using lens in low light

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    • #89251

      last night I had used a 35mm lens on a canon 70d to shoot a program at my church. the image was a little noisy. Also the sound did not come out that great. My question is what is the best lens to use with a canon 70d during low light please. I am a beginner and I want to get better !!

    • #213591
      Pete Tomkies

      The focal length of the lens won’t affect how noisy the image is, that’s related to the exposure settings you are using. For low light filming you want a lens with a large aperture but be aware that the wider the aperture the shallower the depth of field will be so focusing will be more difficult. Also the ISO setting will affect the noise in your image – for video you should keep to ISO 800 or below. The built in microphones on DSLR cameras are not good and the built in pre-amps often add hiss to the audio. Ideally you should record the audio using a separate audio recorder and microphone(s). If you do need to record audio in camera look to get something like the Rode Video Mic Pro which has a +20dB setting to avoid excess audio hiss when recording with DSLRs.

    • #213601

      First of all – use manual settings! If you turn your camera to the green spot on the wheel, none of this advice will help.

      That said, there are a millions articles online explaining how cameras work and I would suggest you read up on something called the “Exposure Triangle.” But in a nutshell – the exposure is affected by three factors:
      1. How much light is hitting your sensor (aperture measured in f-stop)
      2. How long that light hits your sensor (shutter speed)
      3. How sensitive your sensor is (ISO)

      Without know the settings you used, it’s hard to say where things got noisy. But the simple fact is this – cameras need light to work and the less of it you have, the harder it is to get a clean image.

      So here are my suggestions for low light situations –

      Like Pete said, you may want to consider a new lens with a lower f-stop (lower number equals more light – I know, it’s counter-intuitive.) An f/2.8 will let in twice as much light as an f/4 and 4 times as much as f/5.6 since each full f-stop lets in twice as much light (1X2X2=4.) Most budget zoom lenses have a variable aperture so the more you zoom in the less light in lets through. I.e. the Canon 18-135 STM is an f/3.5-5.6. I own this lens and generally quite like its quality and versatility for the price. However, it is not considered a “fast” lens due to the poor f-stop on the zoom end.

      Lets assume you can’t afford a professional fast zoom with a constant f/2.8 aperture throughout the zoom range. You might consider a zoom with a constant f/4, but even those will set you back a fair amount. With Canon L lenses, you are getting great lenses but at a premium cost.

      Since you have an APS-C sensor, you might consider the more affordable Canon EF-S 17-55mm f/2.8. It works quite well in low light and has image stabilization which I always recommend for video work. It doesn’t have a massive zoom range, but it will give you much better low light ability than your typical f/3.5-5.6 zoom.

      If that is outside of your budget but you must have faster glass, consider a variety of prime lenses.

      The EF-S 24mm STM is an f/2.8 lens designed specifically for APS-C cameras. It will give you a noticeable increase in your field of view.

      The EF 40mm STM is also a 2.8 lens. Both of these lack IS (image stabilization) but at $150-ish they will give you a lot of low light bang for your buck.

      But like Pete said, the lower the f/stop, the shallower your depth of field. Plus, the 70D doesn’t do quite as well in the auto-focus department at 2.8 or below.

      So what else can you do? Lower your shutter speed. If you halve your shutter speed, you double the amount of light let in. This halving or doubling is equal to one stop of light.

      A good rule of thumb is to have a shutter speed with is twice your frame rate (or close to it.) This is what filmmakers typically use. You could even go as long as your frame rate but the slower the shutter speed, the more motion blur you get. For example, 24fps uses 1/50, or 30fps uses either 1/60 or 1/50 depending on your camera.

      The third part of the exposure triangle is ISO. 400 is twice as sensitive as 200 (one stop difference.) 200 is twice as sensitive as 100 (again, another stop of difference.) This numbering system is a bit more intuitive since 400 is 4 times more sensitive than 100.

      It has been said that Canon chips like certain ISOs better than others. I’m not sure if this is true or not so take it with a grain of salt. For good measure, I typically use multiples of 160 (i.e. 320, 640.) The lower the number the more light you need, but the cleaner the image.

      If you’ve maxed out your lens’ f-stop, and dropped the shutter speed as low as you feel comfortable, then you must raise the ISO to get proper exposure. Pete said 800 or below, but you might be surprised with how high you can go with the 70D. 1250 isn’t bad. 1600 and even 3200 could do in a pinch. Experiment a bit and see for yourself what is acceptable and what isn’t.

      But let’s say you’ve done all these things and you still need to improve your image. Here are two other thoughts:
      1. Don’t be afraid to underexpose by a stop or two. Stage programs with bright lights often give hot spots that are difficult for your camera to account for. The metering will tell you the exposure is too low, but if you check your histogram you may find that there is a huge spike on the far right side. This means those highlights are getting blown out. Faces loose detail first in these situations. A little extra darkness is better than blown highlights.
      2. Use a flat picture profile. You can use a neutral setting provided in the camera or add a custom profile such as Cinestyle and use your editing software to adjust the final image. Flatter profiles help preserve details in both the shadows and highlights of your images while minimizing digital noise.

    • #213726

      Thank you Joesph and Peter for your great advice

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