Airliners.net

Hi all,

I was at Farnborough airshow today (my first airshow as a 'spotter' with my new camera! a canon S5 IS). It was a pretty dull day for most of it though it did brighten up after the Vulcan strutted her stuff!

Anyway when photographing propeller aircraft and helictopters I switched my camera to Shutter Priority so that I might be able to use a slightly longer exposure to get some blur on the props to give a sense of speed/rotation (I had been shooting on Aperture Priority with the aperture at 7.1/8.0). When I focused the shot (half-press auto focus) the aperture setting came up as red (at 8.0), which on my camera means that the required aperture setting and implied the aperture needed to be more than 8.0. I tried taking a shot anyway to see how it would come out and it was very overexposed.

Could anybody please tell me the 'physics' behind this and why it happened, and what I can do in the future to get the effect I wanted?

Many thanks in advance,

Dan

Well from the sounds of it, your lens reached the minimum aperature (f 16 or 22) and as it couldn't stop down any further, the only option would be to raise the shutter speed. One other compensation you could have made in this situation would have been to Lower the ISO speed which reduces the chip amplification and that should have helped.

You can always use a ND filter if you need to slow down some and your camera won't let you.

Hello Dan,

the exposure of an image mainly depends on three factors:

1) The aperture
2) The exposure time
3) The photosensitivity (nowadays you can choose and change the ISO settings very quickly, back in the non-digital age you had to choose prior to shooting   )

I don't know how much knowledge of a lens you have (as you have a PS camera..) but every lens can change "the hole" through which the light comes to the sensor.

high number -> small hole -> "less light" -> longer exposure time but also more depth of field
low number -> bigger hike -> "more light" -> shorter exposure time but less depth of field

So there are different settings to get the exposure right but with different effects  
To second Stephen, in your case the aperture needed to properly expose the picture was out of the available range and therefor the pictures got Overexposed.

One more word to the photosensitivity the higher the ISO settings you choose, the shorter you can go with the exposure time by a fix aperture. But be careful, you get less detail and the grain increases rapidly. So try to always shoot the slowest ISO possible for the conditions!   

Hope this helps a bit, and if you have any further questions, just ask!  

Bjoern

Quoting KLM772ER (Reply 3): the exposure of an image mainly depends on three factors: 1) The aperture 2) The exposure time 3) The photosensitivity

Quoting KLM772ER (Reply 3): high number -> small hole -> "less light" -> longer exposure time but also more depth of field low number -> bigger hike -> "more light" -> shorter exposure time but less depth of field

Quoting KLM772ER (Reply 3): So there are different settings to get the exposure right but with different effects

This is 90% of what you have to know to master the art of photography  

Quoting JeffM (Reply 2): You can always use a ND filter if you need to slow down some and your camera won't let you.

   I do not know if you can use filters in your camera, though.

j

Thankyou all for your help. I was shooting at ISO 80 the whole day so it seems my camera simply wasn't able to do what I had in mind in this case. Seems as though I might be migrating to full DSLR a little sooner than I'd expected!

Dan

Keep in mind, exposures at the same ISO, aperture, shutter are going to be the same, regardless of SLR or point and shoot. The SLR might allow you to add a lens with a smaller minimum aperture or more easily screw on a neutral density filter, and of course there are other advantages, but it won't fundamentally change the picture-taking process.

I wish mine went down to ISO 80. For some reason Nikon decided that because noise was almost invisible at ISO 200, that's what the minimum ISO should be on the D40.