My aperture won’t go any narrower than f/8.0

Question

I am using a Nikon Coolpix p900 with optical zoom lens of 24–2000. I am going to shoot fireworks so I was trying to set up before hand. My settings are on manual, ISO 200 and 1/30, but my aperture will not allow me to dial above f/8.0.

As far as I know the higher the number, the narrower the hole so I understand why it might not go wider but does anyone know why it won’t go narrower? I’m pretty sure I could go narrower at some point so I figured I must have changed some setting or something that stopped it… what should I change so it can go narrower again? I wanted it to be at f/11.

Answer 1

Because of the small sensor the pixels are very small. If you use a smaller aperture the diffraction it causes will blur the image, so Nikon decided not to allow a smaller aperture. I have a P950 and the behavior is the same. You can drop the ISO to 100 to make up for the f/8 aperture and get the exposure you are seeking.

Answer 2

@RossMillikan explains you problem.

Another solution to lengthen your exposure is to use a neutral density filter (aka ND filter) in front of the lens.

Basic ones are not too expensive (you can also purchase individually if you know exactly what you need).

Answer 3

I’m pretty sure I could go narrower at some point so I figured I must have changed some setting or something that stopped it… what should I change so it can go narrower again?

You didn't change a setting; you're mistaken. The physical limit for the aperture diaphragm is f/8. The reason for this is because there is no advantage to stopping down farther.

The pixel pitch of the P900 is 1.34um. At apertures smaller than f/2.8 diffraction is already causing reduced contrast/sharpness. At apertures of f/4 and smaller the sensor is losing resolution due to diffraction. And by f/5.6 the loss of image/sensor resolution will be apparent in an output image. At f/8 the output resolution due to diffraction is only about 2MP, which is only minimally acceptable for smaller display sizes and non-critical work (primary green centric wavelengths). If you could stop down to f/11 the output resolution would only be about 1 MP (of actual detail w/in the depth of focus).

It sounds to me like you are setting up the camera as typically suggested in an online guide... But those guides assume you are using a DSLR with APS (f/8) or FF (f/11) sensor sizes, and they completely ignore effective focal length and subject distance (although they may have assumed near infinity?).

Because your camera has such a small sensor you will be using a much shorter focal length compared to a FF DSLR; a comparable aperture to f/11 on FF for DoF would be around f/4 on your camera. Whatever FL/zoom you choose, I would suggest leaving the aperture at maximum available (lowest #), I would also suggest using a tripod and setting the ISO to 100 with the SS at max/15 sec (ISO 200 and 8 sec would be my second choice). Then use a hat or similar to block/expose the lens in order to record the fireworks during the long shutter time. The duration of the firework explosion is really the exposure time. And using this method you can stack multiple fireworks in a single frame (by covering/uncovering the lens repeatedly).

Answer 4

All lenses have a minimum (smallest, i.e. larger f-number) aperture as well as a maximum (largest, i.e. smaller f-number) one.

Lenses for interchangeable lens cameras usually have a very low minimum aperture (> 15) that usually do not limit the photographer. Compact and bridge cameras may have one around 8 or 11, but I do not really see why that would be much of a limit either; such cameras have such small sensors that at those maximum apertures you should already have a very large depth of field.