A deeper look into Depth of Field

A deeper look into Depth of Field

A Guest post by Reader Josh Wells

A shallow depth of field is highly sought after due to it’s ability to separate the subject from it’s background and is found in many professional photographs. By now your probably know that larger apertures (f/2.8 and below) correlate to a shallower depth of field whereas small apertures (f/16 and above) will render almost the entire frame in focus. In this tutorial I will explain further factors into controlling depth of field, how much is too much and why different sensor and film sizes give different depths of field.

F/ Stops

F/ Stops are generally the hardest of the three elements contributing to exposure to grasp. Both because of their inverse relationship with brightness and because it’s often hard to understand what is actually happening when you change apertures. To understand this fully it is important to understand what an F/ Stop really means. An F/ Stop meaning Focal stop, is the fraction of a lens’s focal length as measured (Widthwise) passing through the lens, in order to keep the same amount of light. Still confused? Here are some diagrams of how an aperture of F/2 is measured for a 50mm lens and a 100mm lens.


Whilst scoring no points for artistic merit, I hope these help explain how F/ Stops are measured and how each of these lenses will give the same exposure at each aperture setting. More advanced lenses such as those used in cinematography use T/ Stops or Transmission stops, which factor in the amount of light a lens loses through the elements to give the true amount of light input from the lens. However since this tutorial is about depth of field we do not need to worry about T/ Stops so much.

This aperture as it gets wider effectively baffles the light, so eventually it can only be focused to one small point, bringing the rest out of focus. As it becomes smaller (For example a 20mm lens will have only a 10mm aperture at f/2, meaning a deep depth of field) the light will be less baffled and the lens will have better control focusing it in and around the required focal point.

So how do we get depth of field?

Depth of field is ultimately effected by two things: The aperture of the lens as we have just covered and the distance between subject and background. If you have a lens with the focus distances marked on it have a look at it now, you’ll notice that the distance the focus ring needs to be pushed to go from 7 to 15 feet (Or at 2 to 5 metres for us using the metric system) is about the same as from 2.5 to 3 feet (Or at 0.8 to 1 metres). And then there is hardly any distance from 25 feet to infinity (Try with 15 metres too). So at f/4 on a 50mm lens I could have from 25 feet and everything behind that in focus, or I could have almost the distance between 6 and 4.5 feet.

To utilize this for the shallowest possible depth of field, try to bring as much separation as possible between the subject in focus and the background, for example a headshot will render a distant background out of focus at almost any aperture. If the lens you grabbed also has marks for the depth of field at each given aperture you’ll be able to see how this distance effects each F/ Stop.

Crop Sensors

This can get a bit confusing when you account for different sensor sizes such as APS-C as used by many consumer DSLRs, Four Thirds, and Medium format from some film cameras and some very expensive digital ones. Many people make the correlation between focal length and depth of field and assume that a cropped or four thirds sensor will equal a longer focal length and therefore shallower depth of field. This is not the case due to a cropped sensor working more as the name entails, and literally shooting from an equivalent crop of what would appear on a full frame sensor. Lets explain this with math.

We’ll use a 50mm f/1.8 lens.

So this lens currently has a maximum aperture of 50/1.8 – 50mm/1.8= 27.7mm Aperture

Now lets put this on an APS-C cropped sensor with a crop of 1.6x – 50mm*1.6= 80mm Equivalent Focal length

However the maximum aperture is still 27.7mm. – 80mm Equivalent focal Length / 27.7 Aperture = ~2.8 New equivalent aperture.

We can now think of the lens rather than as an 80mm F/1.8 but more accurately as an 80mm F/2.8.

This also works the other way with larger sensors, which have reversed crop factors and can thus have for example a 90mm F/2.8 lens which will give a crop factor around 0.6.

90*0.6= 54.

Meaning with a medium format sensor of film one can have the depth of field of a 90mm F/2.8 lens however with the angle of view of a near 50mm lens.

Too much Bokeh?!

Whilst in many cases when we want to throw a background out of focus we want as shallow a depth of field as we can afford, there are several cases in which one must find ways to deepen depth of field.

One of the reasons one may have too shallow a depth of field is in Wildlife photography where focal lengths in excess of 300mm are required in order not to disturb the animals, especially when shooting birds. Avian photography can sometimes have so shallow a depth of field that it becomes impossible to accurately focus, or difficult to keep the entire bird in focus due to excessive depth of field. This is avoided through stopping down to smaller apertures and sometimes a flash extender is required to sufficiently light the subject. Such as this Visual Echoes FX3 Better Beamer Flash Extender for Use FX3 B&H or more simple DIY ones.

