Using a CPL and an ND filter

[danski]

I've just bought a Hoya HD CPL filter and a Light Craft ND500 filter (based on Hoppy's good review) but not entirely sure if I understand how to use them correctly.

I'm off to Spain next week and was hoping to go down to a spot on the coast that I know well and should be perfect for shooting with the ND fitted. Am I right in thinking that I should do the following:

1. Set up tripod and compose shot (will have a mixture of rocky bay, cliffs and open water & waves crashing on rocks)
2. Set aperture (thinking f/8-f/11) and ISO (100?)
3. Focus manually
4. See what shutter speed is suggested by camera without ND filter on
5. Attach filter then drop shutter speed by 9 stops
6. take photo using mirror lock up and remote release
7. Maybe also take a few more shots bracketing exposure +/- 1 or 2 stops

No idea how to use the CPL (it hasn't arrived yet) - but I'm assuming that it rotates to let me decide how much of an effect I want it to make?

I'll probably be attaching these to either my Tokina 12-24 or my 24-105L for the shots and shooting around sun down, although the light will still be fairly strong

any tips/recommendations much appreciated

thx

 

[HoppyUK]

Sounds about right. Make sure you cover the viewfinder eyepiece - light can get in there and creep around the mirror on a long shutter speed.

Your first exposure will likely be something of a calculated guess. Your filter might not be exactly nine stops (all dark NDs vary a bit, mine is about 8.3 stops) plus lots of other small factors that can add up and skew things. But you'll not be far out. Adjust to taste.

To save time getting the right exposure on a long one, crank the ISO right up for test shots and turn the noise reduction off.

If you want the JPEG to be spot on for colour, do a custom white balance. Again to save time, I do a quick white balance before hand (in the same light obviously) and keep that sample shot on the card so I can go back to it any time to reset. If you shoot Raw, then no worries anyway - correct in post, though that filter is not far off neutral.

With the polariser, just fit it and rotate for best effect, and shoot as if it wasn't there.

 

[Yardbent]

I'll probably be attaching these to either my Tokina 12-24 or my 24-105L for the shots and shooting around sun down, although the light will still be fairly strong

I "think" the CPL works best at 90degrees to the sun....so you may not see any effect taking sunsets ......try it and see !

 

[boyfalldown]

I'll probably be attaching these to either my Tokina 12-24 or my 24-105L for the shots and shooting around sun down, although the light will still be fairly strong

I "think" the CPL works best at 90degrees to the sun....so you may not see any effect taking sunsets ......try it and see !

the polarising effect is strongist at 90 degrees.You should still see an effect with a sunset though

 

[markw08]

I've just bought a Hoya HD CPL filter and a Light Craft ND500 filter (based on Hoppy's good review) but not entirely sure if I understand how to use them correctly.

I'm off to Spain next week and was hoping to go down to a spot on the coast that I know well and should be perfect for shooting with the ND fitted. Am I right in thinking that I should do the following:

1. Set up tripod and compose shot (will have a mixture of rocky bay, cliffs and open water & waves crashing on rocks)
2. Set aperture (thinking f/8-f/11) and ISO (100?)
3. Focus manually
4. See what shutter speed is suggested by camera without ND filter on
5. Attach filter then drop shutter speed by 9 stops
6. take photo using mirror lock up and remote release
7. Maybe also take a few more shots bracketing exposure +/- 1 or 2 stops

No idea how to use the CPL (it hasn't arrived yet) - but I'm assuming that it rotates to let me decide how much of an effect I want it to make?

I'll probably be attaching these to either my Tokina 12-24 or my 24-105L for the shots and shooting around sun down, although the light will still be fairly strong

any tips/recommendations much appreciated

thx

Reference step 4

Would you take reading from a mid tone area say the rocks or the sky???

 

[boyfalldown]

Reference step 4

Would you take reading from a mid tone area say the rocks or the sky???

I'd matrix the whole scene. I think exposure is enough of a calculated guess with these not to need to worry about metering of a given area

 

[HoppyUK]

the polarising effect is strongist at 90 degrees.You should still see an effect with a sunset though

To check the effect of a polariser on blue skies, form a 90 degrees angle with your thumb and forefinger, and point it at the sun like a gun. Rotate your forefinger and your thumb points towards the area of strongest polarisation.

With a sunset and the sun therefore close to the horizon, the sky will be most darkened directly above you, so not much help there really.

I'd matrix the whole scene. I think exposure is enough of a calculated guess with these not to need to worry about metering of a given area

Yes, agreed.

The main reason why the final exposure is hard to calculate is because of the optical vignetting effect you get when using a dark ND filter with a wide lens.

