Sunday, July 3, 2016

Basic Photography: Low light Photography

Many photographers still prefer film to digital photography. There is a considerable amount of nostalgia for film produced images. There is one area however where digital photography is well ahead of film, and as the months and years go on the gap is widening. The area where digital cameras are well ahead of film counterparts is in low light photography. There is a correlation between ASA (film speed) and ISO (digital image speed.) Whereas 800 ASA was extremely fast film, digital cameras of two iterations back had an ISO of 1600 to 3200 and now, most cameras go up to at least 12,800 ISO. While none of them perform that well at the highest ISO setting, most all current cameras function well at 3200 ISO, by that I mean, produce images with very little noise, and a lot of them do well at 6400 ISO. Sony has a full frame A7SII, that has a native ISO of over 104,000 ISO. What does all of this mean for low light photography? Well, if you have a fast prime lens, f/2.8 or faster, and a camera that performs well at 3200 ISO you can get very good hand-held low light shots. That was not possible even two or three years ago. The above image was with an f/2.8 lens at 3200 ISO. The lens is pretty sharp wide open so you get good results without a tripod.

There are essentially two ways to get good results in low light photography. One is with a fast prime
lens and a camera that functions well at a higher ISO like described above, and the other is the more traditional way, using a tripod, and using a very slow shutter speed. An example would be setting the camera at f/12, ISO 200, and a shutter speed of 5 seconds. That method will get the sharpest low light images. The image on the right was shot in that manner. If you click on the image to enlarge it you will see that the lights are starred. That is a characteristic of low light images shot manually with a narrower f/stop and a slow shutter speed. With that type of photography you have to use a tripod to keep it from blurring. Since I have an APS-C sensor I like to do a form of HDR fusion to get a greater dynamic range for my low light images. Those shooting full frame sensors have a natural dynamic range that is greater and can easily get by with one image. The secret I have discovered for doing HDR fusion with low light images is to make bracket images very close to each other, that is, less than 1/3 EV apart. The closer they are to each other in exposure brightness the less noise. I do not shoot three EV brackets. I create them with my Corel PSP X8 from one shot.

This image on the left was shot hand-held at dusk just before the sun disappeared in what is known as the blue hour. I used the same technique to create close together bracketed photos to make sure that the noise is negligible. The slightly higher dynamic range makes the photo pop and makes it easier to make it sharp. Even when it is a hand-held image shot at f/5.6 to f/7.1. When the closest object is further than 30 ft away then you get a pretty sharp image all the way to infinity. Low light images, at sunset or darker, evening city scapes and street scenes are much more interesting than images shot at high noon or mid day. The best times for interesting photos is early in the morning or late in the afternoon and evening.

One thing that you must do is experiment. You have to be willing to shoot some failures to find out how to be successful. The once nice thing about digital cameras is that you can see the results in the LCD view screen. This makes it possible to perfect what you are doing without returning to the dark room to find out what you accomplished. The other thing that I recommend is to check your exposure meter to be sure that you are at the correct exposure. When I shoot in regular daylight, I like to set my camera at -.70 EV, but not with low light shots. There I want to make sure that I am at .0+/- or if anything at +.30 EV or above. This makes the results much more appealing and avoids having images that are too dark to salvage. If you have a camera that will shoot fairly good images at 1600 ISO, and you have a fast prime, either f/2 or f/2.8, you will find that you can get some really good results hand-held... however, no matter what digital camera you have, you can use manual, a tripod and a slow shutter speed and get really good results.

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