Graduated Neutral Density Filters (Grads)
Essentially it is a rectangular, optically correct piece of resin or glass with a gradient from dark to light. It is called “neutral” because the dark part of the filter should not make any colour differences, or add a colour cast to the scene. This is not always true of cheaper filters, but the well established filter brands (Lee, Singh-Ray) leave very little colour cast on the final image.
The reason behind using an ND filter is to hold light back so that the part of the scene that is brightest (usually the sky) does not overexpose. This effect creates a pleasing image. The sky is well exposed and the foreground is correctly exposed as well.
If you were to expose the scene without using an ND grad filter, very often, the foreground would be well exposed while the sky may simply be overexposed or, if you were to expose for the sky, the foreground would be very dark.
We can do blending in Photoshop, but sometimes, you may not capture all the detail in the sky and using a filter to capture the scene may be useful. Also, you will be able to spend more time shooting and less time editing afterwards.
USED FOR
One of the most important filters for digital and film shooting, Grads are used to tame harsh or contrasty light.
Grads add shadow detail and keep color in skies at sunset which otherwise might get too bright and wash out to white. Cameras can't vary their ISO from point-to-point as our eyes can.
Grads add shadow detail and keep color in skies at sunset which otherwise might get too bright and wash out to white. Cameras can't vary their ISO from point-to-point as our eyes can.
EXAMPLE PHOTO OF THE WASH OUT TO WHITE
If you measure the exposure at the bottom of the photo, the sky will wash out to white. If you measure the exposure at the top of the photo (sky), The the bottom of the photo becomes very dark.
Solution
Let's use a Graduated Neutral Density Filters
How do I use an ND grad filter ?
① Set up your camera on a tripod and take a light meter reading of the foreground. Making sure that your camera is on Manual, point it down and fill the viewfinder with the foreground to take the reading.
② Take a light meter reading in the same way as above, of the sky.
③ Work out the difference between the two exposures and use an ND Grad to get your scene to within one stop of light difference. As an example, if the sky is three stops brighter than the foreground, you can use an ND Grad that blocks two f-stops of light or a 0.6 ND Grad.
④ Slide the ND grad filter into place in front of the lens and determine the best position for the gradient to be in your image. If it is a hard horizon (i.e. a seascape scene) use a hard edge grad, if it is a forest scene, use a soft edge grad.
⑤ Expose for the foreground and make the shot.
⑥ Check the result on the LCD screen, zoom in on the image to make sure everything is properly exposed. Make any adjustments and shoot another image if necessary.
The angle of the filter can be adjusted.
Example photo with a graduated filter
Oct 2015 Montepulciano, Italy - 1/6 sec f11.0 ISO 100 18mm
Montepulciano (“mon-ta-pull-channo”) is a medium-bodied red wine grape that is supposed to have originated in central Italy. Montepulciano wines are commonly confused with Vino Nobile de Montepulciano, a regional name for the Sangiovese-based wine in Tuscany.
Montepulciano is a medieval hilltop town in Tuscany, Italy. Surrounded by vineyards, it’s known for its vino nobile red wine. The Torre di Pulcinella is a clock tower topped by a figure of the Pulcinella, a commedia dell’arte character. On the Piazza Grande is the 14th-century Palazzo Comunale, with a tower offering views of the surrounding countryside. Also here is the Duomo, with a huge triptych above its altar.
Montepulciano is a major producer of food and drink. Renowned for its pork, cheese, "pici" pasta, lentils, and honey, it is known worldwide for its wine. Connoisseurs consider its Vino Nobile, not to be confused with varietal wine made from the Montepulciano grape, among Italy's best.
The distance between Rome and Montepulciano is 145 km. The road distance is 176.1 km. Montepulciano is on a minor rail line and the small train station is a few kilometers outside of town. Buses connect the train station with the town. Hourly buses run from Chiusi train station, on the major rail line between Rome and Florence and probably more convenient, to Montepulciano.