If you were to talk to many of my workshop attendees and they will tell you there are a few things I really espouse throughout the workshop, hopefully not to the point that its information overload. One of these techniques is DEPTH of FIELD. Some of of my attendees did not know what depth of field is, let alone how to achieve it. Some didn’t understand it and others thought it too complicated and therefore have never mastered the techniques. Well, it’s not complicated at all, once you understand it, and perhaps this essay will help explain it to you in as easy terms possible. I will state that Depth of Field is essential in every form of photography and must be understood and applied.
So, what exactly is depth of field? Simply, it is the amount of detail, within the image that is in focus. You, the photographer must decide on how much depth of field (DOF) is desired. Do you want the entire image in focus? Do you want the background out of focus ( often referred to as blown out—-I don’t really like that term as “blown out” might refer to overexposed, not out of focus).
Once you make the decision on how much of the image you want in focus, you must understand the technique that must be used to achieve your goals.
Decisions on setting to attain Depth of field are:
The F-Stop (see below) chosen to make the image
The focal length of the lens
Subject size (the depth of field decreases as you decrease the lens/subject distance
How far away is the subject?
LENS OPTIONS
Choosing a lens will have a dramatic effect on your depth of field. Lenses below the 60mm range are capable of attaining a large depth of field. (wide angle lenses) The DOF affect attained with lenses above 60mm will be less and when combining a 160mm+ lens on a DSLR, perfect Depth of field is virtually impossible. This is a principle of physics.
This old barn was photographed at F16 using a 80-200mm lens at 140mm. Notice the inability to make the background perfectly sharp
After reading this article, when in the field, try attaining a sharp image front to back with a 200mm lens on a DSLR. You will quickly see that it is impossible, due to the way the plane of the lens lies on the camera. It’s nothing you did wrong as long as the majority of the image is in focus. I’ll discuss options to attain DOF when using long lenses later.
CHOOSING APERTURE
I’ll try making this as simple as possible, but you need to understand exactly what aperture is, in order to be successful attaining proper Depth of field.
The aperture setting refers to the hole that the light passes through when the shutter opens, similar to the iris in our eyes. You can change this setting in camera. These settings are referred to as F stops. F-stop is the focal length divided by the diameter of the lens. F stops are typically written as F/4 etc.. meaning focal-length over 4 or focal-length divided by four.
Each F stop one lets in 1/2 as much light as the previous one. The progression of F-stops, 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 – 32, are powers of the square root of 2.
In the field, you decide on how you want your image to appear. Do you want the image to be sharp front to back or do you want a sharp subject and less sharp background. If you make the decision to make the background less sharp, to accentuate the subject, what level of “unsharpened” do you want the background to be? (This is why we need to think when we photograph… slow down and calculate what you are trying to attain in each image).
Think about this…Not all great landscape images are shot at F22 !
Aperture setting dictates what shutter speed you have. F8 at a 125th sec is exactly the same exposure as… F at 11/ 60th … or … F5.6 at 250th sec… however the aperture (F stop settings) determine the depth of field.
Yaquina Head Lighthouse, Oregon Coast aperture=F16
Same as on Left aperture= F 5.6
F 16
F 5.6
Which do you like?.. It’s really up to you!
Considerations:
1) On a windy day, shooting at F16 or F22 can you attain a shutter speed high enough to freeze the blowing grasses?
2) If a scene is too dark and you need a large Depth of field (F22) meter open enough to focus, then adjust the shutter speed for the aperture you want.
The rule of thumb is, the larger the F stop (F16), the smaller the aperture, and the more Depth of field you have. Conversely, the smaller the F stop (F4), the larger the aperture, and the less depth of field. Yes, there are counterintuitive to our thinking but you’ll get used to how these setting work pretty quickly.
SETTING THE DEPTH OF FIELD
USE YOUR DOF BUTTON !!
I strongly recommend that nature photographers use only two modes to make photographs on their camera. These are the manual mode or aperture priority mode
I strongly recommend that if you do not have a camera with a depth of field preview button, look to upgrade to one that does. This button is invaluable… What it does is that it stops the lens down to the shooting aperture and shows you, through the viewfinder how the depth of field will appear in the photograph. Without this button , when looking through your lens you’re looking at the widest aperture the lens will provide, not the depth of field that the aperture setting you’ve chosen will represent.