Another is in Macro photography in which our other variable; Distance, is pushed to an extreme. In macro photography it is not uncommon to require stopping down to f/ 32 in order to gain the necessary depth of field. The light loss from this is aided again with flashes specifically for Macro, often ring flashes.

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Some Older Comments

  • Paul March 6, 2012 11:27 pm

    Thanks, interesting, don't under estimate distance from subject also has a big impact.

  • Jeff Cofer December 3, 2011 04:33 am

    I shoot with a crop sensor SLR and a point and shoot super zoom. On the super zoom, I can lock the exposure and then adjust the aperture to stop down if I want greater depth of field. then I can half press the shutter to lock the focus. I agree that the 1/3 before the focal point and 2/3 behind rule of thumb will impact whether I focus on a near element in my scene or a further away element. To get greater separation from subject to background, I will keep subject close, focus on subject or a little closer, keep the background distant, and shoot aperture priority set to wide open. (Actually can shoot in program mode, as camera picks wide open aperture by default).

    On the SLR, my wide apertures are larger so it is hard for me to compare results to the point and shoots. You get what you pay for. Any one have a full frame and crop sensor body that can confirm that the equivalent aperture is smaller? I would like to think that my 105MM F2.8 is equivalent to a 150 MM F2.8, but I suspect that I am not that lucky.

  • John Madden November 9, 2011 02:38 pm


    I agree completely.

    It is interesting to watch as technology gets better and better it makes it harder to differentiate the advantages of one size sensor over the other. Full size has the advantage in low light and probably image quality for equivalent MP but, for size and price, crop sensors are pretty darn close these days.

  • Marco November 7, 2011 10:02 am

    @john madden While what you say is true to an extent, the full size sensor would need to have more pixels available. A full size sensor of 21 mp could be cropped to the image size and quality of my 18 mp crop sensor on the 7D. Cropping an 18 mp full frame sensor would lose many pixels and have lower quality for large prints compared to the 7D's 18 mp sensor. One of the big advantages of full frame is that the pixels are on a larger frame and don't overheat as much as the APS-C sensor might. That is definitely an advantage for portrait work or fashion photography where you can position yourself in range of your subject easily. Less heat means less noise. However that advantage is lost if you push the pixels closer together to get more MPs as they are just as close as the smaller sensor with less MPs. All things are a trade off and for wildlife action shots, the crop sensor makes a lot of sense.

  • John Madden November 6, 2011 02:08 pm

    Just to clarify (and I know most of you probably already know this), a crop sensor does not give you more reach. A 200mm lens projects the exact same image to a crop sensor as a full size sensor. It just appears to give more magnification because to fill say an 8x10 print the crop sensor image has to be magnified more than the image from the full size sensor. If you crop the full size sensor image to the same physical size it is the exact same image. My point is (as others are pointing out) is that it doesn't matter what camera you put a lens on the image it produces doesn't change. All sensor size determines is how much of that image is captured.

  • GariRae November 6, 2011 11:50 am

    I think the best operational explanation of DOF lie in the iPhone app DOF master. Plug in the focal length, aperture, and focus distance (camera to subject) and the app gives you your DOF distances. Great app for confirming DOF before you shoot and eventually leads to understanding the impact of changing these variables.

  • Marco November 6, 2011 05:42 am

    This article is confusing Bokah with "out of focus" adding to the confusion. Bokah is a physical property of a lens that has nothing to do with out of focus other than how it renders the out of focus areas. Bokah has everything to do with the number of blades in the shutter and the shape of the blades. The more of them that you have and how smoothly that resemble a circle impacts Bokah, but Bokah should not be in this article.

    I also agree with others that the amount of "out of focus area" is dependent on the lens not the sensor. A crop sensor with give us more "reach" with a given lens, but will not change the "out of focus area" at all. A crop sensor will change the apparent size of an object in the frame, but the background will be the same amount of "out of focus area". In other words, the crop factor has nothing to do with the Aperture setting which is dependent on the physical focal length of the lens.

  • Greg Lawrence November 6, 2011 02:44 am

    I understand that the author's intentions were for the good of all; however, in an effort to provide some rational to the various replies and counter-replies, perhaps we should access reliable internet references on depth-of-field and bokeh:



    More to the point, the discussion is about focus and the apparent sharpness perceived in the captured image, as well as the esthetic appearance of out-of-focus areas of the captured image. Resolution is the greatest at the plane of critical focus (not necessarily flat or equally sharp at the edges) in the image for any given lens. The design and condition of the lens determine the quality of that critical focus assuming no subject or camera movement.

