choosing a prime lens to go with a kit zoom

[William W]

Are you talking about doing this to avoid showing too much distortion due to the wide angle lens?

Yes.
I am talking about MINIMIZING the effects of (mainly) BARREL DISTORTION and FORESHORTENING and KEYSTONE DISTORTION when using a Wide Angle (rectilinear) Lens for Portraiture.

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[comments about the] 16mm f/2.8 lens for portraits :
"It's certainly not a great choice for photographing friends or family on a day out; because of its short focal length, that F2.8 aperture isn't going to give you significantly blurred backgrounds, and the inevitable wide angle distortion means anyone towards the edge of the frame will look unflatteringly fat."
Are you talking about the same effect?Are you talking about doing this to avoid showing too much distortion due to the wide angle lens?

Yes. Exactly. I am talking about Minimizing the effect.

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Some general info, but only about these particular issues we are discussing with respect to using W/A Lenses for Portraiture:

I am not keen on using the phrase “Wide Angle Distortions”, because it is a non technical and a generic phrase which dissolves all the elements of what I am talking about, into a mishmash which then leads to unclear explanations.

That stated what I am talking about are these issues below . . .(Underlined and Bold are key words which can be further researched):

Firstly, we are discussing a Wide Angle Rectilinear Lens to be used for Portraiture.

Secondly, most of these lenses will suffer from Barrel Distortion

Thirdly, what is often generically termed as “Wide Angle Distortion” is usually either (in no priority):
 Foreshortening
 Barrel Distortion
 Key Stone Distortion
And MOST USUALLY a combination of all three.

Fourthly, Perspective is determined by the Camera’s Elevation to and distance from the Subject (i.e. Perspective is determined by the Camera’s Viewpoint) and NOT the Focal Length of the Lens.

And fifthly, some of these distortions can ‘corrected’ quite adequately in Digital Post Production: but having cut my teeth with Film, where it is a lot more difficult wedging the Print Paper’s Masking Board at various angles and bowing the paper to ‘correct’ these issues in the wet darkroom – one becomes skilled at ‘avoiding’ that type of work . . . and for less digital post production work - it bodes well to get the image as ‘good’ as possible SOOC (straight out of the camera).

***

A really quick demo -

These are various shots of the same scene made with a 16mm lens used on an APS-C Camera – all the images a full framed crop and are SOOC only resized and sharpened for web display.

For the first group of shots, consider the ‘Blue Wall' and all contained on it, as "The Subject".

In this first shot the lens’s axes are perpendicular to the blue wall. Note that the picture frames (top left) suffer from a little barrel distortion, but to most eyes, both would arguably be “reasonably acceptable” as they do look reasonably rectangular –

Also – another point about this image is the Camera Elevation is at the midpoint of the height of the blue wall and also the Camera’s Viewpoint is situated in the middle of the sides of the blue wall. This point is important when making a Portrait Group Shot with a very W/A Lens – more on this later.

*

In this second image, the camera has been moved such that the lens is looking across the Blue Wall and also the Camera has been moved to Camera Left and the Elevation is now at the Photographer’s Eye Height (well above the midline of the wall):

Notice now the top left picture frame is quite obviously skewed the top left corner appears being ‘pulled’ upwards and outwards.
The same is true of the large picture frame at camera right but it is not as obvious – more on this point later.

*

Now let’s move from the Blue Wall as the Subject and make a Portrait.
We will pose the Subject in the middle of the frame and will make the Camera Elevation at the Subject’s mid height – just about at belly-button level.
In this Portrait the Subject is represented in correct proportions.


*

Now we will dolly (i.e. move in a straight line) the Camera to Camera Left: but still keep the same Camera Elevation such that the Subject now represents -‘anyone towards the edge of the frame [who will] will look unflatteringly fat’.

There is a point to note – if there is a group of People, obviously the Camera Lens can ONLY be perpendicular in BOTH axes with the CENTRE Person – BUT the Angle of Skew can be limited by not placing the end person – right at the frame edge, such as in this example:


Note that there is little or no difference in the Subject’s resemblance in this and the previous image. Note especially the comparative proportions of the Head, Shoulders and Bottom.

This collage will make the comparisons easier –


*

But these two images below will show how easy it is to make disproportionate people, at the edges –

In this first image we lift the camera to eye height and skew it across the imaginary line of the group of people and in this example the ‘end person’ is far away from the camera –


Note the Subject’s bottom although not linearly very different in size with respect to the whole the frame – yet the Bottom appears much larger in proportion to the Subject’s body – hence the Subject appears ‘fatter’: this is a result of both Foreshortening and also Keystone Distortion – and NOT all that much Barrel Distortion.

This is because the Camera’s Elevation (now at about the height of the Subject) and because the lens’s axes is skewed across the Subject the Subject’s Head is closer to the camera than her Waist and Bottom and those lower areas of her body are ‘squished out’ in a ‘Keystone’ and also appear ‘squat’ or ‘short’ relative to the head, because of the Foreshortening.

*

Here is the appearance of the ‘end person closer to the camera’, when the lens’s axes is skewed to the Subject.


Note here how the Barrel Distortion ‘pulls’ the Head and Shoulders and also note how the Foreshortening and the Keystone Distortion still renders the lower Waist and Bottom body ‘squished’ and thus ‘fatter’ - even though the Shoulders appear much wider than in the previous images.

WW

Footnote:
I have shot a few Weddings.

As a matter of course I had a ‘Rule for Group Portraits’, which was - “Never to use a lens wider than FL = 35mm” (on 135 format).
This would be the equivalence of FL = 23mm on your Sony Camera.

The reason I had this rule was, because when shooting under the pressure of time it is really so easy to go wider and skew the lens’s axes just a little bit and end up with what I termed “fat arms at the edge syndrome”.

Obviously (in the days of Film) ‘Print Sales’ were a Wedding and Portrait Photographers’ living and what put bread on the table – hence to eat, I had my ‘Rules’ which everyone obeyed.

Outlined above are some preliminary methods of disobeying those rules and not always being caught.

[spetsnaz26]

Yes.
I am talking about MINIMIZING the effects of (mainly) BARREL DISTORTION and FORESHORTENING and KEYSTONE DISTORTION when using a Wide Angle (rectilinear) Lens for Portraiture.
.

eh...Bill, that's an epic level effort there. I just can't thank you enough. I have some idea about your advice now and will check out those three types of distortions closely.