Note:—if your camera is set in the AUTO FOCUS mode——your camera will negate all your hard work setting the DOF manually. A while ago, I was conducting a workshop and a participant asked why when he focus correctly, and uses his Depthof Field Button (DOF) to check his DOF and his images still turn out blurry. Well he had his camera set to auto focus, and when he pressed down on the shutter release the lens went into auto focus mode, thus canceling out all the work he did manually to create the image he wanted.
Here is an easy technique to make images sharp from front to back, (remember this is a discussion when using lenses under 60mm!)
“OK, AT F16 my viewfinder is so dark when the DOF button is pressed that I can’ t see the image, let alone the adjust of the depth of field”
At small apertures like F11, F16 the viewfinder does becomes too dark while depressing the DOF preview button.
Here how to make it work!
Set your aperture to F8 or to a setting you can see the image through the viewfinder while depressing the DOF Preview button.
Focus just above the 1/3 of the way up from the bottom of the frame on a subject closest to you, and then fine tune the focus, looking into the image itself, checking the background for depth of field.
If this area is in focus, you have a great chance of the entire image being in focus when resetting the aperture to F16, or even F22
Having done that accurately, I the reset my aperture to F16 or higher and make the photograph
Some cameras have a zoom capability in playback. Zoom in, using the LCD on the back of the camera on the background to check for sharpness.
To make a photograph using a subject that is sharp with an unsharp background you must
300mm lens at F8
1) Use your depth of field preview button to focus on the subject
2) Set your aperture where you want it to attain the desired background, probably less than n F8
To me this technique is a bit easier than having the entire image in sharp focus. I love photographing wildflowers with a long lens (300mm) to really make the flower the subject stand out, and make the background unfocused.( the longer the focal length lens, the more you can really make the background blurred out.).
OTHER HELP FULL HINTS to ATTAIN PROPER DOF
this image was made up of 7 images combined using Helicon Focus
1) There is a program available called Helicon Focus. Helicon Focus is a program that creates one completely focused image from several partially focused images by combining the images (you can use an unlimited amount of images) into one focused image. The program is designed for macro photography, micro photography and hyper focal landscape photography to cope with the shallow depth-of-field problem. Helicon Focus also aligns images as objects often change their size and position from shot to shot. This function is especially important for macro photography but works quite well in certain conditions in landscape photography as well. I am very impressed on how easy the software is to use. The software can be downloaded right off the web site www.heliconsoft.com.
It’s been my experience that you really need to know in advance, in the field if you will be shooting using the HF program. Not all images will lend themselves for Helicon Focus. Any movement at all will ruin the otherwise great results. This is a good tool to use when using longer focal length lenses, however all lenses qualify if the criteria of: 1) light not changing and 2) the subject matter is not moving is met.
2) Not too long ago, lens manufacturers used to include depth of field guide marks on their lenses… but not any more. If you would like a handy little replacement for these marks, something that will let you can download Depth of Field calculators and determine the settings and effects of different focal lengths and aperture settings via the web and smart phone’s. I do not use these.(I’ll explain later)
3) I’ve seen folks with a depth of field calculator. I don‘t know who makes it but it’s a wheel that after you put in your aperture & shutter speeds, it will tell you how many feet out you need to focus. Again unnecessary.
Why do I think # 2 & 3 are unnecessary? Probably sometimes when the light is constant and you do have the time to figure these applications out they might be useful. Consider these 2 factors; 1) are you capable of gauging exactly how far, say 23 feet is from your camera? I don’t think I can. I may be at 24 or 22 feet or even further away from the target. 2) More importantly, during sunrise, sunset, the light is changing, you don’t have time to be there holding your smart phone, changing the aperture with the light, seeing out a reading that you probably can’t be accurate on anyway. You’ll miss the shot, or get it wrong. Try the method of focusing 1/3rd up from the bottom, it will work very accurately, once you get used to it.
4) Look into shooting large format cameras. These cameras, because of how their lenses work in relationship to the camera, and some other factors, will attain a large amount of depth of field using longer focal lengths.
Understanding and using these techniques are primary in your ability to make images the way you desire. Like anything else it takes practice and understanding of the concepts.
F22
F 5.6
Read more about Jack on his website here, and learn about his workshops here.
I am amazed that there is a debate still going on about why anyone would want to use a DSLR for shooting serious video. The arguments remind me of the early days of digital photography, where many out there would argue that images NOT taken on film were not real photos. Today we know differently.
To this end I want to share with you why I shoot video with a DSLR, what I find the be the advantages and disadvantages of using what many are now referring to HDDSLRs (I personally prefer the term Video DSLR).
