Ok, I'm sorry, this is a bit of topical (Starwars) click-bait, but it is at least relevant. Kinda.
One of my readers, Uday Kiran, contacted me asking me for tips on shooting very dark or black subjects (Sloth bears, Drongo's etc...), as often they are not very well focused.
Well, this is a common problem when photographing very dark subjects, and like all problems to find a solution, you need to understand the why it is occurring!
The Problem
Digital camera auto-focus systems mostly work in two ways, contrast and phase detection (there are other methods like dual-pixel). In order to understand how the problem arises, we must first understand how the camera tries to focus. I will give you simple idea of how they work here, but please remember it will be very simplified!
Phase detection:
Ok, the best way to envisage this is like this, imagine your camera sees two images of your subject. When the subject is in focus, the two images will overlap perfectly, but if they do not, then they are out of focus. So your camera will quickly check if the two images overlap where your AF point is, getting the image you want!
Contrast detection:
The other main system for focusing is based on contrast. The basic premise is that there will be the most contrast in an image that is in focus. So you AF point will take little histogram readings looking for the focal position that gives the most contrast at that AF point.
Now, both these systems work very well on the assumption that there is:
- A clear and determinable subject in the AF point
- There are areas of texture and contrast for the systems to use as a reference
BUT, if you AF point is on a big dark area, any contrast or texture is so small, it can not detect if well, and it will struggle to get the correct focus. The same thing happens when shooting in low light situations (I will make another post about this another day).
The Workaround
Now we know WHY focus is difficult in these situations, how can we get around it? Here are my tips! If you have any more, please leave a comment at the end of the post. :)
Focus on the best area!
Your auto focus needs contrast or outlines to focus currently. Any pure dark subject is difficult for your AF system, so try and focus on any part of the subject that has texture or contrast. THE EYE should always be your primary focal place.
Use the center AF point!
Not all AF points are equal, your center point is always the best and most sensitive one, so I suggest using that to focus, and then recompose to get the composition of choice.
Increase the depth of field!
Use a narrower aperture (higher f/ number), this will give you a deeper depth of field and means more of your subject will be in focus, and increases the chance of getting better focus. By doing this, you will need to compensate with reducing your shutter speed or increasing your ISO. This is always a balancing act, and must be adjusted on a case-by-case basis!
I focused on the stick to get the best focus of the Drongo!
Focus on the feet!
If the you can't focus on subject, focus on something else in the focal plane, like the ground or branch it is standing on. Combining this with a narrower aperture can you can get some good results.
Manual focus!
It's old school, but if all else fails, screw it and give it a shot! :)
Keep clicking!
Use continuous shooting mode and keep clicking. If the first or second images are out of focus, the later ones might not be... Play the statistics game and shoot more than enough, it will increase your odds of getting a good one. This is one of the major advantages of digital, so use it! :)
I watched where the elephant was walking and got in position for when it crossed a beam of sunlight!
Get better light!
The more light, the more your AF system has to play with. Now, for wildlife, this is PURE luck and mostly out of our control. But if your subject is moving, see if they are moving towards better light and get into position for that. Pre-visualization!
DO NOT use focus assist beams (from speedlites or otherwise) when photographing wildlife, it can be very disturbing for them. Remember you are in their home!
Metering (an added bonus)
Also, please remember to correct your metering to compensate for photographing a dark subject. Your cameras metering system will see a big dark patch (your subject) in the image and will try to correct for it by increasing the overall exposure! So, you will need to slightly under-exposure your image to compensate for this.
I hope you find this useful Uday, and if you, or anyone else have any other questions, leave a comment below, or contact me. I'll do my best to answer it! :)
Remember, a click a day, keeps the psychiatrist away! :)