Reciprocity Chart for Fuji Velvia 50 RVP

One of my most favourite things to do with landscapes is to collapse many moments in time into one frame. In other words, do long exposures. I use several techniques for this, but I thought it would be good to upload a reciprocity table for Fuji's Velvia 50 RVP. percybbg2.jpg

Long exposure of the Pap of Glen Coe, Scottish Highlands

Just in case you don't know what reciprocity is, I'll explain. When shooting film, most folk think that the relationship between the shutter and aperture are always linked. They're not. As you get down to longer exposures, film loses it's sensitivity; the relationship between the shutter speed and aperture fall apart, typically once you get past 2 seconds with Velvia. Which means that if you rely on your meter, you're going to underexpose your images. So you need to compensate.

Now, you might wonder how on earth it's possible to generate an exposure that requires more than 2 seconds to expose. Even during sunrise when the light level is low, and you're shooting at f22, the meter may only say 2 seconds at the lowest range. So how is it possible to shoot for longer? Simple, I use full ND filters - often stacking up to 5 stops of ND in front of the lens, so that I end up with exposures around 30 seconds or perhaps a minute of two. Coupled with a compensation factor to make sure the exposure isn't underexposed, the exposure times will be often double that.


Click on the chart for a larger, printable version

The chart has three columns. The first shows the indicated exposure time - what the camera meter may say. The second column shows what you should actually expose at. For instance, if the meter says you should expose for 10 seconds, you should actually shot for 16 seconds. Film has lost it's sensitivity, so you are basically adding a little bit extra on top to correct for this. There is also a third column - 'Magenta CC Filter'. Velvia apparently goes a little green the longer you expose it, and the suggested way to correct this is to use a magenta filter. They come in different strengths as you can see on the graph. To be honest though - I've never seen the green cast that people talk about, so I simply don't use this column, but it's there if you feel you need it. Who knows, perhaps I'm green-blind!

So why do I want to shoot long exposures? For mystery, in order to create a scene that is a departure from reality. I love surreal images, and if I find a good landscape where the clouds are moving fast for instance, a long exposure allows the movement of the sky to be recorded. It can add a sense of movement or drama to an image. There are any other reasons, but generally, I tend to find the blurring of moving water, moving sky can radically change the experience of how we view the image.