: Sat Jun 01, 2002 12:01 am
Location: johnson,vermont,usa

Postby pwt54 » Fri Aug 28, 2009 10:01 am

Boy, am I glad I waited until my 3rd cup of coffee before I checked in. :shock: The photos I took that started this discussion were close ups of flowers. My preference for this is a blurry background. After Andy's post I did try other f-stop settings. I've had fun taking all sorts of photos at different settings, but I'm giving my hard drive a nervous breakdown so I've had to add an external hard drive. I guess the next thing to get is better software, like photoshop, but first I need a new laptop, because this old bugger can not handle photoshop or even elements.

Andy
Site Admin
Posts: 1493
Joined: Sun Sep 18, 2005 12:01 am
Location: Saginaw, Michigan
Contact:

Postby Andy » Fri Aug 28, 2009 3:48 pm

Dan: I can definitely relate. I rely on medium to small apertures and focus 1/3 in most often too. One of the things that got me thinking about using the focus stacking was a general dissatisfaction with some of my front to back scenics. Even with a very sharp w/a lens, I was finding that I wasn't satisfied either with the sharpness of the foreground or the background.

I will be in Acadia NP in October and will definitely be taking some photos purposely designed to "stack."

Phil: One of the things that has been a universal question for serious digital photographers is file management. In the old days, I kept my 35mm slides in notebook pages and would be able to thumb through them. I had a database system of sorts to find things. All I worried about was a cool, dry, dark place to store them. They have held up rather well over the years.

Digital files are so ephemeral. I currently store my images on two different hard drives -- on at home and one at the office. Each is identical and contains identical copies of the images. I used to also burn DVD's but have given that up concluding that they will deteriorate. Fingers crossed that one or the other of my HD's will not fail! Sooner or later, solid state drives will be available at reasonable cost that are large enough.

My advice, though, is to back them up -- preferably in two places!
Andy

If it sounds too good to be true, its probably . . . .



Return to “Vermont Photography Forum”

Who is online

Users browsing this forum: Bing [Bot] and 1 guest