In this first installment I will talk about what is great about shooting video with DSLRs. Tomorrow I will follow-up with what I consider to be the shortcomings of such systems.
Multiple lenses
This is by far the most important reason for me to use a DSLR to shoot videos. I can use my entire arsenal of still lenses. I can use my macro lenses, my wide angle 10mm, my Super-telephoto 500mm, even tilt-shift lenses. This flexibility is completely unprecedented, that is, unless you had a large personal fortune you did not mind spending it on lenses and cameras. I grew increasingly frustrated with my previous video camera because I could not capture the macro images I wanted to film due to the lens limitations of my camera. The Yellowstone video above I would not have been to capture if I had not been able to shoot with my 500mm lens. Yes there are video camera systems with even greater reach and incredible zooms, but some of these can cost more than $100,000, and at those prices these are out of reach for most people; including myself.
Low Light Capabilities
Because of the large sensors DSLRs have, these cameras have what could be considered nothing short of spectacular low light capabilities. Art Howard, on a recent assignment, was able to shoot video of sleeping bats inside a cave using nothing more than the headlamps they were wearing. Last year I was able to capture some great footage of Pine Barrens Tree Frogs using nothing more than a small battery powered lamp, as you can see the in the video below. Neither of these shoots would be been possible under the circumstances with traditional video equipment as these shoots would have required significant lights, which would have been impossible to use in either of these two situations.
In photography we control the depth of field in our images by adjusting the aperture on our cameras. The wider the aperture, the shallower the depth of field. But did you know that your cameras sensor size also affects the depth of field? True! All other things being equal such as lens and aperture, two cameras with different sensor sizes will produce different depths-of-field. For example, a Canon 5D MarkII will produce a shallower depth of field than a Canon 7D, as the 5DII has a larger sensor than the 7D.
You may now be asking, why does that matter? It matters a lot, as most video cameras have TINY sensors, typically 1/3″ or 1/4″ or 1/5″, compared to a full frame still camera sensor, which is about 1.4″. What this means is that video cameras have a very deep depth of field. Think about this for a minute. As a still photographer, if I took away from you the following apertures (2.8, 5.6, 8) how would you feel? I know I would feel severely limited creatively. That's how I felt when using a video camera. True, I’ll take as much DOF as I can get when shooting macro, but everywhere else, I rather have my entire DOF range at my disposal, to use as I please.
This DOF issue is one of the primary reasons why most movies are still shot using film. Film is a LOT more expensive to shoot with, you can’t see the results immediately, and it’s a hassle to deal with. Independent filmmakers have been embracing the DSLR for movie making in droves, because the DOF control these systems offer allows them the tell their stories better without the expense of using film.
This is my last point, but by no means the least important. ONE SYSTEM. What I mean by this is that I have one type of battery, one type of charger, one type of memory cards, one type of lenses, one type of tripods and camera plates, etc. I don’t have to carry multiple formats of the same thing as my photo equipment serves multiple purposes. But MOST important, I only need to learn and know how to operate ONE type of camera. No need to learn multiple switches, dials, controls, menus, capabilities, limitations, etc. These are the same properties of my still camera, because IT IS my still camera. I know the controls of my camera to the point I don’t need to think about them or look at the camera to make any changes, I just “know” how to make these changes without even thinking about it. This is hugely important, because when you need to make a quick adjustment, you just make it, no thinking about it, no need to try and remember where the controls are on this camera, it just happens, and consequently I get the shots I am looking for, more often than not.
The video landscape is not all rosy--there are certain limitations and issues. I'll cover those issues tomorrow, and what I do to overcome them.
However, in my opinion, the positives FAR outweigh the negatives, but you need to decide that for yourself. Hopefully these articles will help you make your own decision.
This Podcast was originally released as a Martin Bailey Photography Podcast on Apr 12, 2008.
Prefer to listen? There’s an audio player at the bottom of the post.
I’ve rarely seen an easy to understand explanation of how the aperture and distance to the subject affects the depth-of-field in our images. When I started to think about how I would explain this, I started to understand why, because it wasn’t easy to do this in a simply way, and I still am not sure if I’ve succeeded. I’m sure you’ll let me know. Anyway, I’ve created six diagrams to help me explain this. I’ve not attempted to draw scientifically accurate diagrams, rather just created them in Microsoft Word to help me explain more easily with words. So let’s jump right into it and attack what should be a very simple subject, though it never seems to be.
