When to use diffuser, reflector, fill flash and ND filter?

Question

This question stems from the answers I received for another question "Is 35mm on a cropped sensor good for fashion photography?"

I have been watching couple of videos where the photographer uses a HSS fill flash to take pictures and the images turn out looking stunningly amazing. For example this video on youtube "Creating Color with Off Camera Flash"

The photographer demonstrates how that the images look flat when the images are taken with just natural light while the pictures taken using flash have good color tones and depth. I wanted to try this approach but then soon realized that my Nikon D5600 (with 50mm 1.4G) does not support HSS.

I started to look for workarounds and found this video High Speed Sync vs ND Filters where the photographer shows that ND filter and HSS flash both can achieve same results.

In other tutorial videos, the photographer simply uses a diffuser and reflector. But most of the time I see the reflector and diffuser being held by a person.

I want to understand when to use diffuser, reflector, ND and fill flash ?

Also If I use spot meter on the shadows of a person's face while I have the ND filter on, then is it a replacement for diffuser and reflector ?

Answer 1

ND filter and HSS flash both can achieve same results

That is a bit oversimplified. ND-filters ^{(ND stands for "Neutral Density", which basically means that they [ideally] filter out equal amounts of all visible wavelengths)} simply reduce the amount of total EV that your camera gets - with the same settings than before, your picture will become darker.

HSS on the other hand is a flash-/camera-feature that allows for higher shutter speeds while using the flash.

When you need a flash light but also want to stop high-speed action, then an ND-filter will not help you. If, however, you just want to get the exposure right and the flash sync time ^{(usually around 1/200s ± 1/3 EV)} is plenty fast for you, then ND-filters of course will work.

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Reflector | fill flash | ND-filter:

• Reflectors are a way to bounce ambient light (e.g. sun, but also flashes or other lights) to a certain region - like a mirror, but less harsh (though there are silver reflectors that are quite mirrory). You use them to lighten up shadows, emphasize regions of interest or add some colors (e.g. by using golden reflectors).

  • Pros: Continuous (as in: no flickering); don't need batteries; cheap
  • Cons: Bulky (especially in windy situations, you will need an assistant); efficiency depends on environment (i.e. don't work too well in new moon nights, if shooting in line with the sun,...)

• Fill flashes are a way to add additional light to the scene. With color filters and flash formers (like soft boxes), they can be used pretty similarly to reflectors.

  • Pros: High level of customisation (many different levels of power output, many different light modifiers,...)
  • Cons: Depend on batteries (bring plenty!); Not continuous, so they need to recharge between shots; need to be synced with the camera's shutter.

• Diffusors are a way to soften down harsh light. They can be useful to reduce shadows, but the diffused area is darker than the surrounding area.

  • Pros: Cheap (typically come with reflectors)
  • Cons: Same as reflectors; Darken the diffused area

• ND-filters, as stated above, simply darken the whole picture (an exception are gradual ND-filters, which only darken down a portion of the frame (they are mostly used to darken the sky in landscape shots). I would not consider ND-filters to be in the same category as the above mentioned light modifiers, because ND-filters at least do not directly affect shadows or other attributes.

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When to use what?

It might be just me, but whenever I work outdoor, I bring all of these with me and choose them according to the situation: There are situations where I use none, there are situations where I choose just one option, and there are situations where I use all of them.

I will search around for a few tutorials on when to use which later (will include them here).

Basically, use whatever you feel most comfortable with at any time - there is no "right" or "wrong" in this (well, using a reflector in pitch darkness isn't the smartest move, but I think you get the point).

Personally, I like to use reflectors over flashes when the situation allows for them - they allow me more flexibility on my parameters. Then again, if I have to work alone, I tend to use off-camera flash(es). I rarely use an ND-filter in portrait photography, but rather use a polarizing filter if there is any use for it (e.g. they are useless in completely overcast skies). On some occasions, I use diffusors, but if you use relatively small ones (diameter below 3m), then they only work in certain situations because - as said - they darken the subject below them quite noticeably.

All of the options work better with an assistant that can help you to reposition your equipment: E.g. it can be really frustrating and exhausting to move between the equipment and your camera multiple times just to get a nose shadow out of the way.

Answer 2

The answer... Use whatever you have.

(Forget ISO for now) The main line of reasoning is:

1. If you want bokeh or shallow depth of field you need a wide aperture.

2. If you use a wide aperture you need a fast shutter speed.

3. If you want some directionality in the light you need additional light than the ambient one. Here we have some options.

a. Use a flash, but you normally have a limitation o the sync speed of the camera (see point 2).

b. So you can use an HSS flash, which is a series of bursts of the flash emulating a continuous light for a fraction of a second (avoid point a).

c. Use a video light (continuous light)

d. Use a reflector to redirect available light, for example, sunlight (continuous light).

e. Lower the ambient light so you still can use the wide aperture, but lowering the needed fast shutter speed matching the sync speed of your camera.

For example, the normal reading using your f aperture is 1/2000 you can need to lower the ambient light so your camera reads 1/200. Then use an ND filter of 10x. Now your ambient light is properly exposed at f aperture and 1/200. Now set up a normal flash.

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A diffuser is used for something different than changing the intensity of the light. It is normally used to... you guessed it... diffuse the light so you do not have a harsh light... but a diffused one.

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f. There is is a really interesting thing... there is a cinematography technique called "Reductive Lighting".

In some cases where you are lighting an interior scene, with a door opened, for example, yes, you could add a lot of lights to the interior so when the door opens there is not too much difference in the exposition.

But the reductive lighting technique is adding a black fabric, so it lowers the amount of light entering through the door! So yes, a "diffuser" can be used in some situations to lower the amount of light hitting a subject.

All are tools to level the exposure of different light sources, mainly daylight and artificial light.