Human Body Framing - DoF Cheat Sheet

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Originally Posted by Stagecoach

Dem, I will add the 'subject distance' for each scenario of full, 1/2, 1/4 & 1/8th body framing for the three FLs of 100, 200 and 300mm.

I will not go to shorter FLs because this is then more within the realm of close up portrait work.

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and this is exactly where I was coming from, hence the confusion.

If you are shooting sports with a zoom lens, you only concentrate on framing your shots which automatically takes care of the fl/subject distance business. So this information might not be very useful in your scenario, unlike in portrait work where you always want to be about 2-3 meters away from the subject and need to know which prime lens to use for which framing. For example, 35-50 mm for full body, 70-85 mm for half body and 100-135 mm for head close up shots. This is probably a different cheat sheet though :).

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Originally Posted by dem

If you are shooting sports with a zoom lens, you only concentrate on framing your shots which automatically takes care of the fl/subject distance business.

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Agree, but, for some it may be useful to know if their zoom or fixed lens at its max FL is capable of getting say a full height shot of someone at the other side of the pitch from where they are positioned as they put that penalty in:)

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Originally Posted by Stagecoach

Ted, I find these small differences on various DoF calculators I have used and tend to ignore them. A lot depends upon the CoC that has been used.

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Quite so. The CoC in the spreadsheet is calculated for my 1280x1024px monitor and the diagonal of my camera sensor, making the magic number used for DOF calcs 1/1600. In other calculators an 8x10 print is often assumed. And for a 1:1 macro shot the CoC doubles compared to 1:infinity - not that that is particularly helpful, there being next to no DOF in a 1:1 shot anyway.

I originally wrote the spreadsheet for table-top close-up work, where the magnification can make a big difference to DOF and where it is often important to get the whole subject in focus. From that POV it is nice to enter the 'framing' so to speak and be told the shooting distance and the DOF for various f-numbers.

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To be honest I have never used a DoF calculator for 'accurate' readings because I believe that in real world photography 95% of the time it would not be possible to take an 'accurate' reading of the subject distance. But they are important as they give you a reasonable indication of what to expect.

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Indeed. Whenever I step out into the Real World, I use pure guesswork ;)

Good luck with your cheat sheet . .

What an interesting, educational thread which is both good natured and humorous in parts.

Hi Grahame,

I have a couple of suggestions for relating to the presentation of the figures on the diagram in your initial post, this one;

http://i60.tinypic.com/rbkrvr.jpg

If I were producing this, I would use more appropriate units for the DoF figures than (whole) metres, which dictates lots of decimal points and leading zeros, which (for me at least) mask the clarity of the relationships between the numbers. The cm (centimetre) would seem appropriate as the smallest figure is 1 cm (vert. framed tight head at f/2.8) and the largest is 1065 cm (horiz. framed full length at f/11).

For the figures on the right hand column; you could stick with metres (perhaps using "m"), although I'd suggest rounding most to two or three significant digits, although (to my mind) these would also 'work' in cm. Indeed, it may 'help' some people if the units don't change.

Just my tuppence worth = 0.02 GBP :D

By the way, I have already found it useful, I now know that if I were to shoot a group of full length people in horiz. framing at f/11; the DoF (at 1065 cm) should be sufficient for several rows of people to be 'sharp' (as long as I am careful focus to use the DoF to best advantage).

Thanks,

Hi Dave,

Fully agree comments regarding the 'units'.

Personally, I was forced to change from imperial to metric when quite young and continued throughout my engineering career with just the use metres and millimetres. To this day I never work or think in centimetres but understand many do as my daughter would confuse me when she was at school with the term 'cm':)

I'm going to start work tonight on a spreadsheet version of which hopefully units may be selectable.

Grahame

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Originally Posted by dem

. . . unlike in portrait work where you always want to be about 2-3 meters away from the subject and need to know which prime lens to use for which framing. For example, 35-50 mm for full body, 70-85 mm for half body and 100-135 mm for head close up shots.

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Why?

That is - What are your reasons for always wanting to shoot Portraits at a prescriptive Subject Distance range?

WW

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Originally Posted by Stagecoach

Hi Dave,

Fully agree comments regarding the 'units'.

Personally, I was forced to change from imperial to metric when quite young and continued throughout my engineering career with just the use metres and millimetres. To this day I never work or think in centimetres but understand many do as my daughter would confuse me when she was at school with the term 'cm':)

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As did mine, Grahame,

In the early 70's our Company metricated and then produced manufacturing drawings for the new product - a ground-based gas turbine (Ruston Tornado). The story goes that nobody told the shop floor which still had all its Imperially scaled machines, standing ready for action . . .

Even further OT is my favorite Casio calculator that does fractions - perfect for woodwork over here :D

Well finally found the time to work on the chart so here's an upgraded version.

It's now on a spreadsheet so very easy to change the units from metric to imperial and whatever divisors.

http://i58.tinypic.com/donq89.jpg

I have added the subject distances for the framings using three focal lengths chosen simply because 300mm is the max I have:)

Any suggestions or comments are welcome of course.

Grahame

Now that the depth of field table is all sorted, I have a converse problem related, for example, to my photographing a banana flower a little while ago. The flower was about 2metres away and filled the height of the picture (full frame camera in landscape mode). The background trees were about 6 metres away. How small does the depth of field need to be for the background to be creamy smooth? I didn't manage to get a combination of a sharp flower and suitably blurred background.

Graham, thanks for posting this. Now, a stupid question: what does "mtr" stand for?

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Originally Posted by Cantab

Now, a stupid question: what does "mtr" stand for?

