Depth of Field... Again

About the time I think I've got a good understanding of "Depth of FIeld" (DOF) I run into a great article that gives me a new look at this old subject.

Each time I've thought about writing a small piece about it and adding some neat diagrams I think why? There are dozens of examples out there that do that for me.

If you are just trying to grasp the concept of DOF please click on the diagram above to see it larger.  DOF is that area of a photograph that is in focus.  Using DOF and knowing how to manipulate it can greatly improve certain photographs or destroy them if you don't understand it.

I'd suggest that you first focus on Aperture and how it effects DOF and after you master that.  Move on to the other ways you can effect it.

For example did you know that if you double your Aperature from F4 to F8 you will double your DOF.  Or double the distance between your camera and the subject and you will reduce the DOF by 4 times. The same type of thing happens when you increase the focal length of the lens you are using.  Double the focal length and you'll decrease the DOF by 4 times.

I could go on and on but I think you'd do better by reading the two separate blog entries.  The first is where I started at Steve Berardi's PhotoNaturalist blog and "Three things that effect DOF" then from there off to Brian Auer's great blog entry at "Epic Edits" called "Three Ways to Control Depth of Field".   There are several other "gold nuggets" in Steve's entry and Brian has  illistrated this work wonderfully too.

Update on Wednesday, April 14, 2010 at 10:24AM by Tom S.

I made this shot yesterday morning and it is an example of a shallow DOF.  The focus point was the reproductive parts of the flower.  The pedal tips toward the lens are out of focus as is the base of the flower cup.   See if you can locate all the parts of the flower that are on the same plane with the focal point?

The lens was stretched out as far as it would go (108mm full frame) and the FStop selected was 3.5, both contributed to a shallow DOF.  If I had pulled the lens in to 28mm and selected a higher FStop... say F11 or better much of the flower would have been in focus.

DOFMaster

In preparing for tonight I found this wonderful tool that I thought I'd share with you.   It is called DOF Master and amongst many things that I've not completely explored, they have a "Depth of Field" (DOF) calculator.

What is so cool about this is it allows you to adjust your Distance to the subject, the Focal Length of the lens, the F-Stop and the distance to the subject.... all of which effect the DOF.  It then calculates the actual  DOF based on your camera and model..... 

I don't know how accurate it is but as a tool to get your head around the concept of DOF this can't be beat! Well maybe, but this sure is nice.

Head to the DOFMaster website.

Shallow DOF on a Bright Day

ISO 100, F/11, 1/125, Polarized Filter, IS for vertical movement only

This came about after reading Paul P.'s comment in the previous blog entry and I suppose is really dependent on your camera... it's range of ISO and available Shutter Speeds.

He mentioned that "Nancy brought up how hard it is to use the aperture that we like for Depth of Field (DOF) and still work with the available light (lots of it that day) guess a neutral density filter may have helped me with that."

Remember you have three settings that are used to get the correct exposure. Aperture, Shutter Speed and ISO (sensor sensitivity).

I'm not sure if they were in Aperture or Shutter Priority modes so I'll assume Aperture Priority first with the lowest ISO selected. This would allow them to control the exact DOF that they wanted.  Classical Skiing is much slower then other forms so they might have been able to get away with this setup for most of the shot.

In Aperture Priority Mode you select the Aperture and let the camera pick the speed in order to get the correct exposure.  When you lower the Aperture (open the lens) the camera would have to compensate by increasing the shutter speed.  If it had been so bright that by the time they got to F2.8 (the lens was wide open)  and the camera could go no higher in speed then Paul would have been right... They would have had to physically reduce the light getting to the sensor with a filter of some sort.... .

An alternative to a neutral density filter might have been a polarizing filter which might have gotten them one stop closer to what they wanted.  This would have given them the advantages of a brilliantly crisp blue sky if they shot perpendicular to the sun's direct light. In other words the sun was to the left or to the right of the subject. And if they were shooting with the sun to their backs it still would have reduced the over all light levels. (see the photo in this entry. the sun was to the right of the skier).

A bright day can also be a problem source while shooting in Shutter Priority which I most often use while tring to photograph faster moving objects. In this mode I select the shutter speed I want and let the camera select the aperture. Maybe this was the problem, the camera was selecting apertures that were to small (making for a wide DOF).  

Here is something else to think about and where manually adjusting the ISO can help. I've seldom been about to use the faster shutter speeds that my camera offers  while in Shutter Priority Mode.  I usually want higher shutter speeds while shooting sports to freeze a shot.   Using higher ISO (making the sensor very sensitive) allows me to select much higher shutter speeds to reduce the light getting to the sensor.

On a bright day with out much shadow you will not get as much grain at the higher ISO so experiment some and see how your camera works.  If you have one of the top of the line Nikons or Sony.. don't worry about it. They can shot some incredible high ISO settings with little or no grain.  The rest of us will just have to dream! Ha....

What do you think? W hat am I missing here?

Introduction to "Depth of Field"

F8.0 - Focal Length 105mm - Photographer Bruce S.I'm sure that the audience that visits here has a wide understanding of the terminology used in photography, so this introduction to the concept of "Depth of Field" (DOF) will only present the basics and give you a link to more information.

For the sake of this introduction we will assume that there is only one point, one distance from the camera in any photograph that is in absolute focus. (The exception to this might be where the subject is so far away that it and everything to infinity is in focus.) When your subject is close, there is a zone of focus where everything a short distance before and after the subject appears to be in focus. This zone is call the "Depth of Field" (DOF). The word APPEARS needs to be stressed for what really happens is that the amount of focus degrades from the central true focus point as you move closer to the camera or further away from the subject. 

Click to read more ...