As with all things photographic there tends to be differences of opinion and the occasional hard-edged viewpoint that people bring to on-line discussions. Shooting in low light is one such subject. Many folks have a strong belief that if you shoot in low light you must use a full frame camera to get good results. Period.
But… is this actually true?
Note: Click on images to enlarge
Of course in situations where a tripod is used any camera, regardless of its sensor size, will operate at its optimal since the lowest possible ISO can be used. Shutter speed and aperture can then be adjusted to achieve the best possible exposure and composition in terms of depth-of-field. So, let’s take tripod shooting off the table and focus on situations where a photographer is forced to shoot hand-held in lower light conditions, and is using a smaller sensor camera like a M4/3 or the Nikon 1 CX format.
If we simply look at sensor test data there is absolute truth to the notion that full frame sensors are better than smaller sized sensors when shooting in low light conditions. Dynamic range and colour depth are both higher. And, the key point for many photographers is that digital noise is much better controlled as higher ISO’s are used.
All we need to do is examine sensor test data on the DxOMark web site to see the facts in black and white. A camera like my Nikon 1 V2 has a ‘sports score’ (i.e. the low light score) on DxO of 403 ISO while a camera like the Nikon D750 scores 2956 ISO. There’s nothing to debate – facts are simply facts. The D750’s sensor scores almost 3 stops better than the sensor in my Nikon 1 V2. And, it is also true that smaller sized sensors ‘top out’ at much lower ISO values than do their full frame brothers. For example, my Nikon 1 V2 doesn’t even have an option to shoot higher than ISO-6400.
So, all things being equal with the exposure triangle – there’s no doubt that a full frame camera will blow the doors off of a small sensor camera like my Nikon 1 V2 when it comes to shooting at higher ISO’s.
What we often overlook with these types of discussions are some practical, everyday shooting considerations. As I illustrated in an earlier article there are some very practical depth-of-field advantages when shooting with a smaller sensor camera system like the Nikon 1.
This difference changes one of the factors in the exposure triangle in terms of aperture setting. Someone using Nikon 1 system gear can create a similar image to someone using full frame gear by using a more wide open aperture and this could allow them to shoot at a lower ISO than the full frame shooter. Obviously this could come in handy when shooting in lower light situations.
Of course, this assumes that the Nikon 1 shooter has an appropriate native CX lens that can be used in that specific situation. While the Nikon 1 lens family is growing there are still a number of gaps that owners need to work around as best they can.
Owners of M4/3 cameras have a better selection of fast prime and zoom lenses available to them. They are currently in a better position to use a more wide open aperture to help reduce the ISO’s at which they shoot, while still achieving their desired depth-of-field when compared to using a full frame camera.
For example, GH4 owners have two very good Panasonic f/2.8 constant aperture zooms available (12-35 mm and 35-100 mm).
Let’s assume that a photographer was using a Nikon D750 full frame camera with a 70-200 mm f/2.8 constant aperture zoom, and was shooting at f/5.6, 1/200, ISO-3200, at 200 mm in order to achieve their desired depth-of-field, exposure and image framing.
Faced with exactly the same lighting conditions, distance from subject, desired field-of-view and depth-of-field, a GH4 owner could shoot at 100 mm at f/2.8, 1/200 and only have to use ISO-800 to get their image. This is because the aperture they are using is 2-stops faster than the one being used by the D750 owner. Since the GH4’s low light score is 791 ISO and the D750’s is 2958 ISO (as rated by DxO) both set-ups would likely produce very similar levels of noise in the images each camera produced under identical low light conditions.
When shooting with a smaller sensor camera it is important to remember that the sensor crop factor can allow us to shoot at more wide open apertures when compared to photographers using full frame gear and that may allow us to use a lower ISO while still getting the desired depth-of-field and framing in our images. This is due to the fact that smaller sensor camera systems can use shorter focal length lenses to achieve the same field-of-view as full frame cameras. And, shorter focal length lenses have deeper depth-of-field characteristics regardless of the sensor size on the camera on which they are used.
Another very important consideration when shooting in lower light conditions is the size and weight of various camera systems and how that can potentially impact a photographer’s ability to effectively shoot hand-held. In the next portion of this article let’s have a look at some hand-held test images.