    As the distance increases in front and back from that critical plane of focus in the image, resolution declines. Circle of confusion is a value depending on the lens focal length that defines the point at which the loss of focus resolution is noticeable, which defines depth-of-field, usually stated as 1/3 in front and 2/3 in back of the critical plane of focus. Depth-of-field increases as the aperture diameter becomes smaller. In reality, depth-of-field is the area before and after the plane of critical focus that appears to be in acceptable focus.

    Bokeh is an esthetic definition of the appearance of the out-of-focus areas outside of the defined depth-of-field. Selected aperture, lens/aperture design, lens quality, objects and illumination in the foreground/background and their distance from the critical plane of focus all contribute to how out-of-focus areas appear in the captured image. Bokeh is often thought of as just the aperture shaped highlights in the out-of-focus background, but the term applies to all of the out-of-focus areas of the image.

    Applied as practical photographic technique; as desired, select the lens focal length for the field of view and perspective, place the camera and subject to obtain separation from foreground and background, select the aperture for depth-of-field, and carefully focus on the most important area of the subject. This begs the question, what aperture should be used. Current DSLR lenses seldom have the depth-of-field indicators on the focus ring. The widest aperture view through the viewfinder does not reveal depth-of-field for other apertures. Aperture preview with live view or through the viewfinder, hyperfocal chart for that specific lens, approximation based on experience, or test image viewed on the camera display are the usual methods to verify depth-of-field.

    Want to create and control bokeh, use normal to telephoto focal length lenses, closer camera to subject distances, wider apertures, separate subject from background, and have a source of illumination in the background to obtain the typical background bokeh with aperture shapes. Granted there are exceptions to these general guidelines.

    Hopefully this helps.

  • Eric Magnuson November 5, 2011 02:39 am

    Youssef, although it may not be explained well in this article, bokeh has entirely everything to do with DoF. It is also a physical property of a lens. It is simply the physical rendering shaped by a lens of the parts of an image that are out of focus.

  • Kevin Sanders November 4, 2011 11:13 pm

    Hello Josh,
    I read this article when I set up RSS feeds in my email client.
    Until I started this comment I hadn't seen youssefs comment, but I have to say that I agree with him totally.
    Your article was incomprehensible to me and I like to think of myself as tech savvy. I'm an engineer and a somputer programmer and a keen amateur photographer, but some of oyour statements made no sense at all.
    "An F/stop meaning Focal stop, is the fraction of a lens' focal length as measured (widthwise) passing through the lens, in order to keep the same amount of light" Confused? I'll say. "focal length as measured widthwise"? What does that mean? And why, by example, give two lenses with exactly the same F number? How could we infer anything from that?
    I appreciate your trying to be helpful, but articles like this are likely to put people off photography altogether. I think you should remove it.

  • Youssef Ismail November 4, 2011 01:54 pm

    Are you kidding? This article made no sense what so ever. I have been behind a camera for the last 20 years and I think this is the poorest explanation I have ever read. You further confuse the concept with Bokeh. Why is that even in an article about depth of field? The depth of field or depth of focus is a physical property of a lens and the subject being photographed and how far that subject is from the camera and is related to four parameters: lens focal length, the size of the aperture, the size of the subject and the distance from camera to subject.

  • John Madden November 4, 2011 12:56 pm

    Thanks for the article.
    What seems always to be left out in the discussion over equivalent focal lengths on crop vs. full size sensors is framing. I think this is because we tend to think in terms of telephoto capabilities more than closeup shooting. We all want that lens that can reach out and focus a birds eye at 100 yds but, we tend not to think so much about magnification on closeups. The argument is always a 50 mm f1.8 gives the same DOF on a crop vs. full size sensor when used at the same distance from the subject etc.

    But, no one does this in the real world.

    You don't usually take a picture on a full frame DSLR with the intent to crop it down 1.6 or cut off part of your subject when shooting a crop sensor. You move closer or back up to frame the picture most effectively. This is where the term equivalent focal length has meaning. A 50mm lens acts like a 75 mm lens on a crop sensor from a framing perspective. To frame a shot the same on a crop sensor as it would be framed on a full size sensor (with the same lens) you have to back up and take the picture from further away.

