Av / Tv or full manual shooting modes?

Which shooting mode to choose? You have no idea how many times I hear the question! Many professionals think that because they are pros, they should only shoot in full manual mode… There is absolutely nothing wrong with shooting in Av or Tv mode when you know why you should do so. I personally shoot in full manual about 90% of the time, and the rest is split between Av (Aperture priority) or Tv (Shutter priority) modes. Let me lay down my reasoning behind choosing the proper mode…

There are two main factors: background and light source.

changing backgound              constant background

constant lighting                         manual                             manual or Av / Tv

changing lighting               manual or Av / Tv                            Av / Tv

The table above is what I believe is proper to do and here is why:

1. Constant lighting & changing background

A perfect example of that situation is when creating photographs of birds in flight.

Harris Hawk in flight
ISO 1600 | f/6.3 | 1/4000 sec. | Manual mode | AI servo | rear focusing
This photograph was created with the Canon 600mm f/4 L IS II USM lens (Canon 600mm f/4 L IS II USM review) and the Canon EOS 5D mark III on tripod with a Jobu Design Gimbal Head.

Birds in flight will move from one background to the other, from blue sky to tree line, to ocean waves and so on. The issue with using the semi-automatic modes (Av, Tv), is that they are designed to blend all tones into an ideally exposed grey tone. That means that if your subject is white and your background is very dark, you will need to dial some negative exposure compensation in order to properly expose your photograph. Otherwise your white subject will end up being overexposed and the whites will be clipped in your histogram, leading to a non recoverable loss of information. So, your camera is constantly assessing the ideally exposed grey based on where you are pointing at, hence constantly re-assessing your bird during its flight. Of course, you are not likely to have time to adjust the exposure compensation between flying from the blue sky to the dark mangrove! So, it is very important to stick to fully manual mode, where your subject is going to be well exposed no matter what the background is.

2. Constant lighting & constant background

You may use any semi-automatic or fully manual mode without consequences in this scenario. My preference will go to fully manual though.

3. Changing lighting & changing background

Those are the most difficult situations. Let’s imagine a bird in flight close to the tree line, with the sun playing hide and seek with the clouds. I would lean towards fully manual with constant check of my histogram and adjustments of my shutter speed.

4. Changing lighting & constant background

If the lighting conditions are constantly changing, but the background is pretty much the same, I will opt for Av mode with a good judgement on which exposure compensation to dial in.

Waved Albatross – Espanola Island, Galapagos Islands
ISO 640 | f/5.6 | 1/8000 sec. | Manual mode | AI servo | rear focusing
This photograph was created with the Canon 600mm f/4 L IS II USM lens (Canon 600mm f/4 L IS II USM review) and the Canon EOS 5D mark III hand held.

We had a constantly changing weather that morning on Espanola Island and I was focusing on this Albatross with the green grass as background. Instead of having to adjust the shutter speed back and forth as the sun came in and out, I opted for shooting in Av mode and dialing -1 in exposure compensation as my subject was lighter in tones than the background. Another good example would be to shoot in a rainforest, where the sun might be one second going through the foliage, and the other being blocked by a tree. Photography in those conditions will require the use of Av mode a lot more.

When do I use shutter priority or Tv mode?

Controlling the shutter speed is extremely useful when creating pleasing blurs!

Waved Albatross – Espanola Island, Galapagos Islands
ISO 100 | f/8 | 1/15 sec. | Tv mode | AI servo | rear focusing
This photograph was created with the Canon 600mm f/4 L IS II USM lens (Canon 600mm f/4 L IS II USM review) and the Canon EOS 5D mark III hand held.

I typically set my shutter speed between 1/15 and 1/30 of a second when creating blurs.

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Steven