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I have watched a few YouTube videos now and one guy states that you should have a smaller aperture but to compensate for the lack of light coming through, you should set the shutter speed higher, something like 15 seconds so that MORE light comes through for improved dynamic range.

But another You-tuber states that you should set the aperture to max so that the most amount of light comes in BUT set the shutter speed to 0.5 / 1 or 2 seconds.

Who do I believe, which is better and why?

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3  
It all depends on the subject matter and how you want the image to look. Both approaches have their uses. –  Michael Clark Feb 1 at 23:38

3 Answers 3

Both you-tube answers are correct. Each has its trade-offs and produce different image effects that are a matter of 'artistic' choice or are more appropriate for the type of subject being photographed:

1: long shutter exposure, small aperture

  • Deep depth of field due to small apeture (nearly everrything in the image will be in-focus) (may be desirable or undesirable effect)

  • Motion-blur if subject is in motion due to long shutter exposure (may be desirable or undesirable effect)

  • Risk of camera-shake blur if camera is hand-held due to long shutter exposure (usually undesirable effect)

2: shorter shutter exposure, larger aperture

  • Shallow depth of field due to larger aperture (subject is in-focus, background is more out-of-focus) (may be desirable or undesirable effect)

  • Less or no motion-blur if subject is in motion due to shorter shutter exposure (may be desirable or undesirable effect)

  • Less risk of camera-shake blur if camera is hand-held due to shorter shutter exposure (usually desirable effect)

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This depends on a few things. Faster shutter speeds are required if there's movement in your shots unless you want to average them out of the shot, in which case you want a longer shutter speed so that they don't show up. Aperture also determines depth of field, which may or may not be important for you. Also consider if you have the sky in the shot star trails can appear after only a few seconds, depending on your focal length. Skies look good with either no star trails or long star trails, but short star trails tend to look sloppy.

The best thing you could do is try out both and see which gives you the results you're after. These things tend to be more guidelines and starting points than strict rules.

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I think you're confusing "smaller aperture" with "smaller F number". The F number is a quotient (something you divide into), which is why it's expressed as f/# (# being a number), eg.: f/4. Hence, the size of the aperture is the inverse of the number expressed:

  • higher numbers are smaller apertures
  • smaller numbers are bigger apertures

Whatever the case, there are no "right" settings here, especially since you've provided no details about your subject matter; it's all dependent on the results you're looking to achieve.

In low light, you'll generally want a wide aperture (big aperture, small number) no matter what you're shooting, unless your subject is consistently lit and non-moving for the duration of the exposure (and you have a reason for using a small aperture, such as a deep DOF or sharper image, depending on your lens)

For example, shooting landscapes with a starry sky where you want no movement in the stars (eg.: milky way shots) you want the widest aperture possible and a fairly high ISO to enable a relatively short shutter (definitely no longer than 30 seconds). Anything else will start to show streaks.

For star trails, you'll still want a wide aperture (otherwise, the relatively dim points and moving of light will not reach the sensor), but you can lower your ISO because you'll be using a shutter of 30 minutes or longer. There's also a point to be made here about exposure stacking, but that's tangential to this discussion.

Determining the correct exposure for any picture is a matter of balancing the "triangle of of exposure" -- shutter, aperture and ISO -- based on what the meter is telling you and how the secondary effects of each exposure factor will affect the result.

There are ton of resources out there for learning exposure and all of them a Google search away.

But I'll leave you with a simple chart:

             LOWER NUMBER                     HIGHER NUMBER
          +----------------------------------------------------------------+
  SHUTTER | bright exposure, blur motion  |  dark exposure, freeze motion  |
SHUTTER " | dark exposure, freeze motion  |  bright exposure, blur motion  |
 APERTURE | bright exposure, shallow DOF  |  dark exposure, deep DOF       |
      ISO | dark exposure, less grain     |  bright exposure, more grain   |
          +----------------------------------------------------------------+

" means seconds. When the shutter displays as 2", it means 2 seconds. It might be easier to ignore the second line of this chart and consider the seconds as negative numbers. So, anytime the camera shows " by the number, reverse the SHUTTER rule.

You can begin to see how the factors of exposure interact with each other.

There are triatary effects and other tangential factors to consider as well, but those are beyond the basics.

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How does that chart work for shutter speed? If I start from 1 second, does "higher number" mean 5 seconds, or 1/500 seconds? What if 5 seconds is not enough? Does a "higher number" like 25 seconds freeze motion better? –  Esa Paulasto Feb 2 at 4:22
    
@RecoveringNerdaholic I think the original question understands a smaller aperture with a larger f-number is narrower and lets in less light. I think you misunderstand that his use of higher shutter speed means longer shutter speed. 30 seconds is higher than 1 or 2 seconds in the question. –  Michael Clark Feb 2 at 12:26
    
@Michael Clark I understand that too, but whenever someone talks about "smaller aperture" i never know for sure if they meant "smaller number value -> wider opening for the light" or "narrower opening for the light -> bigger number value". –  LeFauve Feb 2 at 23:42
    
Since the original question also includes "...to compensate for the lack of light coming through..." I think it is fairly clear what was meant in this case. –  Michael Clark Feb 3 at 9:40
    
@EsaPaulasto, sorry, you're right, I should clarify this. Most cameras will display just a number for fractions of a second for a shutter speed, so: 500 > 125 and will freeze motion better. 500 appears as a higher number, but it's actually smaller because it's a fraction. Indeed, the rule is reversed when exposures shutters are >= 1 second and no longer fractions. –  Recovering Nerdaholic Feb 3 at 15:11

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