Slow shutter speeds and overexposures

Poolkas

I headed out this evening at 7 pm with my D3100 in lovely evening sunshine (odd for Northern Ireland) to try out some shutter priority shots at the local salmon weir. I found a tree reflecting on a pool above the weir with lovely blue sky behind.

I used my 50mm f/1.8 AF-S. Tried Auto to get indicative readings before going to manual. Selected 2 seconds and highest f-number (f/22) at an ISO of 100. Guess what? Everything was blown out.

If I used a shutter speed below 2 seconds, the water would not blur so it had to stay. Could not reduce ISO. Camera would not give me more than f/22, though fleetingly I saw f/35 which disappeared almost instantly.

Changing to my 18-55mm f/4-5.6 kit lens I saw a little improvement, but the sky was so pale. Trees and background greenery were washed out. I don't yet know enough to get into filters, nor do I know enough about Adobe (I have NX View2 and Gimp).

What am I doing wrong? Do I need filters and if so which? Thanks, Mícheál

sunchaser

Hey @Poolkas (Micheal) - I'm thinking a polarising filter may of helped with the colours, but not sure about the blown out images. Maybe someone else can shed some light on it! - Matt

caflagg

Oh my! I'm having the same problem, with the same lens (the 50mm f/1.8). Admittedly, I know almost nothing, but it sure is frustrating. I was able to reduce the ISO, but as soon as I turned off the camera it reset itself and all images were once again overexposed.

Moose

Howdy @Poolkas - Here's the dealio...if you want to use slow shutter speeds to capture movement (flowing water) in bright daylight, you'll need the assistance of a Neutral Density filter. ND filters reduce the amount of light entering through the lens.

Choosing the right ND for your needs really depends on the effect you're going for and the amount of light available in the locations you normally shoot at. For example, if you're in a forest with tall trees and want to capture flowing water a 0.9 ND filter would be sufficient. However, if you're at the beach and you'd like to smooth out the ocean, you'll need a really dark 2.7 ND filter.

These numbers (0.3, 0.6, 0.9, etc...) refer to the darkness level of the filter. The larger the number, the darker the filter.

Based on your current setup, I would purchase a Hoya 58mm ND 0.9 filter (see here) and a 58mm-52mm step down ring (see here). This will allow you to use a single ND filter on both of your lenses, without having to spend the money on two filters.

Hope that all makes sense. Happy shooting! :)

Poolkas

Well I have now got a ND4 filter but haven't used it yet. I have in the meantime discovered blinkies! The shots I was trying to get were pretty impossible. I have also discovered the HISTOGRAM! If you use the histogram which is really a graph showing the amounts of light, from 0 to I think 265 this will show what you might expect in terms of over or under exposure. Anything piled up to the left is dark, to the right is bright. If you have a bright scene say on a sunny day (eg bride's dress) and a dark mass eg large tree trunk in shade, you will have a high pile on both sides. Cameras don't handle this well. In my photo I had a bright background (sky) and dark water. The fact that I was slowing the shutter to get a milky effect on the water meant the sensor was getting the time to pull in too much light from the sky. Result, blown sky. Solution, I hope, ND filter. Or multiple exposures and a pile of Photoshopping!
Thanks for your help.