For years, I believed focal length played a major role in depth of field for portraits — and I made creative decisions based on that. Turns out… I was wrong. In this video, I’ll break down what actually controls depth of field, run a real studio test, and show you how to use DOF intentionally to create stronger portraits.
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We’ll cover:
What depth of field really means in practice
The four factors that define DOF (aperture, focal length, subject distance, sensor size)
Why aperture is your biggest creative lever
My full mannequin test from 35mm to 200mm
The truth about focal length and DOF in portrait photography
How distance changes everything
The 1/3–2/3 rule (and when it doesn’t apply)
Hyperfocal distance explained
Why diffraction can ruin sharpness at small apertures
Whether you’re shooting portraits in the studio, working outdoors with shallow depth of field, or just trying to figure out why your photos don’t look the way you expect — this video will help you master DOF once and for all.
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Gear:
Canon R5 Mark II
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Canon RF 28-70mm f/2.0
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Canon RF 85mm F1.2 L USM
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📌 Chapters
00:00 – Introduction
00:22 – How I got things wrong
02:26 – Defining DOF
03:05 – What goes in to Depth of Field
03:24 – Aperture
06:23 – Focal length
07:14 – DOF Test Results
08:43 – Distance to the subject
09:54 – 1/3 – 2/3 rule
10:48 – Hyperfocal Distance
11:42 – Diffraction
12:55 – Final Thoughts
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#PhotographyTips #DepthOfField #PortraitPhotography #PhotographyTutorial #LearnPhotography #Aperture #FocalLength #PhotographyMistakes
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Comments
28 responses to “The Truth About Depth of Field in Portrait Photography (I Got This Wrong)”
Just because of lacking DOF scales on most Canon optics I never chose for Canon.
Nowadays I mostly use classic Zeiss and Voigtlander lenses, all manual focus, on my D850.
Classic lenses are less perfect and have character. Character is missing on (ultra) modern lenses that are too clinical perfect.
Great video. John, it was a pleasure to shoot with you last year. I’m need to make another trip to Chicago soon to see you.
For corporate/commercial headshots, my default has always been f/8.0, giving me a sharp/crisp head from the tip of the nose to the back of the side of the head. I use the Canon 70-200/f2.8 zoom. If I recall, John also mostly shoots at f/8.0 in the studio.
It is aight to be mistaken sir
Distance to subject matters a lot in portraits, but not primarily in terms of depth of field. If you are too close, the nose will look too large, and the ears might look small. For a head shot, you want to be over 8 feet from the subject. The reason that people use 85mm or longer lenses for portraits with full frame is that puts the camera 8 or 10 feet from the subject. Then you choose the depth of field by setting the aperture. For other sensor sizes, you choose the focal length that does the same thing for subject distance, maybe 55mm for APS-C and 105mm for medium format.
Love your content John!
I want to know how to aim the light head at the object
Great points, and I appreciate that you avoided the silly "REAL professionals never use wide apertures" rhetoric. It's a tool, nothing more.
Very interesting and very useful
Let me help you understand this a bit better…. Let us say that you found that the perfect exposure on your full frame camera had the settings of 50mm, f4, 1/500s, ISO 200…. Then if you were using a Medium Format (Crop Factor 1:0.83) then the same depth of field would be achieved at the same distance to subject if you used a 60mm f/4.8 with the same iso you also need to adjust shutter speed to 1/600s…. Likewise if you used a M43 camera you simply use a 25mm, f2, 1/250s to keep the iso the same…. However! If you use the SAME EXACT LENS on all three cameras then you must adjust distance to subject AND IT IS THAT that will cause a significant challenge to keeping the depth of field the same…. Still it can be done!
Diffraction-limited aperture affects different optical formulas differently. Generally, the larger the throughput, the more forgiving the system can be. That's why even f/22 is usually perfectly usable on Phase One (medium format), yet it would appear totally mushy on an APS-C sensor. When the megapixel count is the same, a quick way to determine the desired results is by simply applying the crop factor. For example, if you know that f/8 is perfectly acceptable on a 24 megapixel APS-C camera, you should expect similar results on a 24 megapixel Full Frame camera at f/13.
APS-C create similiar look on f2.6, like FF on F4. It 1.5x difference, just like crop. Same with "Large Format" in GFX, or bigger Medium Format in "big" Hasselblads and Phase One. You need to calc based on sensor size difference.
I have actually seen the advice, "shoot wide open all day" from a rather popular channel. Even if possible, somewhat ignores the opportunity of other artistic choices in composition. Also, even with great sharpness wide open, the same lens will likely be sharper at F8.