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meters, Bruce, at a guess.

In Canukistan, it would written as 'm' ;)

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Originally Posted by TonyW

Now that the depth of field table is all sorted, I have a converse problem related, for example, to my photographing a banana flower a little while ago. The flower was about 2metres away and filled the height of the picture (full frame camera in landscape mode). The background trees were about 6 metres away. How small does the depth of field need to be for the background to be creamy smooth? I didn't manage to get a combination of a sharp flower and suitably blurred background.

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Tony,

If I understand your question correctly the priority here would be in selecting an aperture that gives you acceptable DoF for the flower and the background is then determined for you.

The resulting background blur will be due to a combination of the aperture you had to use, the distance from subject to background, lens specific characteristic and to a degree the focal length used.

The DoF table in the below link will give you the DoFs at subject distances, focal lengths and apertures for any camera sensor size.
http://www.tawbaware.com/maxlyons/calc.htm

Grahame,

Nicely charted. I have a friend who does sports photography and she would find this most useful.

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Originally Posted by Shadowman

Grahame,

Nicely charted. I have a friend who does sports photography and she would find this most useful.

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Feel free to use or give it to anyone John.

If there's no suggestions for reasonable changes I will post one tonight in Feet and Inches for those not yet moved into the modern world of metrication or dual use like myself:)

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Originally Posted by Stagecoach

Tony,

If I understand your question correctly the priority here would be in selecting an aperture that gives you acceptable DoF for the flower and the background is then determined for you.

The resulting background blur will be due to a combination of the aperture you had to use, the distance from subject to background, lens specific characteristic and to a degree the focal length used.

The DoF table in the below link will give you the DoFs at subject distances, focal lengths and apertmures for any camera sensor size.
http://www.tawbaware.com/maxlyons/calc.htm

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Grahame, I think I understand the general principles but I am trying to quantify the degree of blur needed for the background. I haven't got my head around it yet but it might as simple as requiring that the ratio of the distance of the background from the main subject to the depth of field be greater than a certain number.

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Originally Posted by TonyW

Grahame, I think I understand the general principles but I am trying to quantify the degree of blur needed for the background. I haven't got my head around it yet but it might as simple as requiring that the ratio of the distance of the background from the main subject to the depth of field be greater than a certain number.

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Tony, I think I know what you are getting at but the question I ask myself is how you quantify blur.

You mention 'the degree of blur needed' but whilst we can determine and measure such things as distances, aperture and DoF how do you define 'blur' to a size?

I look forward to others views on this one and will ponder over it based on the following;

For a given subject (lets say a head) with a fixed background distance and shot from both near and far, but framed the same by using different focal lengths, the image taken from the farther distance has a background that appears 'blurrier' but DoFs for both images are the same.

I have come across this tonight regarding background blur/bokeh, it may be of interest to you Tony.

http://www.bobatkins.com/photography...ound_blur.html

We then get into the realms of the fact that using different FLs (same framed shot) have a different affect on near or far backgrounds:eek:

I am at the moment, doing some preparation for shooting orchids in a controlled condition and interested in your question above about quantifying blur -- and given that the distance, dof and framing are the same, and the distance position of the light source do not change either, not using different focal lengths as you indicated above, I found that the larger the light source relative to the subject, the softer the light will be or blurred in the background. So to me, it is just a matter of changing the position of my diffusion material to achieve the right blur of my background. Does this thought count?

Hi Izzie, I think not. What you are doing is just changing the brightness of the background, but, I suppose the darker or brighter it gets there is less contrast and hence definition of the background.

Grahame

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Originally Posted by Stagecoach

Hi Izzie, I think not. What you are doing is just changing the brightness of the background, but, I suppose the darker or brighter it gets there is less contrast and hence definition of the background.

Grahame

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Oh, OK...I hope someone else can pitch in too so I can learn something...so I am bumping this thread...

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Originally Posted by Stagecoach http://cdn.cambridgeincolour.com/for...post-right.png Hi Izzie, I think not. What you are doing is just changing the brightness of the background, but, I suppose the darker or brighter it gets there is less contrast and hence definition of the background.

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Originally Posted by IzzieK

Oh, OK...I hope someone else can pitch in too so I can learn something...so I am bumping this thread...

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Izzie: I have found that, for table-top work - especially watch shots, the relative positions of the subject, lamp and diffuser do affect contrast, just as Grahame suggests. After all, that is the purpose of diffusion - to attempt to bring the scene dynamic range within the bounds of the poor old sensor.

Going to extremes:

1) If the lamp is close to the diffuser but far from the subject, the lighting tends to a point source - giving specular highlights. 2) On the other hand, if the lamp is far from the diffuser and the diffuser is close to the subject, the lighting tends to be a Lambertian surface - reducing specular highlights.

Examples are 1) a flash with a tiny diffuser pointed straight at the subject. 2) a big sheet of cloth or tracing paper near the subject with a remote flash some distance away.

In table-top photography however, the background may be far from both the subject and the lighting. Therefore, the bokeh may still behave in a more specular manner or have more contrast. On the other hand, a background closer to the subject may not.

Naturally, the separation of the background from the subject affects the choice of aperture, so round and round we go . . .

As to quantifying bokeh, perhaps we should consider a point source in the background and assess it's shape but, more importantly, measure the pixel size of the resulting bokeh 'circle' which, I would have thought, is a case of 'the bigger, the smoother'?

I am no purist, BTW. For a flower shot, as long as the background is blurred and generally darker than the flower, I'm a happy camper.

[totally OT: what does "G'lock" mean in your signature? :confused:]