I’ve included the diagrams below, but I also published a rough PDF of the diagrams, as it might be easier to compare the diagrams by just flicking through the pages of the PDF. If you move page by page rather than scrolling, you see the next chart an instant after the first, so it’s very easy to see the changes.
Anyway, let’s go ahead and look at Diagram #1. You can see that I’ve basically drawn a mock-up of a lens, with a few lens elements, and an aperture ring. The dotted line running through the center of the lens is the lens axis, and the thin blue lines that make their way through the lens from the film plane to the point we are focusing on in basically representing the light coming into the camera. I’ve used the actual metrics associated with a 50mm lens, and for now, we are focusing at 2m, or around 6.6ft, and I’ve made the aperture F2.8, which I’m imagining is pretty much wide open for this 50mm lens.
Diagram #1
What I want you to take note of right now is the X that the blue lines makes as it intersects at the point at which we have focused the lens, two meters in front of the lens. Either side of the X I have drawn a circle. You can think of this circle as the circle of confusion if that helps. If you don’t understand what the circle of confusion is, take a listen to Episode #65 when I discussed Hyper-focal Distance. It’s not important that you fully understand what the circle of confusion is right now though. Just think of it like this. As we move away from the point that we are focused on, the elements in the frame start to become less sharp. The point that we are focused on is the most sharp, but even before we leave what we call the depth-of-field, things start to get closer to being what we’d consider out of focus. These circles represent the nearest and furthest points at which the subject or elements around it will still be perceived by us as being in focus. In the diagrams I’ve called this the far limit and the near limit of acceptable sharpness. So, the light travels from the scene, into the camera through the lens, and the elements within the lens move around when we focus to make sure that the image comes into focus at the focal point on the film or sensor that we can see as a dotted line on the bottom right of the diagram. Although some of the lens elements do move around in reality, it’s not important to understand this concept, so I’ve not changed them in the diagrams.
Before we move on to the next diagram, let’s note the size of the depth-of-field when focusing at 2m with a 50mm lens. The depth of field is 27cm, or just over 10 inches. Also visually note the angle of the intersecting lines that make the X at the point at which we are focusing. Let’s now take a look at Diagram #2.
Diagram #2
The only difference between diagram one and two, is I’ve stopped the aperture down by two stops from F2.8 to F5.6. You’ll see that the angle of the intersecting lines making the X at the point we are focusing on, still 2 meters, is now much closer. So that we are all thinking the same way, imagine you are looking at the X from the front of the lens, so the lines just got closer. Now, the circles that represent the near and far limits of acceptable sharpness have to be moved further out so that they fit between the lines. With just two stops smaller aperture, the depth-of-field widens from 27cms, to 54cms, almost double. This is because we are focusing at 2m, just over six feet from the film plane.
Let’s look at one more diagram while focusing at 2m. In Diagram #3 we will close the aperture by a further two stops to F11. Look how close the two intersecting lines of the X at the point we are focused on are now. We can also see that the depth-of-field has increased greatly. Now to get the two circles of acceptable sharpness between the lines, we have to move them much further apart. The depth-of-field increases to 1.14m, or 3.74ft. Compared to the 27cm we had with an aperture of F2.8 focused at 2m, we now have over four times more depth of field. So, we have seen here that even at the same distance to subject, we can greatly increase our depth-of-field, just by making the aperture smaller.
Diagram #3
In addition to the aperture though, distance to subject, even at the same aperture has a huge effect on the depth-of-field. Obviously, because the lines of the X that we’ve been looking at continue to move apart, and the further away from the depth-of-field, or the area of acceptable sharpness they get, the more blurred the foreground and background gets. This is why the more acute the angle of the X the more quickly we start to see lots of out of focus areas, or bokeh. In Diagram #4 I’ve scaled the diagram down to around 1/2 size so that we can get it on the page, but if you look at the numbers and the size of the camera etc. I don’t think this will be too confusing.
Diagram #4
Anyway, what we’ve done now is kept the aperture at F5.6, which is of course relatively wide, but now we’ve focused on something 5m or 16.4ft away. Look how much closer the lines of the intersecting X are now compared to diagram #2 when we were focusing at just 2m. The depth-of-field has also increased from 54cm or 1.7ft to a whopping 3.8m or 12.5ft. This is seven times more depth-of-field, just by focusing at 5m instead of 2m. So now we can see how focusing further away increases the depth-of-field even with the same aperture.