BIG THUMBS UP FOR THIS VIDEO! Thanks for your review about DOF… HG from Chicago
Sensor size has no effect on depth of field. Another big mistake you need to correct.
The term ‘depth of field’ is something of a misnomer. There is only one plane, not necessarily flat, that is truly in focus for any given situation. Altering the various parameters (focal length, distance, aperture) has an effect on the circle of confusion and what appears to be in focus. A more accurate term would be 'zone of acceptable sharpness'.
Integrity. Thanks. A commodity not found too often any longer.
It's interesting that focal length doesn't affect depth of field as much in a technical sense, but given that it has a LARGE impact on 'compression' in an image — which affects the overall perceived bokeh — it's easy to include it more strongly into a practical application of techniques to achieve a blurred background.
another mistake is a long intro
OMG! I only now noticed that some of my lenses DON'T have the distance/depth of focus scale! Or any scale at all! I've been so accustomed to them I've just been taking them for granted. When you said "modern auto-focus lenses we lost those scales" I ran to my equioment only to make this shocking discovery. This sucks!!!
When my dad explained photography to me in the 70s, depth of field was a resource. You could use higher ISO film at the cost of grain, open your aperture and sacrifice DoF, or lslow down your exposure and risk motion blur. Only the last decade or so a near zero DoF is being marketed as a good.
Thanks John, for getting this straight – it's always a blessing watching your videos! To note: depth of field and hyper focal distance is depending on the sensor pixel density, too. Higher pixel density equals smaller depth of field when the expectation is to get the full sensor resolution projected sharp.
I’ve been arguing with people over this for years. Focal length isn’t a factor if the subject is the same size in the frame. Thank you.
I appreciate the probity. Thanks John! This strengthens our community.😎
One of the things I like best about your content is that, on top of great artistic skills, you get the technical details (mostly) right. I recently gave a talk on photography settings to a group of engineers, so I had to get this right to the tiniest detail, here are some comments to your explanation:
* In line with what @comeraczy2483 pointed out, the formula you are using is an approximation valid when the distance is neither very small, nor close the hyperfocal distance, and in that setting the transversal magnification can be approximated as m ~ f / u, and DoF ~ 2Nc / m^2. Magnification is size on the sensor divided by real world size, so it's a proxy for framing, as you showed in your experiments. The results for wider groups start to diverge from the constant-ness of DoF because we start getting close to the hyperfocal distance.
* Bokeh size does depend on focal length directly, even if you keep magnification constant. If you are focusing on a subject at a distance u and the background is very far away, at infinity, a point source will become a circle of diameter C∞ = f m / N on your sensor, so if you keep the framing, and thus m, the same, doubling the focal length will have the same effect as halving N, i.e. 2 stops of aperture. if the background is closer, say at a distance uB, then the theoretical bokeh size is (1 – u/uB) C∞.
Great video, thanks for sharing!
Thanks a lot for this video. I think that it is a honest mistake because that DOF formula is misleading because it uses quantities that have hidden relationships, and this leads to some terms being squared (in particular f and u) giving the incorrect impression that they are super important. However, if you look at the quantity u/f, it is indicative of the field of view, and, as you demonstrated experimentally, keeping the field of view constant implies keeping u/f constant, and therefore keeps the DOF constant. The DOF formula can indeed be rewritten independently of u and f, using the transverse magnification M instead (M=f/(u-f)): DOF=2Nc(1-1/M)^2. Still misleading because of the squared term though.
Another way to rewrite the formula is to use the relation N=f/D, where D is the diameter of the aperture. This means that N/f^2 can be re-written as 1/DF and the formula becomes: 2cu^2/fD. Using M, this becomes 2c(1-1/M)u/D. At that point, the formula is a lot more useful because it expresses DOF in terms of 3 physically meaningful quantities (u, D, and M) and each contributes to the DOF to the same degree (none is squared).
All that said, with modern lenses that implement some form of focus breathing compensation, the focal length at short focus distance isn't the same as at infinity, and the DOF formula must be re-written accordingly.
Intriguing that even someone that has been shooting as long as you have with incredible pictures realizes they got something wrong.
Always amazed at how weak my technical understanding is when I watch one of your videos. Great content. Stopping down has been one of the things I have concentrated on in my portrait work. I have had nose tip out of focus, Eye sharp and ear out of focus and it can be really frustrating. F11 seems almost like a sacrilege to me in the studio but then I realize how many great portraits in history are shot at that stop