Graduated Filter using Technique?

[ramesh]

I have been using Nuetral Graduated filter(cokin) for nearly 2-3

years for landscape photography. I am happy it helps in reproducing

those overwhelming overhanging clouds. This is the procedure that I

follow.

 

1) Spot meter the foreground. Compensate for the nuetral tone(Ex:

mountain)

 

2) Hold the Nuetral Graduated filter in front of the lens.

 

3) Slid the filter down so that dark part of the filter covers the

sky. As slide the filter, I can see underexposure marker kicking

down.

 

This underexposure marker bothers me and rises doubts about my

technique. I have following doubts and need clarification.

 

a) Should I be compensating (by 0.5 stop) for filter?

 

b) Should I have to put the filter and then spot meter the

foreground?

 

I would like to hear how others use this filter.

 

 

Thanks

 

Ramesh

[marshall]

Generally, I'll spot-meter both sides of a scene that's a good candidate for using an ND grad. For example, in a fall color reflection, I'll meter both the actually object and it's reflection to measure the difference between them. Then, I'll decide the appropriate amount of filtering (not always making it the same level, as that sometimes looks unnatural), bringing, say, the top part of the image down closer to the reflection. Usually, I'll still bracket exposures, but the initial exposure setting comes from knowing the original reading and the strength of the ND grad.

 

Someone else may come in and explain a better way to do this, or at least explain it more coherently than I am in a tired state. Onward.

[pvp]

I'm also not the most confident with grads, but my understanding is that you need to meter the part of the scene that will NOT be affected by the dark part of the filter, i.e., the foreground.... so you're OK there I guess. There may be a slight compensation needed even for the clear part of the filter, perhaps 1/3 stop. Ignore the meter when the filter is in place.

 

The problem I have with ND grads is seeing where the darn edge is. I'm using the Cokin P120 and P121 grads. The edge on them is so soft that I can't tell where it is most of the time.

[jim schwaiger]

I don't have a spot meter, but I use a center weighter meter to do the same

thing. It may actually work better because it takes into account more of the

area. I simply point to the sky and then the ground to see how many stops

difference there is.

 

To place the filter, stop the aperture down using a DOF preview (or do it

manually). This will help you see the effect much better.

 

If you meter for the darker area and keep that setting, you should be fine, but

there is nothing wrong with metering while the filter is in place. I would not use

the spot meter in this situation, the scene may be too dark to accurately

choose a mid-gray area, use matrix or center-weighted instead.

[stephen hazelton]

It seems to me that if you're happy with your results, that should answer the question. If you're using color print film, it probably wouldn't much matter how you metered it; center-weighted through the filter would probably do okay. With slide film, it should be fairly obvious if you're off much on the metering.

[jonathan_bundick]

As too metering the frame, I have used either of these two methods with success.

 

(1) Meter a mid-tone that falls in the clear portion of the filter. Place it where you want it in terms of tonal value, and bracket +/-1/2 stop around that value. When shooting 35mm, I sometimes place this value as a mid-tone, and 1/2 stop below. In some shots one turns out better than the other, and 35mm is cheap. For 4/5 I just shoot 2 frames at the same exposure, and develop one. Judging from that I know if I want to push or pull the other frame to yield what I want.

 

(2) If shooting 35mm with an evaluative mode, just let the meter determine the exposure, and bracket +/- 1/2 stop around that. This usually yields acceptable results, if not exactly what you want.

 

With both of these methods you will already have to figure out how much filtration you need. 1 stop, 2 stops, 3 stops or more. For this I spot meter the brightest highlight in the filtered portion of the frame, and the prominant mid-tone in the unfiltered portion of the frame. If these values are seperated by more than 2 1/2 stops, you need to use the grad. How much is more a matter of personal taste than anything else.

 

Since you are using a rectangular filter holder I have a very precise way to determine where the filter needs to be positioned. You must be using a tripod for this to work. First frame the scene the way you want. Second you will need to cut a bit of cardboard the same size as your filter. Slide the cardboard down the filter holder until it lines up with where the filter needs to be.(lens must be stopped down to taking aperture for this to work correctly). Replace the cardboard with your filter, placing the portion of the filter that almost completed the transition to dark at the same place as the bottom of the cardboard. Before I started doing this it was very hard, even with the lens stopped down to figure out where the transition should go, and I ended up with allot of missed shots. Since I started using this technique, I haven't missed a one. The transition is always where I wanted it to be.