    And DOF will be different using full frame vs crop not because the sensor is different but, to get the appropriate framing and composition where the subject, it's background, and camera are in relation to each other is different .


  • Tom Schriefer November 4, 2011 04:11 am

    You seem to be adding to the DOF confusion. DOF is dependent on MAGNIFICATION and aperture. It is a physical property of light. You can't change it by putting the same lens on a different crop-factor body. A 50mm lens (or any other FL) at f/2.0 (or any other aperture) will give the same DOF on a full-frame or a crop sensor WHEN THE SUBJECT IS THE SAME SIZE IN THE FRAME. Try it. This is a miraculously simple concept if you don't try to clutter it up with irrelevant information. Sensor size has absolutely NOTHING to do with DOF.

  • Josh November 4, 2011 01:33 am

    *on a full frame sensor.

  • Josh November 4, 2011 01:27 am

    Whilst your 50mm will not produce 'more' bokeh on a full frame sensor, it will produce the same amount however equivalent to having been 'zoomed out' further. And thus when the subject takes the same amount of space within the frame, the focusing distance will be closer and thus allow for more bokeh.

    You're right about the cropping, what changes isn't the light rays but the equivalent focal length of the lens, and as I wrote in the article, a longer focal length will generally have a larger physical aperture, and thus more depth of field. And thus for full frame to produce the same field of view to depth of field equivalent, you would have to use an 80mm f/2.7

  • Konstantin November 4, 2011 01:05 am

    Josh, thank you for your answer. Just to clarify, do you mean to say that Minolta 50mm f1.7 lens will produce more bokeh on a full frame sensor than on the APS-C Nex sensor? I am asking because this is what you imply by recalculating the f-number to 2.7 full-frame equivalent.

    However, if I cropped an image shot on a full frame sensor by x1.6 would the amount of bokeh on this image change? Obviously, not - this is just a cropped version of the same image. So, similarly, a smaller sensor is just a cropped version of a bigger full frame sensor. And the nature of light rays hitting the sensor does not change no matter the sensor size. It's only the part of the image you see through the same lens which is captured by the sensor that depends on the sensor size. So, if the amount of bokeh doesn't depend on the sensor size, why in this case should the f-number change?

    To me, 50mm f1.7 lens on the APS-C sensor should become 80mm f1.7 full frame equivalent.

  • Josh November 3, 2011 11:49 am

    Thanks everyone for the comments, as several people don't seem to quite agree over sensor size and it's effects on depth of field I'll try to further explain it here.

    Steve: You're exactly right about the circle of confusion staying constant regardless of sensor size. To picture crop sensors think of it more as phyisically cropping a photograph you've already taken, the depth of field stays the same but the equivalent focal length has changed by the factor of the sensor.

    In medium and large format, photographers have to use say, a 135mm lens will give an equivalent field of view as a 50mm in 35mm film, whilst at the same f/stop a 135mm will have a much larger physical aperture to keep the same fraction of the lens. Further using a 50mm lens would be equivalent to a wide angle, the circle of confusion has not changed however and the depth of field is the same as a 50mm in 35mm format. For this reason large format photographers often have to stop down to apertures such as f/64. Thank you for your comment

    Konstantin: The aperture will stay the same in relation to the light input and the circle of confusion which relates to aperture do not change when changing sensor size, however sensor size changes the equivalent focal length of your lens, in your NEX 3 this is by the factor of 1.6 times the focal length.

    Whilst the aperture stays the same, the equivalent focal length is now longer than it would be on 35mm film while the physical aperture, which affects the depth of field- has remained the same. Think also as I mentioned to steve, of cropping an image you've already taken.

    Now there are two factors in your Minolta lens which contribute to a shallower depth of field than the pancake lens, for one, the aperture is larger, at 1.7 as opposed to 2.8 on your pancake. Also the focal lengths are different, even at the same aperture the 50mm would have a shallower depth of field than the 16mm pancake.

    I'll do the maths here if it helps.
    Focal length (50mm) divided by aperture (1.7)= 29.41
    And for the 16mm 2.8= 5.71
    Now times focal length (50mm) by sensor factor (1.6)= 80mm (Equivalent field of view)
    And for the 16mm= 25.6
    Now divide the new equivalent focal lengths (80mm) by the apertures (29.41)= f/2.7
    and for the 16mm= 4.4

    So on your crop sensor bodies the depth of field and field of view is equivalent to a 26mm f/4.4 and a 80,, f/2.7

    I hope this has helped, thank you for commenting.

