Exposure Adjustment - Do we need filters?

[Mentalblock]

A 2 part question!!

Out for the first (proper) time with the new toy this weekend, around Bedgellert. Those who know the area will know of the many waterfalls on offer, so as you guessed, it was on with the ND filter to practice the milky water waterfall shots!

When I used my bridge camera and ND filter, I never noticed the saturation of the image changing to a greyer version, but I did this time! I'm not sure if it's because of the following; any suggestions?..............
- Dodgy filter, it was a cheap one but so was the one for my bridge.
- D90 Auto WB not adjusting correctly with filter on - I did manually change the WB, which appeared to help, but still not the same as without the filter
- Me missing something on the camera!!

Part 2........
Not being happy with the greyness of the images, I took the filter off switched to manual and tried to get the shutter speed as low as possible. Then I found the exposure adjustment button and applied lots of negative to cope with the longer shutter speed. So, 2nd question, is applying negative adjustment the same as putting on a filter?

Thanks for any help/ advice.

I've also posted in the D90 Owners Thread, but I guess it's probably not just a D90 thing!

 

[HoppyUK]

A 2 part question!!

Out for the first (proper) time with the new toy this weekend, around Bedgellert. Those who know the area will know of the many waterfalls on offer, so as you guessed, it was on with the ND filter to practice the milky water waterfall shots!

When I used my bridge camera and ND filter, I never noticed the saturation of the image changing to a greyer version, but I did this time! I'm not sure if it's because of the following; any suggestions?..............
- Dodgy filter, it was a cheap one but so was the one for my bridge.
- D90 Auto WB not adjusting correctly with filter on - I did manually change the WB, which appeared to help, but still not the same as without the filter
- Me missing something on the camera!!

Did you cover the viewfinder for the exposure? Just a guess, need to see the pic, but if you don't do that with a DSLR, you can get fogging with a dark ND filter. What filter was it? Exposure time?

Part 2........
Not being happy with the greyness of the images, I took the filter off switched to manual and tried to get the shutter speed as low as possible. Then I found the exposure adjustment button and applied lots of negative to cope with the longer shutter speed. So, 2nd question, is applying negative adjustment the same as putting on a filter?

Thanks for any help/ advice.

No. You need a filter to reduce the light - so that you need a long shutter speed - then you balance the exposure to it. You can't do one without the other.

 

[AJQS]

Was it just a cloudy day or in the shade? You can't get a really vibrant landscape from poor light on any camera. Apparantly it was nice further east on saturday, but Gwynedd has had very poor weather this week and weekend.

 

[Mentalblock]

Richard,

The first few shots I didn't cover the viefinder, but then I remembered the little cover thing that came with the camera and put it on! I didn't notice any difference between the shots though.

The filter was a cheap & unbranded ND4, and exposure times were typically 4 seconds. I did take a few at 10 seconds, but I didn't like the end result - the water was very fast moving. On live view, I passed the filter over the lens and could see the grey cast straight off, so I don't think it was exposure time or light through the viewfinder.

I've since run the images through auto levels, which brings the colours back to those taken with no filter.

I'll have to read up on this filter/ exposure balance.
I adjusted to 3 (not sure if this is stops or not) on the screen which left an almost dark screen on live view. This enabled me to extend the exposure time to get simialr results to having a filter on - well, after a few test shots which kept blowing out.




Alan,

While it was a grey day, there was plenty of light. Sunday was a lot brighter and I managed to get a few shots of a waterfall down the road - same grey problem though!


Thanks for your replies gents.
I'm thinking the problem could be filter based, so I'll be investing in a better quality filter.

 

[HoppyUK]

Could be just flare from the filter. Cheapies (uncoated ones) are prone to it, though it's usually not that bad unless you have a lot of bright sky or something.

ND4 is two stops, which is not much at all. If you want really long speeds in daylight, you need 6 stops or ten. It depends on the speed of the movement. Fountains are really quite fast and 1/15sec or 1/8sec is all you need, and probably no filter - just drop the ISO and raise the f/number. Waterfalls are also quite fast moving.

But if you want milky sea/waves or streaky clouds, you're then into the several seconds zone and a really dark filter is needed for sure then.

Getting long shutter speeds is not a problem - you just set them in manual or S. The trick is balancing the exposure correctly to them.