High ISOs in low light situations

Black tip reef shark photographed at Maui Marine Center, Hawaii.

The above photo was shot with an ISO of 12,800, a shutter speed of 1/200th of a second, and an aperture of f/4.  Although high ISOs allow you to use decent shutter speeds in low light, the cost is digital noise.  This can be somewhat mitigated using in-camera high-ISO noise reduction filters and applying noise-reducing filters in post.  Even then, there is a price to be paid.

Fine details tend to be erraticated when high ISOs are used, and noise-reduction software does little to bring it back.  What the filters do help with is the pixelated appearance and random colour noise that is associated with its application.  The end product is certainly better, but still not as good if shot under better conditions.

Is it possible to take the same photo with a lower ISO?  The answer is yes, but again at a cost.  Like Newton's third law of motion that states every action has an equal and opposite reaction, there are consequences with every alteration you make to the exposure.  Below I have listed some other choices and what the likely repercussions would be.

• Lower the ISO - An ISO of 800 would mean using a shutter speed 4 stops slower at around 1/12th of a second.  Such a value would introduce significant motion blur from the shark; vibration mitigation technology would reduce the effects from camera motion.
• Use a lower aperture - The lens I had was a 14-30 f/4 s Z lens on a full frame body.  The focal length was already at its minimum (14 mm) to produce the stunning field of view that I had.  There is a f/2.8 version of the lens, but its price is much higher and outside my budget.
• Use a less expensive low-aperture lens - I do have access to a 50 mm f/1.4 lens that lets in a lot of light.  In fact, it lets in 8 times more light at f/1.4 than it does at f/8, and that would mean shooting with a shutter speed of 1/100th of a second (ISO 800) or increasing to an ISO of 1600 to keep the 1/200th setting.  The problem is that its field of view is so narrow that the shark would not fit in the frame unless it was way off in the distance, and the degradation of the image due to distance in water would be significant.
• Use flash - In fact I tried using my flash but I got lots of issues with reflections; flash was also not permitted in a number of areas in the aquarium.  I have included one of my flash shots below, I do not care for it.

• Use a camera that produces less noise - A large sensor with a smaller pixel count produces images with less noise at higher ISO levels.  I was using my Z7ii which has a 48 mp sensor.  Full frame cameras with a lower pixel count, such as the D780 or Z6 (the iii is now out) are available but I do not own such a beast.  I opted for the 48 mp camera for shooting portraits and landscapes, it is admittedly not the best camera for what I was doing.  

In the end, I took the best photos I could with the equipment that I have.  I imagine there are better ways to get shots, but many of them would mean having different equipment and altering the lighting through soft boxes with continuous illumination.  As such, my purpose was to get a few good shots of some of the marine life I encountered, and I think I did that.

After all, it was about enjoying my day and not about commiserating over what I could have done better.

Thanks for reading.

Eric Svendsen     www.ericspix.com