  • Eric Magnuson November 3, 2011 02:15 am

    ccting, yes, the shape of bokeh is due to the shape of your aperture rings as they close. In fact, by making a new "aperture" out of paper, you can change the shape. See this article on how to do it.

  • tjmurph9 November 3, 2011 12:44 am

    There's a very cool online simulation that allows you to play around with aperture and shutter speed settings and see the effect.


  • Eric Magnuson November 2, 2011 06:43 pm

    I'm sorry. When I said that you readjust the focal length, I meant to say you readjust the focus. Throughout the whole process, focal length remains constant. My mistake! After all, it's 2 am.

  • Eric Magnuson November 2, 2011 06:39 pm

    Great overview of focal length. Well done.

    One thing I'd add to this is hyperfocal focusing. I was going to write up something about it, but it seems like this article by Barrie Smith covers it well (he calls it hyperfocal distance, but it's the same concept).

    If you don't feel like reading the article, here's a quick overview. In essence, hyperfocal focusing is when you focus on something and then readjust the focal length (i.e., the zoom) of your lens to shift the depth of field (i.e., the range of depth of what is acceptably in focus). This is done because when you focus on an object, one-third of the depth of field will be in front of the object, and the other two-thirds will be behind the object. If you'd like more of the foreground to be in focus, you can shift the focal length to capture more foreground while at the same time keeping your object (and a large amount of the background) also in focus.

    This concept is used quite a bit in landscape photography to capture more foreground while not necessarily shooting at your lens' smallest aperture. As Barrie mentions in his article, a lot of people have a tendency to shoot landscapes at infinity, but this "wastes" some of the depth of field; you're focusing at an object at infinity, so one-third of the DOF is in front of this object, but the other two-thirds of it is lost to infinity. Instead, with the concept of hyperfocal focusing, you focus on the distant object, a mountain perhaps, but then shift your focal length. In the end, you'll have still have your object in focus but also more foreground.

    By the way, this is what the aperture marks on lenses refers to – you focus on an object, then turn the zoom ring to a closer focal length. As long as you keep the original focal length within the lines corresponding to your current aperture, your object will remain in focus.

  • Erik Kerstenbeck November 2, 2011 04:21 pm


    Here is another example of DOF control for Family Shots...wide open 70-200mm with availablbe light

    Pretty sweet


  • Josh November 2, 2011 01:52 am

    Thanks for the post!
    I came on just to check what was going on in the forums and had no idea my article would be on the front page, you've made my day.
    Also I hope it's not too much to ask if you could add my blog http://uvfiltermonocles.wordpress.com/ to the post, I write similar articles and am happy to contribute more here.

  • Paul November 2, 2011 01:44 am

    Loved the article. I have a question about depth and focal points. When you have a bigger aperture, and you are using the auto-focus mode on your camera, where does depth of field begin? Will it begin where your focal point is located and extend past your focal point? or is that the middle of your dof and a little in front and a little behind will be in focus? Any insight would be greatly appreciated. Thank you.

  • danfoy November 2, 2011 01:29 am

    Excellent article, thankyou. I think the most informative article I have read on DPS since I first came across it 3-4 years ago. More like this!

  • Shanmugam November 2, 2011 12:58 am

    Can some one explain how the focal length gets related to field of view. http://software.canon-europe.com/files/documents/EF_Lens_Work_Book_7_EN.pdf . PAGE 3 OF 20 .

  • Konstantin November 1, 2011 10:45 pm

    I am not sure I agree with your statement on crop sensors that F-number changes accordingly.

    The thing is the actual focal length of the lens (distance between the outer lens and the focal point as you've shown above) doesn't change. If the lens is 50mm f1.8 the focal length of the lens itself is still going to be 50mm. It doesn't change. Nor does the aperture change - it still remains at 27.7mm.

    What changes is the sensor size. The crop factor 1.6 just means that the sensor is 1.6 times smaller than the full frame, or, in other words, you could take the same shot using a full frame sensor and crop it by x1.6. The reason the focal length is re-calculated for smaller sensors by multiplying by the crop factor is simply to say that to achieve the same level of zoom on a full frame sensor the lens should have the focal length of 50mm*1.6 = 80mm.

    You would be right if the actual physical focal length of the lens changed from 50mm to 80mm and the actual physical aperture stayed the same 27.7mm - in this case, obviously, the F-number of such a lens would change as well to 2.8, but it's not the case with a smaller sensor.

