Night Photography - iPhone

 Experiments in Manual Settings on the iPhone Camera

Introduction

While looking into the iPhone camera manual settings I found there is an adjustment setting for nighttime photography

References

The Apple iPhone User Guide includes a Guide on Taking Night Mode photos but does not explain what is happening and what changes to expect.

I found a better article online on the MacRumors site.

Introduction

In normal use the exposure setting on the iPhone camera is set automatically, presumably to keep it as short as possible within an acceptable ISO range.  If the camera detects the image is a night scene it automatically switches to automatic night mode.  The camera analyses the scene and computes how many images need to be taken for an optimised output.  The camera sets a total picture time taking into account how dark the scene is and how steady the camera is.  This time setting is different from the exposure time setting as the camera will take multiple photos within the time allocated to it.  

The setting can be set at off, auto, or maximum.  

Remembering back to our discussions on the exposure triangle, I decided to experiment and see how this nighttime control affects the aperture and ISO values.  The following 3 images were taken on each of the 3 available nighttime settings.

Off 1/17 sec (-2 stops) f1.5 ISO 4000 (+2 stops) 5.7mm	Auto 1/5 sec f1.5 ISO 1000 5.7mm	Max (1sec) 1/4 sec (+1/3 stop f1.5 ISO 800 (-1/3 stop) 5.7mm

The camera uses image stabilisation to allow longer exposure periods, more images; a crosshair appears in the image to help the user to keep it steady.

There is a slight lightening in the sky in the images on the right but other than that I can see little difference in the photographs.  There is no visible increase in grain resulting from the change in ISO.

Not surprisingly, there is no difference in depth of field (as the lens aperture is constant)

Comment

Moving the nighttime slider is doing something other than just changing the exposure setting and ISO.  The images should not vary as the same EV has been used on each 

The camera is taking multiple images and then stacking them together in order to select the best bits of each. This enables it to set different exposure levels for different parts of the image and to cope with a high dynamic range.

Conclusion

I have identified little creative control affecting the image in this setting, the camera makes all the decisions.    The camera is taking multiple images each time before combining them and selecting the best part of each.  This is similar to the exposure bracketing and High Dynamic Range processing I sometimes do using my DSLR.  The difference is the iPhone is doing it all with no human intervention, my camera needs manual editing in third party software, more work but I am in control.  

I have not yet seen any strong enough results to justify use of this setting given that I can edit images in LightRoom or Photoshop (especially if I take RAW files on my iPhone).