How to reduce ISO in low light with slow zoom lens?

Question

I have a Nikon D5600, and my usual lenses are the 35mm prime lens and the Nikon 16-85 zoom. I like the zoom a lot for carrying around outside. But when we were in Spain, I was continually confronted with the problem that it is an f/3.5 maximum aperture lens (and smaller at longer focal lengths), which really doesn't work well inside; I didn't have a tripod with me and in any case they generally aren't allowed inside.

The 35mm prime lens, which is f/1.8, is mostly fine, but it is a net 52mm or so with the DX mount, so I often can't use it to get the shot I want.

The end result is that I have (with a 1/125 minimum shutter speed) lots of shots with ISOs higher than I'd like. The image quality is not terrible at those ISOs, but I'd love to have another solution. There don't appear to be any decent other solutions. Any suggestions?

Answer 1

With any gear: The rule of thumb for getting photos without noticeable camera shake is:

shutter_speed[s]  ≤  1[s] / (focal_length[mm] * crop_factor)

Note that if you like pixel peeping, it will probably need much shorter shutter speeds (at least 2 thirds of a stop). E.g. for your 35mm lens, you should be good with something faster than 1/60s.

Also note that - as @rackandboneman commented - point light sources might require faster shutter times because you will see camera movement in them quite easily.

Lenses (or bodies) with image stabilisation might help with camera shake - they will not, however, help you if you have to deal with subject movement.

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As to gear:

• Tripods (not allowed in a lot of spaces, somewhat bulky to carry) or monopods (offers far less stabilisation) might help because they limit camera movement.
• Speedlights can help, but are prohibited in some places (museums, churches,...). They will also change the light distribution in your scene.
• Faster lenses will allow for less ISO and/or faster shutter speeds - you trade in depth of field, though. Also, fast lenses are typically more expensive and heavier than your average kit lens.
• A full frame sensor will usually provide better image quality in high ISOs.

Will you need any of them? That depends. It is important to have realistic expectations so to avoid GAS. I will give an example:

This is a 200% crop from a picture I made inside a church. The floor is slightly underexposed because I wanted to properly expose the ceiling. It was made with a 24-105mm f/4 lens with image stabilistaion on a full frame camera. The actual parameters are: 24mm | 1/30s | f/5.6 | ISO 3200. The picture is unaltered (i.e. absolutely no de-noising, not exposure-compensated).

Is this bad? No, not really - with a bit of de-noising, it looks fairly good, and for A4-sized prints, I would not even need to do that.

Answer 2

Some options to consider:

• Meditate on what it means for ISO to be high.

• Use the 35/1.8. You can't get the shot you want with it, but you might still not get the shot you want with the zoom lens.

• Use slower shutter speeds. 1/125 may be faster than necessary. Since you state you are using the zoom lens for focal lengths wider than 35mm, 1/60 should be fine. Even slower if your lens has image stabilization. I use 1/40 throughout the zoom range of my kit lens (18-55). I use 1/100 for non-stabilized lenses (up to 135mm).

• Use a flash (with diffuser or bounce), or find some other way to add light.

• Post process to remove noise or convert to black and white.

• Put the camera down and just enjoy the moment.

• Get new lenses. Here are some that might work:

  • 24mm or 28mm prime (any make)
  • 24-70/2.8 or similar (any make)
  • Sigma 24-35/2 Art

  • Sigma 18-35/1.8 Art

  • Slower constant aperture (F3.5, F4) lenses may be helpful if you find yourself drawn to the long end.

  • Faster variable aperture lenses are available (F2.8-4), but image quality at F2.8 isn't great on the ones I've tried.

• Try a focal reducer? Too bad... They don't work on DSLRs.

• Get a new camera that produces less (objectionable) noise at high ISOs.

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The end result is that I have... lots of shots with ISOs higher than I'd like. The image quality is not terrible at those ISOs, but...

It's not clear to me whether you want lower ISO values for the sake of having lower ISO values or whether you actually find the noise that results from high ISOs objectionable.

For instance, I don't like chroma noise, such as may be seen in flolilo's sample image. But I don't mind more monochromatic noise, which my camera tends to produce. So even though I'd like lower ISO values, I let my camera run up to ISO 12800 because I know I'd miss the shot otherwise. However, if I do need cleaner images, I find ways to add more light.

Here's an image taken with a Sigma 18-200/3.5-6.3 at 69mm F4, 1/125 sec, ISO 8000. You can view it at 100% to see what noise from my camera looks like. (No colored specks.)

Here's an image taken with a Canon FD 35-105/3.5 at 105mm F3.5, 1/75 sec, ISO 12800. There is a near absence of green light, which means the sensor was working at only about 45% capacity. (Non-standard color matrix with green sensels covering about 55% of the sensor.) I converted to black and white because I couldn't make color work without the green channel.

Answer 3

If you want a faster wide angle lens you could look at the Tokina AT-X 14-20/2,0 Pro DX. This is an expensive lens thou.