 

Best wishes,

Jonathan

[ramesh]

Thanks for the cardbord idea and also for documenting precise steps.

When you use Polarizer + Filter holder + Graduated Filter, do you get vignetting?

I get vignetting while using such combination. So sometimes I hold the Graduated Filter in hand without filter holder. By doing this I avoid vignetting.

 

Regards,

Ramesh

[pvp]

<I>...you will need to cut a bit of cardboard the same size as your filter.</I><P>

Thanks from here, too... That has got to be the most useful bit of invention I've found in many an hour wasted in front of this monitor. You, sir, are a bona fide, steely-eyed photo man.

[imaginator]

I have never used one, but I've been considering different choices. My plan is to use one much larger than needed so I can move it up/down as needed (and I might even have it suspended in front of the lens... not touching it, but that's another story) As others have said, the obvious method is to meter the part of the scene where the filter has no effect (or very little) but since the sky will ultimately be part of the final image, you still have to make compromises between sky and scene (unless you have a bunch of various grads) so it becomes more subjective, and bracketing is still needed (for slides) There are a few unique situations in night photography that I might use one upside-down, or for other purposes besides standard sky dimming, but I doubt that would interest you (this is also why I need it mounted independent of the lens... so I can remove it during a long exposure without jiggling camera)

[jerry_tostevin]

Hi Ramesh,

 

I know others have already commented on their techniques - I use the same technique as John Shaw after reading one of his books which discusses the topic. I personally use the Hi Tech filters in the Cokin P holder, I decided to stay away from the Cokin ND graduated filters because I believe they're not actually true neutral density and have a colour cast (so I've heard). I'd be interested to know what your experience is with them. My technique is as follows;

 

Suppose you're shooting a landscape shot with snow-capped mountains in the background and some plant life in the foreground. Suppose the mountains are in bright sunlight but your foreground is in shadow. Suppose the foreground area averages out to a medium-tone (using your spot meter readings). Then spot meter the brightest area of your picture which is the snow on the mountains in bright sunlight. You discover that the difference between the 2 areas is 5 stops of light. If you want the snow to be rendered as a very light tone (approx. 2 stops lighter than medium) on film and the foreground to remain a medium tone, you need a 3 stop graduated ND filter.

 

The way I meter for this is to put the filter in the holder with the grey section covering the lens. I then meter the brightest part of the scene through the ND section and dail in +2 stops of exposure compensation (this way I know that I will correctly render the white as a true white on film, even if the filter doesn't cut the light coming through the lens by exactly 3 stops - I'd rather have a medium toned area turn out a little under or overexposed rather than the brightest area). But hopefully your filters will limit the amount of light by the exact factor that they are supposed to.

 

I say this because I know my Hi Tech filters aren't the exact factor they claim to be (ie. my 2 stop ND filter is actually a 2 1/3 filter factor and my 3 stop is actually a 3 1/3 stop filter factor). I know because I've performed metering tests on my filters when I got them - I suggest you do the same with yours to check. I know that the Singh Ray filters are supposed to be exactly what they say they are, but they're also very expensive.

 

Anyhow, I then align the filter appropriately in the holder so the graduation line starts where it needs to and take the picture.

 

I hope this helps - happy shooting.

[ramesh]

While using ND filter, I have observed change in color of the subject. But I can not blame this on ND filter alone for following reason.

 

1) I see color shift in foreground. If I have not properly selected the midtone object for metering, color could have shifted.

 

2) I see some color shift in the sky/background (where darker part of the ND filter sits). This color shift could be beacuse of transition area in the soft ND filter. I will be able tell this when I use

 

3) In most of the cases I will be using polarizer & ND filter.

Polarizer could also have affected.

 

I think best way to clear(for my satisfaction) is to buy the expensive singh-ray filter and try it.

 

You have different approach to metering. Your technique suggest you would rather underexpose the foreground than overexpose the highlights. My approach is that I would rather over expose the highlights than underexpose the foreground.

 

I need refine technique too. I always use 2 stop for all situations. I think I need to start using appropriate ND filter for each situation. I would like to try hard edged filter too and also your technique of starting with highlights.

 

 

 

 

Thanks

Ramesh