Archibald wrote in post #19298278
Will the subjects be sitting down for the photos, in a suitable place? Or will you photograph them as they are standing and moving around? Do they want full length or head and shoulders? These things can make a big difference to how you do the work.With the 100mm, you might be fairly far from the subjects. You should try some tests to check what the distance will be. You might have to shout at them to communicate.
A diffuser like that will give slightly better light, but will reduce the brightness. But that might be ok. You should do tests. The closer the light is to the subject, the brighter and softer the light. But when you are close, you might have light falloff problems.
As I stated earlier, "Classic head & shoulders shot taken with 100mm lens at about 10' from subject, avoids perspective distortion caused by too-close subject distance."
If trying to shoot full length with 100mm, That needs more like 19-20' distance to get about 7' of height into the shot into a FF sensor.
It is better to suit FL selection to framing, rather than alter your shooting distance...keepi yourself about 10' away from the subjects. Leave the longer distance stuff to the fashion shooters or the candid shooters who are too shy to approach their subjects on the street. It is harder to keep people from walking into the space between you and the subject when you are 10' than when you are 20', as well!
The issue of 'light falloff' is worse when the subject lighting is CLOSE.
- If subject is 4' from the light, things which are 8' from light (4' behind subject) are illuminated -2EV dimmer
- If subject is 8' from the light, things which are 12' from light (4' behind subject) are illuminated about -1.2EV dimmer
- If subject is 16' from the light, things which are 20' from light (4' behind subject) are illuminated -0.66EV dimmer
So you can use this to advantage if the background is somewhat cluttered and distracting...you want more falloff to help reduce the distraction.
OTOH, if the background helps set the scene, to show location of the event, you want less falloff so the background is captured somewhat subdued compared to your subject, but not dark.