The wrong questions to ask when looking for photography advice

Earlier tonight, I saw the post below on photography group I am a member of on Facebook:

"Wanted: Advice for graduation photos! 24-70mm 2.8 or 24-104 f4? (outdoor photos)

FREE

Auckland, New Zealand

Advice needed please:(Admin delete if not allowed)

Shooting friends graduation(s) tomorrow (Tuesday 27th, - Uni of Auckland). __Currently using 5D MK II with 50mm 1.8
Q: Should I hire a 24-70mm 2.8 or 24-105mm f4?

Will be in daylight so ISO 100, aperture 2.8-4 and auto shutter (AV mode). Or different settings?

Ive been advised to use the 24-105mm f4 since daylight?
Your advice is much appreciated amazing people !

(I usually do street photos so not experienced in formal portraits)
Thanks people!"

While the question wound me up, the responses quickly saw me seeing red. Everyone (including professional photographers) focused on the equipment, suggesting that a different lens was required and would somehow make the resulting images better by virtue of being shot using the new lens.

That advice is garbage.

Any of the lenses would have been fit for purpose. Critically, this includes the 50mm lens that the poster already owned. What was missing here wasn't gear, it was an understanding of what the various trade-offs involved in photography are.

The 3 reasons to choose one of the zooms (and why they're not very good reasons)

One: Versatility - Wide Angles

In my opinion, this is the strongest of the reasons to choose a zoom lens. While the 50mm lens will be fine in most situations, if you are in a closely confined space or need to take photos of a large group, the ability to shoot at wider angles can be an advantage. However, as this person states they will be outdoors, the need for a wider angle lens can probably be removed/reduced by simply walking further away from the subjects (i.e. using sneaker zoom).

Two: Versatility - Perspective

The second strongest reason is based on personal preference/common practice in portrait photography. In most cases, photos taken with a telephoto lens are more flattering than those taken with wider angle lenses. If I had all 3 of the lenses in my bag, I would probably use one of the zoom lenses at 70mm+ to capitalise on this. However, if I only had the 50 and wanted a more telephoto look, I can achieve this for free by cropping the image in post.

Three: Technical advantages

There will be differences in the performance of the lenses. One may have 'better' bokeh, produce sharper images, have image stabilisation, etc. For reasons like these, one of the lenses will be the best choice on paper. However, all of the lenses should produce acceptable images and, if we're being brutally honest, it is unlikely that the friends will be able to spot any difference that would be attributable to lens choice alone. If we're even more brutally honest, it is unlikely that the photographer will be able to spot these differences themselves either.

The 5 reasons why the 50mm lens would have been perfectly fine

One: They already own the lens, so they should know how it behaves

In order to know and take advantage of those technical advantages mentioned in the previous section, you need to be familiar with your equipment. If you're hiring a lens for a day you'll either have no real idea of how it behaves or you will be trusting the advice of someone else. Either way, really, you've taken the control out of your hands. In addition, you're more likely to make a silly mistake with a lens that you're unfamiliar with (zooming the wrong way, accidentally disabling autofocus) and less likely to know how to fix any issues that come up. Time you spend dealing with these issues is time you're not spending attending to/capturing moments happening around you.

Two: Outdoor photography is 'sneaker-zoom' friendly

As mentioned in the first point of the previous section, when you're outside the ability to zoom in and out becomes far less important. If you want to 'zoom out', walk further away. If you want to 'zoom in', get closer. Use your environment to save your money and expand your options.

Three: Depth of field (the extent to which the background is in/out of focus) is controlled by factors other than the lens

One of the main reasons people shoot portraits with telephoto lenses is the ability to 'blur' the background by throwing it out of focus. As I said earlier, If I had all 3 of the lenses in my bag, I would probably use one of the zoom lenses at 70mm+ to capitalise on this. 

However, while focal length is one tool in the toolkit here, larger apertures and/or greater distances between the subject and the background also allow photographers to blur the background. As the 50mm lens has the widest potential aperture setting and the shoot will be taking place outdoors, a blurred background is well within reach with a 50mm lens.

Four: Cropping control - Benefiting from a telephoto like perspective

One of the other reasons that people tend to use telephoto lenses for portrait work is that telephoto lenses compress the foreground and the background. As a general rule, this tends to make people more 'photogenic'. However, it isn't actually the lens that is doing the work here, it is the distance between the subject and the camera. You can achieve the same compression by shooting an image that is wider than required and cropping down in camera/in post. 'Crop sensor' dSLRs essentially do this all the time.

Five: THEY ALREADY OWN THE LENS

While they absolutely can hire one of the other lenses and one of the other lenses may give them photos that are closer to what they are picturing in their heads, hiring another lens costs money and time. Applying an understanding of how photography works can save both of these. Developing such an understanding is well worth the investment.

The best advice

Equipment doesn't take good photographs, you do. 

You can sink as much money as you want into 'the right' gear but spending that money won't make you better at planning and composing a successful photograph.

Learn the underlying principles and apply them everywhere.

The most concerning lines in the original question were these ones:

"

Will be in daylight so ISO 100, aperture 2.8-4 and auto shutter (AV mode). Or different settings?"

- This is concerning because the 'right' settings will vary by the amount of light available in the specific location at the specific time and the intended result.

"Ive been advised to use the 24-105mm f4 since daylight?"

- This is concerning because the focal length is irrelevant if the light available is the primary concern.

"

I usually do street photos so not experienced in formal portraits"

- The principles of photography are the same regardless of the type of photography you are doing. 

Know what you're going to shoot before you shoot it

What was missing from the original question (and subsequent advice) was a clear indication of what they wanted their images to look like. While anyone can (and plenty did) throw a combination of focal length, shutter speed, ISO, and/or aperture out there, each combination will be making a different set of trade-offs resulting in a different final image. Rather than entering a bunch of numbers into a machine and hoping everything works out, learn what the numbers mean and set them to what you want so you get what's in your head.