    Also, if you were right, the amount of bokeh you would get using the same lens on a smaller APS-C sensor should be less than that on a full frame sensor, but it's not the case. An old full-frame 50mm f1.7 lens on my Nex camera gives me much more bokeh than the Nex f2.8 pancake. Please compare these images (shots not mine but with the same combination of lenses):



  • B. Jay November 1, 2011 05:32 pm

    Great article! Now I understand it all. I always wondered that why my point and shoot with F2.8 lens can't give a shallower DoF as F2.8 lens on a DSLR.

  • Dewan Demmer November 1, 2011 05:10 pm

    Depth of Field can be such a pain to explain, and then it just can get downright messy. Honestly I dont try to explain it, so cool for go at it.
    Here is a nice example of shallow DOP ( EXIF info is attached to the images )

  • Erik Kerstenbeck November 1, 2011 12:13 pm


    Wonderful article! I like to shoot wide open at times to get great Bokeh! These simple Maple Leaves changinging colors would have been boring with great DOF. But wide open at f2.8, they are magnificent!


  • Phoenix Photographer November 1, 2011 11:30 am

    Depth of field is one of my favorite visual "effects". Thanks!

  • ccting November 1, 2011 10:57 am

    I think we can control the shape of bokeh, right? I guess the shape of bokeh is influenced by the shape of blades that control the aperture.. Then placing the shape in front of the len with black form may change the shape, is that true?

  • ccting November 1, 2011 10:53 am

    Any technique that we tilt the normal dslr camera to gain better depth of view. I think decreasing the aperture more than f/8 usually (i.e. increasing the f-number) will lose its sharpest due to diffrasion?

  • Steve November 1, 2011 10:02 am

    If you are going to run guest posts can you please fact-check them first.

    This might be true in _some_ cases:

    "A shallow depth of field is highly sought after... and is found in many professional photographs."

    But is not a universal truism. Sometimes a greater depth of field makes the image.

    If you didn't give up at that point you only have to continue to the section about crop sensors to confirm your fear that the author doesn't know what they are writing about.

    For any lens of a given focal length, at a given aperture, the circle of confusion does _NOT_ vary depending on the size of the sensor.

    Spare us the pseudo-science please.

  • Chris November 1, 2011 09:57 am

    So, this may sound a little ignorant, but does that mean then that a 600mm Nikon f4.0 lens has an aperture of 12.5 cm? That's nearly 5 inches. Or do the really long lenses play by different rules when it comes to calculating aperture?

  • Snap November 1, 2011 08:25 am

    Good article, and your overall message is right... however, at a quick glance you have the aperture at the focal plane of the lens (i.e. at the sensor!), and you use the words "difficult to keep the entire bird in focus due to excessive depth of field" when really you mean "insufficient" i.e. "due to shallow d.o.f." etc.

    I know they're small nit-picks for people who understand this stuff, but it's very confusing for people who don't.

  • Nicole November 1, 2011 07:00 am

    Thank-you! I appreciate the explanation, especially as it applies to different sensor sizes. This was an "Ah Ha!" moment for me.

  • THE aSTIG @ CustomPinoyRides.com November 1, 2011 06:36 am

    Well said! I would like to add a few things to this as well, for an even "deeper look" into depth of field, particularly for the type of photography I do.

    I specialize in Car Photography and you'll see most of my work at http://CustomPinoyRides.com

    First of all, cars are large subjects. So, say positioned in a quarter angle, you may not want too shallow a depth of field as you might only get one part of the car in focus, whilst the rest of the car remains out of focus. What you actually want is proper background separation. So an aperture of say f/5.6-8.0 will keep the entire car reasonably sharp while the background can be out of focus depending on the distance from the subject. This analogy may apply not only to cars but other large subjects. It's about creating balance between keeping the subject (and parts of it) sharp, whilst separating it from the background.

    The second point which I would like to raise is that you mentioned depth of field is ultimately affected by (1) Aperture, and (2) Distance between Subject and Background. I think you missed factoring in a third point - Distance of the camera from the subject and background. Depth of field will be shallower (more bokeh) if the "distance between the camera and the subject" is lesser than the "distance between the subject and the background". Likewise, depth of field will be greater (less bokeh) if the "distance between camera and subject" is greater than the "distance between the subject and the background". This applies not only to cars but to all types of photography in general.

    Just my two cents. Thank you!

  • James Tiblier November 1, 2011 05:56 am

    Very well explained thanks for taking the time to make this diagram, I don't think I could have done it any better.