With a wide angle, the lens is looking through the filter at an angle towards the edges, effectively making the filter progressively thicker and therefore darker. Nothing you can do about that, except moderate the final exposure level to try and optimise it.

Sometimes the effect is quite attractive, but if you want to get rid of it in post processing, be aware that when shooting with a super-wide the corners might be two or three stops down on the centre. When you try to pull them up in post, you are effectively raising the ISO very considerably and you get noise.

So, shoot at lowest ISO and push the exposure as much as you dare without over exposing - enable blinkies (highlight over exposure warning, in the menu). Basically a bit of 'expose to the right' on the histogram technique is what's called for.

Or just zoom out a bit, that reduces it

 

[danski]

thanks for the comments all - hadn't thought about covering the eyepiece up Hoppy, but will make sure I do.

will follow your advice and see what results I get - will be sure to post up here for all to see (& comment on!)

 

[danski]

With the polariser, just fit it and rotate for best effect, and shoot as if it wasn't there.

Are you suggesting that I should just leave it fitted to the lens for general bright daytime shots, or just fit it for the occasional shot where I'm looking for extra saturation or minimise reflections?

 

[HoppyUK]

Are you suggesting that I should just leave it fitted to the lens for general bright daytime shots, or just fit it for the occasional shot where I'm looking for extra saturation or minimise reflections?

Since you've got that nice Hoya HD polariser, high quality and only a stop-and-a-bit of light loss, I would leave it on most of the time. That's what I do pretty much. There are very few landscapes that don't benefit from a polariser, or most other things for that matter. At worst, it mostly does nothing.

Situations to watch out for. Very bright blue skies, they can go black. Shiny sun-tanned skin on the beach, can go a bit dull like putty. Sun on water, most of the brightness and colour comes from the sky and a polariser can kill that and make the water look too dark, even if you can see the fish.

Of course you can see all this happening, so rotate the filter to moderate, or take if off. Bear in mind the 90 degrees rule, which means that as you rotate, reflections in one dimension are reduced and at right angles to that they are progressively allowed through. And the optimum angle for killing reflections is 37 degrees to the surface.

Try this. You don't need a camera, just make sure you're looking though the filter the right way (a circular polariser does nothing if used back to front). Stand next to a shiny dark car in bright sun, about three-quarters front view. With the mark at the top, reflections will be reduced on the bonnet, windscreen and roof. Give it a twiddle for the optimum spot, it's quite critical. Very useful for motorsport that.

Along the sides of the car, reflections will be allowed through but as you rotate the filter 90 degrees they will begin to disappear while those on the bonnet will start to come back. Now with the reflections on the side reduced to max, move up and down the car and you will see the reflection beginning to come back as you move away from 37 degrees to the surface. This angle isn't so critical as the rotation but by the time you get fully square on to the surface the reflections will be fully back regardless of the rotation.

The only other thing to say is that polarisers only work on reflections off non-metalic surfaces. It's an electromagnetic radiation thing, do with the conductivity of the material. Which also means that, in theory, a polariser works slightly differently on salt water. Being a sad b****r, I just tried that and it's actually true! But the difference is very, very slight Never done that before. Polarisers are magic.

With that information, and the forefinger and thumbs trick, which is very handy (see what I did there?) you're fully armed (and again!)

 

[danski]

A big thumbs up to you Hoppy (carrying on the theme!).

Another quick question - if the polariser is knocking off about 1.5 - 2 stops of light does that mean that I should over expose by the same amount or will the camera automatically adjust? I'm shooting RAW by the way

thanks again

 

[HoppyUK]

A big thumbs up to you Hoppy (carrying on the theme!).

Another quick question - if the polariser is knocking off about 1.5 - 2 stops of light does that mean that I should over expose by the same amount or will the camera automatically adjust? I'm shooting RAW by the way

thanks again

The camera will automatically compensate. Evaluative metering is best but as always you may want to tweak that after checking the LCD/histogram/blinkies.

BTW, your Hoya HD polariser only reduces the overall exposure by 1.2 stops, not the normal 1.7-ish that you get with most polarisers, that's its main advantage - hence you can leave it on most of the time with minimum light loss penalty.

Of course the exposure will get reduced by much more than 1.2 stops in some areas of the picture, depending on the amount of polarised light there is, but that's what you want. The camera's meter will always get you close, so just moderate it to taste.

 

[danski]

just arrived today - been out and take a few shots on both the 12-24 and 24-105 - me likes a lot hehe

does wonders for foliage - gives it a real pop

fun times ahead

thanks again hoppy