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I wanted to practice photography with flash so turned off the room lights and tried to take a photo but there is a circle that shows in viewfinder when the camera has locked the focus on something, well I couldn't get that circle to show, meaning it wasn't able to focus. So as much as I press the shutter button it resists and doesn't allow me to take a picture. However I remembered that I could have turned on the focus illumination light to help it focus maybe that was my mistake but other than than is there other things I should know about?

Here is what I was trying: I was in Aperture mode, with f 1.8 and ISO 800. Camera was Nikon D-810 which they say is great for focusing at dark. The flash wasn't the camera flash, I has just bought a bigger flash that sits on top of camera, one of those.

So in these situation should I for example switch to manual mode?

  • In the last sentance of the body of your question, do you mean manual focus mode or manual exposure mode? – Michael C Feb 14 '15 at 0:20
  • @MichaelClark Manual mode of camera – Brandon Feb 14 '15 at 18:56
  • Manual focus mode or Manual exposure mode? They are two different things on your camera. – Michael C Feb 15 '15 at 7:38
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When they say the AF system does well in the dark, that doesn't mean when it's pitch black. All AF systems have lower limits, and on your D810 that value is -2 EV at ISO 100. Even if you're focusing manually, the same parts of the AF system get used to detect whether or not you're focused.

You have a few choices, most of which involve more light:

  • Focus manually in the dark and squint a lot
  • Turn on the lights and focus manually
  • Use AF with the lights on and lock it in before turning the lights off
  • Enable the AF assist lights on your camera and flash if they have them

If you're not using the AF assist light, the AF system will report no focus after you turn the room lights off and the shutter release will be inhibited. There's a setting that bypasses that.

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If you were getting enough light for your exposure, but weren't able to focus, then try manually focusing - usually there is a switch on the lens that will let you do this. On manual focus, your camera will take the picture right when you shoot.

Actually, you said you were using flash - so you want to find a AF-S or AF-Assist mode on your flash - this should pre-fire the flash as your camera is focusing.

With flash, you've got a fixed time, so shoot in manual, set your shutter speed to 1/125. Then you're controlling the aperture and ISO to get the image you want.

Without flash then you have to balance your settings so that you can take the image without camera shake. This won't solve the camera's ability to focus, but here's what I do:

In Aperture mode, you can open up your f-stop to it's lowest setting, and that will get you fastest speed (lowest shake). However, you'll probably get camera shake around 1/30 of a second if you're not on a tripod, so at some point you'll be bumping up your ISO. The higher your ISO the grainer and more flat your photos are, so this may not be ideal. Personally I'd use shutter priority, set my speed at 1/30 or 1/60, and go from there.

When shooting without flash, use manual in dark areas where you want things darker than what the camera expects. As in, if you want the pictures darker than what the camera is giving you, shoot manual. If you've got time to review your shots and adjust, this works great.

If you're on a tripod, then you can experiment with much slower speeds, meaning you can get lower ISO, and higher f-stop for photos which look better.

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I keep a mini maglite in my photography bag. Any torch should do unless the room is very big. Shine the torch on the subject while you're focusing. Once focus is set, switch the lens to manual focus should override its requirement to obtain focus before taking the picture, and as long as you don't change the focal length, or turn the focus ring, or the subject doesn't move, then this will be remembered. You can then turn the torch off and take your pictures.

If you're working in the dark, I assume you're using a tripod. This will make it much easier to hold the torch and control the camera at the same time. It won't be impossible if you're handholding the camera, but it can be a bit fiddly to try and juggle with both, and also if you move at all, then the focus may change. At f1.8 you don't have much depth of field as a margin of error.

Another factor to consider here is that if you are in Aperture mode, then the camera's judgement of the ambient light will be biased by the light of the torch on the subject, and also, if the flash isn't in TTL communication with the camera, then the camera's metering isn't going to be able to take the flash into consideration for when the picture is taken. With this in mind, you may be right that you might need to shoot in Manual mode

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