EOS 90D Trouble focusing in low light

[moe313]

Hi everyone,

I am  new here on the Canon Forum and just wanted to say hello.My name is Moe and I recently got into photography more seriously. I have  always admired Canons gear so I finally picked up a Canon EOS 90D and I am really enjoying it so far.

That said, I have  run into a bit of an issue and was hoping someone here could help. The autofocus on my camera seems to struggle in low light especially when using certain lenses. It hunts a lot before locking in and sometimes it does not focus at all. I am not sure if it is  a setting I need to adjust or something I am overlooking.

If anyone has experienced something similar or has tips on how to improve autofocus performance, I do really appreciate the help. Also happy to be part of this community and learn from everyone here.

Thanks in advance,

[kvbarkley]

How low?

Autofocus can't work miracles.

What lens?

[stevet1]

Moe,

All cameras struggle in low light, so the situation is not unique to the 90D.

There is really one solution, and that is to add more light.

That being said, there are a couple of things you can do to tweak the situation and help your camera out a little.

One way is to widen your aperture to let more light in. You didn't say what lens you are using, but an aperture of f/2.8 will let in more light than aperture of f/11. 

Apertures are a function of the lens and not of the camera.

Apertures also controls your depth of field, so if your subject is close to you, and you use a real wide aperture, your subject will be in focus, but your background will be blurry.

You didn't say what you are try8ng to take a picture of, and under what conditions.

Is it indoors, or outdoors?

If it's indoors, you can turn on some lights. If it's outdoors, some people will shine a flashlight on what they are trying to take a picture of.

Another thing you can do is if you can find a line in your scene that has a lot of contrast between the dark and the light that is the same distance as between you and your subject, try to focus on that spot of greatest contrast.

In the meantime, try to read up and study the exposure triangle and how the three legs of that triangle (aperture, shutter speed, and ISO) work together.

Steve Thomas

[zakslm]

moe313,

Steve and kvbarkley gave you good advice.  

I'd like to expand a little on that advice and tell you what (sometimes) works for me.  In low light situations where my camera (a 90D and before it a Rebel T7) struggled to focus in low light, I found it works best to use the camera like I used my autofocus film camera years ago which is to use the center focus point to obtain focus on the subject or object I want in focus, lock focus on it then recompose and then take the shot. 

As the chart that kvbarkely inserted in his reply indicates, the center AF focusing point is the most sensitve of the 45 focusing points of the 90D.  On page 2 of the EOS 90D Supplemental Information booklet has thefollowing diagram that further expands on his points: 

To follow the steps I outline set up your 90D as follows:

Focus Mode/Operation:  One-Shot AF

AF area selection Mode:  Single-point AF

Focus Point Selection:  Mmanual selection of the CENTER focus point

Taking the picture:  Put the center focus point on the subject or object you want in focus and (if your camera is set up where depressing the shutter button half way focuses) press the shutter button down half way until the camera beeps to indicate that it has focused.  Keep pressure on the shutter button and recompose the shot and then press the shutter button down the rest of the way to take the shot.  If you've separated the focusing function so that the shutter button does not actuate focus but uses the the "AF-ON" (back button focus) to start and hold focus, then instead of holding the shutter button down half way until you hear a beep, hold the AF-ON button down until you hear the beep, then recompose and depress the shutter button to take the shot.

Another trick is to use a penlight flashlight or small LED flashlight to illuminate the subject or object you want in focus, lock focus, turn off the flashlight, recompose if necessary and take the shot.  This technique may require a "third hand", but it works!

As with most things, it will take practice and a period of trial and error until you find what works best for you.  But as Steve recommends, try to read up and study the exposure triangle and how the three legs of that triangle (aperture, shutter speed, and ISO) work together.  Also go through the manual and the supplemental information on the 90D to get familiar with the 90D and it's capabilities.

Good luck,

LZ

[deebatman316]

The camera focuses wide open regardless of the aperture set. It will stop down before the exposure is made. Also to the OP you can use the built in flash to provide an AF Assist Beam. This will be very audible most users here call it “disco flash”. An external speedlite such as my 600EX II-RT can project a red grid pattern. To assist the camera in low light for AF. This is called an “IR/ Infrared AF Assist Beam” though this beam is visible red light and NOT IR. If it was IR we couldn’t see it. Mirrorless Cameras cannot utilize this older type of AF Assist Beam. Instead the speedlite will use the same method as the built in flash to provide an AF Assist Beam. Mirrorless Cameras cannot detect the color red very well.

[wq9nsc]

OP, you have received good advice and I would add to LZ's excellent post to be sure and put the center point on part of the image that has good contrast/detail or it will struggle to focus.

Rodger

[moe313]

Thanks so much everyone.I really appreciate the warm welcome and all the detailed advice this is exactly why I joined the Canon forum. You have  all given me a lot to think about and try out.

To answer a couple of the questions: the issue mostly happens indoors in dim lighting like living rooms at night. I have  noticed it more when using my EF-S 18–135mm lens though it seems better when I use my 50mm f/1.8. Makes sense now given what many of you said about aperture and available light.

Using the center af point with single point AF and One-Shot mode sounds like a great place to start I will definitely try that technique with the focus-recompose method. I had not considered using a small flashlight to help lock focus either but that sounds super handy even if it is  a bit of a juggling act. The disco flash made me laugh, but I’ll give that assist beam a shot too.

I am also going to go back through the manual and the supplemental info booklet, as suggested. I have  read about the exposure triangle before but clearly I need to spend more time really understanding how it all works in practice.

Thanks again for all the advice and the encouragement it is great to be part of such a helpful and knowledgeable community. Looking forward to learning more and sharing my progress.

Cheers,
Moe

[stevet1]

Moe,

May you have many happy shooting experiences.

Steve Thomas

[MrWalleye73]

Yeah, I've learned that the single point/Center point AF really helps in low light (same camera too). 90D is my first digital camera and it's been very good so far and fun! Enjoy!