Basic questions re filters and exposure

boccers_2000

boccers_2000

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Name
Andrew
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Hi Guys,

I have a Cokin Filter (ND4) and a 500D.

I just want to know how you actually go about using them? Do I expose for the foreground, lock the exposure, put the filter in then shoot?

Or does the filter go in, expose for the foreground then shoot?

I'm not even sure how to lock the exposure once I have focus.

Any help much appreciated
 
For what it's worth, I attach the filter and then focus and get exposure using matrix metering; seems to do the job.
 
Every filter should have an exposure factor printed on the side of the filter - that is the number of stops (if any) you need to increase exposure by to take account of any light loss caused by the filter.

In the days before TTL metering you needed to meter as usual - then manually add the exposure compensation to allow for the filter. Nowadays if we're using a TTL metering system the filter is on the front of the lens so allowance is automatically made for the filter as the metering system is reading light which has passed though the filter, so we don't really need to worry about it.

If you want to be really pedantic about it there's an argument for still adding the compensation manually as meters can be more sensitive to some colours in the spectrum, so depending on the colour of the filter you might be better advised to add the exact filter factor increase rather than relying on the meter.

Filter factors are usually marked 1.5X (half a stop increase)

2X (1 stop increase)

4X (2 stops increase) and so on....
 
Nice one, thanks for that.

Well it would appear that I simply slide the filter on, expose for the foreground (ie where there is no colour in the filter) and then take the picture and let the darker top side of the filter do its work.

I would have thought that spot metering (ie focussing on the foreground) would work beter as surely, evaluative exposes for the whole scene so if I put the filter on then meter the foreground will be darker as it is also taking account of the dark part of the filter.

I'm prbably talking absolute nonsense and will be swiftly rebuked but im just trying to figure out how that works as I thought filters were there to allow the foreground to remain brighter and stop the sky being blown out (well ND Grad filters anyway)
 
I too am wondering the same thing!
Hope you dont mind me jumping on your bandwagon here...
When using a grad or non grad filter, lets assume ND4 for this example - is the amount of light blocking precise? I mean, it is supposed to be a 2 stop filter - so if you exposed for say 1second without the filter and then 4seconds with the filter the resulting image exposure would be the same?
 
The ND4 is a grad filter - basically stick it on the front, it should reduce the brightness of the sky (assuming the sky is lined-up with the filter...which is a big assumption) and meter as you would otherwise.

The only filters which you have to meter and calculate before putting the filter on are things like 10-stop ND filters - simply because they let so little light through the camera can't figure it out!

For carefully composed landscape shots on a tripod (the ones you are going to use a Grad ND on) you should be using Spot Metering not Matrix/Evaluative/etc - there's just way too much randomness and inconsistency from shot to shot if you let the camera do it. What happens if (say) a car goes past and reflects a spot of light - the whole scene could be suddenly underexposed.

Don't know how your Canon works, but all decent cameras have the ability to lock exposure (look for a button marked AE-L or something...may need to configure menus so its a case RTFM I'm afraid...)
 
flossie said:
The ND4 is a grad filter - basically stick it on the front, it should reduce the brightness of the sky (assuming the sky is lined-up with the filter...which is a big assumption) and meter as you would otherwise.

The only filters which you have to meter and calculate before putting the filter on are things like 10-stop ND filters - simply because they let so little light through the camera can't figure it out!

For carefully composed landscape shots on a tripod (the ones you are going to use a Grad ND on) you should be using Spot Metering not Matrix/Evaluative/etc - there's just way too much randomness and inconsistency from shot to shot if you let the camera do it. What happens if (say) a car goes past and reflects a spot of light - the whole scene could be suddenly underexposed.

Don't know how your Canon works, but all decent cameras have the ability to lock exposure (look for a button marked AE-L or something...may need to configure menus so its a case RTFM I'm afraid...)
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Thanks!! That explains it. I guess the confusion just comes in how the process works ie what sequence of events you would go through once you find the spot where you want to take the picture ie (a) set up tripod (b) place camera in tripod (c) put Cokin adapter ring/filter holder on end of lens....

Feel free to finish it off, i'm interested to know how you go about actually doing it.
 
Are these better than buying specific sized filters from eBay etc?