Just to reinforce this, let’s now look at Diagram #5, and focus much closer to the lens. Let’s imagine we focus at 50cm, or 1.65ft in front of the film plane. All focusing distances are measured from the film plane by the way, so it’s not a problem thinking about the distance from the film plane instead of from the front element of your lens. Still with an aperture of F5.6, see how wide the lines of the intersecting X are now, and how close the circles of near and far acceptable sharpness now are. We have a depth-of-field of just 3cm, or just over an inch.
Diagram #5
If we open the aperture up to F2.8, as in Diagram #6, we can see that the lines of the X get even wider apart, and the depth-of-field is reduced to 2cm, or just over half an inch. If we compare this to Diagram #1, when we focused at 2m with the same F2.8, the depth-of-field has reduced from 27cm to just 2cm, by changing the focusing distance from 2m to 50cm, or one quarter of the distance.
Diagram #6
I think we’ve probably had enough of diagrams now, so I didn’t make any more, but I’m sure this will help you to appreciate why the depth-of-field gets so much shallower when doing very close macro work. Sometimes we’re focusing on things just in front of the lens, literally, if working at magnifications larger than life size. Say I’m using a short macro lens, and focusing on something very close to the lens, at about 20cm from the film plane, my depth-of-field is reduced to 2mm, because the lines of the X intersect at such a wide angle. When you do go larger than life size, it is not uncommon to have a depth-of-field of less than a millimeter, and have to stop down to F11 or F16 to get more than a millimeter.
The other thing to bear in mind is that focal length has an influence of depth-of-field as well. The reason for this is because if we still focus at 2m, say with a 100mm lens, instead of a 50mm lens, the subject is magnified to twice the size. This in turn means that we are magnifying the circles of acceptable sharpness, so they go out of focus twice as much. To counter this we have to half the size of the circle for it to still be acceptably sharp, and that means that the circles move closer to the intersection of the X, and the depth-of-field decreases. Basically the longer the focal length of our length, the smaller the circles of acceptable sharpness get.
Anyway, I hope this has helped if you didn’t really understand why aperture and subject distance affected the depth-of-field the way it does. If you are still confused, how about grabbing a small object, and a tape measure, and setting up your camera on a tripod and put the object 2m away from the camera, and take three photos. One with your lens wide open, then stop down by 2 stops, so if you start at F2.8 you’ll go to F5.6 and a third having stopped down by 2 more stops, so F11. If your lenses widest aperture is F4, try F4, F8 and F16. Then move the object you shot to 50cm, or as close as you can focus on it, if your lens doesn’t focus as close as this, and shoot three more shots with the same three apertures. Then move the object out to 5m, and repeat the three shots. Then take a look at your images on your computer, and you will be able to see the difference very clearly.
Another very simple trick you can try is to hold out your finger, at arm’s length, and focus on it. Notice how blurred the background is using your peripheral vision, that is don’t actually focus on the background, just see it while focusing on your finger. Then move your finger towards your eyes, while continuing to focus on it, kind of like in AI Servo or continuous focusing mode. As your finger gets closer, you’ll notice that your surrounding go out of focus even more. Move the finger back out, and the surrounds become more focused. You can do this with both eyes open or just one and see the effect, but bear in mind that your camera only has one lens, so closing one eye should help you to see very much as your eye does.
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If you were to talk to many of my workshop attendees and they will tell you there are a few things I really espouse throughout the workshop, hopefully not to the point that its information overload. One of these techniques is DEPTH of FIELD. Some of of my attendees did not know what depth of field is, let alone how to achieve it. Some didn’t understand it and others thought it too complicated and therefore have never mastered the techniques. Well, it’s not complicated at all, once you understand it, and perhaps this essay will help explain it to you in as easy terms possible. I will state that Depth of Field is essential in every form of photography and must be understood and applied.
Each F stop one lets in 1/2 as much light as the previous one. The progression of F-stops, 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 – 32, are powers of the square root of 2.
F 16
At small apertures like F11, F16 the viewfinder does becomes too dark while depressing the DOF preview button.
2) Not too long ago, lens manufacturers used to include depth of field guide marks on their lenses… but not any more. If you would like a handy little replacement for these marks, something that will let you can download Depth of Field calculators and determine the settings and effects of different focal lengths and aperture settings via the web and smart phone’s. I do not use these.(I’ll explain later)
Before we move on to the next diagram, let’s note the size of the depth-of-field when focusing at 2m with a 50mm lens. The depth of field is 27cm, or just over 10 inches. Also visually note the angle of the intersecting lines that make the X at the point at which we are focusing. Let’s now take a look at Diagram #2.