So if I bought the holder from jessops - I would need to buy 3 adaptor rings to fit the different sizes of my 3 lenses (assuming I wanted to use a filter on each of my 3 lenses that is..)

Where did you buy the filter from? And did you use rectangular?
 
futureal33 said:
Are these better than buying specific sized filters from eBay etc?

So if I bought the holder from jessops - I would need to buy 3 adaptor rings to fit the different sizes of my 3 lenses (assuming I wanted to use a filter on each of my 3 lenses that is..)

Where did you buy the filter from? And did you use rectangular?
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I only bought a 77mm adapter ring (as I have a 10-22mm lens). I think youd need 3 different adapter rings for the different lenses and not sure about the holder (as the one i bought was specifially for wide angle).

The Filter is rectangular. Ive only used it once, last weekend. The pic below was the result (although I'm not sure if it had an effect or not but I think it helped blue the sky a touch).


Pentlands 1 by boccers, on Flickr
 
futureal33 said:
Thats a really nice photo, the blue sky is superb!
Is your filter a genuine Cokin P one from Jessops?
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It sure is. I'll be buyinh an ND8 soon though.

Lots of people complain about Cokin (say there is a colour cast in it). Personally, I haven't noticed.

One other system is the Lee filters. Much more expensive but much greater optical quality. Expensive because they are all hand made but you cant buy them in all of the shops, just a few specialist ones etc
 
futureal33 said:
Im guessing the likes of something like this http://cgi.ebay.co.uk/ND2-ND4-ND8-N...es_CameraLensesFilters_JN&hash=item336553cd2a would not be so good quality?
Click to expand...

If they are genuine then they will be fine. The guys feedback is good so maybe you can chance it. These are ND filters as opposed to NDGrad filters though (ie the whole thing is coloured as opposed to half being coloured and half not.

The Grad allows you to keep the foreground light whilst stopping the sky from being blown out. The simple grads ie those on the ebay site apply that over the whole scene
 
Cheers Andrew, my intention was to use 2 in conjunction with each other... A solid ND4 or ND8 to darken the whole image to allow me a slow shutter speed (to achieve that misty running water effect) and then using a grad ND4 filter to ensure the sky doesnt get blown out with the longer exposure.

Its my understanding that a solid ND filter will allow the same EV but with a longer shutter speed... so even with a solid ND filter and long exposure the sky may still be blown out (as with a normally metered photo where the sky is a lot brighter than the rest of the image) so hopefully the grad filter would tone that down a bit!
 
futureal33 said:
Cheers Andrew, my intention was to use 2 in conjunction with each other... A solid ND4 or ND8 to darken the whole image to allow me a slow shutter speed (to achieve that misty running water effect) and then using a grad ND4 filter to ensure the sky doesnt get blown out with the longer exposure.

Its my understanding that a solid ND filter will allow the same EV but with a longer shutter speed... so even with a solid ND filter and long exposure the sky may still be blown out (as with a normally metered photo where the sky is a lot brighter than the rest of the image) so hopefully the grad filter would tone that down a bit!
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No problem. The holder I got doesnt allow for stacking so id be careful to get one that d Nickoes.

I rekon just pop down to your local Jessops/Jacobs and speak with someone about your needs. Thats what I did.
 
I'm not sure why you're worrying about locking the exposure Andrew? this is a classic situation where you'd be far better off shooting in Manual mode.

Meter for the foreground and set the exposure. Recompose your image to include the desired amount of sky and mount your grad filter. Take the shot. All you have to be aware is any sudden light changes during this process, in which case obviously you'd start again.
 
CT said:
I'm not sure why you're worrying about locking the exposure Andrew? this is a classic situation where you'd be far better off shooting in Manual mode.

Meter for the foreground and set the exposure. Recompose your image to include the desired amount of sky and mount your grad filter. Take the shot. All you have to be aware is any sudden light changes during this process, in which case obviously you'd start again.
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Thanks! Apologies if the questions seem to be all over the place. Im relatively new and all the information can at times confuse.
 
boccers_2000 said:
Thanks! Apologies if the questions seem to be all over the place. Im relatively new and all the information can at times confuse.
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LOL THat's OK - it's quite understandable. Don;t forget you have the best tool at your disposal with the preview screen on your digital camera . Test shots cost nothing. ;)
 
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