It’s a long-discussed topic: full-frame or crop-sensor camera, which is best? Well, there are a number of variables to consider, and some might surprise you! In this article I’ll look at some of the key ones and how they benefit (or don’t!) macro photography.
What is Full-Frame?
Long before digital cameras came along, most popular film SLR cameras captured an image that was 36mm by 24mm. When digital cameras were invented it just wasn’t very affordable to give the camera a sensor of that size, so they made a smaller version. This smaller image-capture area became known as a "crop-sensor" camera, and the old standard 35mm format became "full-frame."
Nikon has two sensor sizes: full-frame (marked with an FX) and crop (DX); and Canon has three: full-frame, 1.3x and 1.6x
For demonstration purposes in this article, I’ll use the Nikon D800 (FX) and Nikon D90 (DX) and specify the lens used for each picture.
Same Lens, Different Image
If you think about putting the same lens on both a full-frame and a crop-sensor camera, the results would obviously differ. The crop-sensor would appear ‘larger’; that is, more magnified. I say appear larger because it’s not actually magnified, the field of view is just restricted. When you display the full and crop images at the same size (as below) you get a cropped-in view with the smaller sensor.
Full-Frame, Crop-Sensor and Macro Photography
So let’s take a look at how the decision to use a full-frame or crop-sensor camera plays out in macro photography.
Image Quality
Sensors consist of light gathering spots called photosites. Understanding the difference between a photosite and a pixel fuses my brain, but the best way I’ve seen it expressed is this: ‘photosite is to sensor as pixel is to picture’. The photosite collects light, which creates an electrical signal. An analogue-to-digital converter takes that electrical signal and turns it into a digital value (or a bit of math, in other words) that represents the amount of light that hit each photosite. We call this value a pixel. So, you can think about a photosite in terms of the amount of light captured on your sensor and a pixel in terms of what you view as the output (the picture).
A camera with a larger sensor can take on more light—more information—which is why full-frame cameras usually take better quality images than crops. If two cameras have the same amount of photosites but two different sensor sizes, the one with the larger sensor usually produces better pictures.
Low Light Performance
As described above, a larger sensor generally means better low light performance when using high ISOs (if other variables are the same), and if you’re zooming in to capture a small object (and probably using a large aperture) then that’s a definite boon for macro.
Bigger light sensors capture more light so you’ll generate less noise. The photosites are generally larger on a full-frame sensors, too, and that means each photosite can receive more light. More light means less amplification is needed to produce an acceptable image, which in turn means less noise.
Focal Length ‘Magnification’ or Field of View
If a crop-sensor appears to magnify the image, and we know that macro photography is all about close-ups, then this is obviously going to be a distinct advantage. Landscape photographers tend to prefer full frame cameras because you can get wider field of view in the image. Wildlife photographers often prefer a crop sensor as you get a more narrow view out of your lens’ focal length.
Here I shot at the same distance, hand-held with roughly the same settings. You can see that the crop appears to get much ‘closer’ to the plant but I think the sharpness to blur ratio of the D800 is much more pleasing. You need to consider that the plant was blowing in the wind for both shots though so it was probably more luck than judgment to get anything in focus!
Depth of Field
This obviously depends what you’re going for. Wider apertures on a full-frame camera provide a much more blurred background than a crop-sensor. This is to do with the focal length, the aperture and the distance you are from the subject: all things that are influenced by which sensor you have. If you’re looking for an artier, shallow depth of field then a full-frame works better for this. If you want everything crisp and in focus then you don’t have to stop down a crop camera as much as you would if you were using full-frame. With macro photography you could be after either look depending on your subject and your personal style.
Weight
Probably one of the least considered options but, in my opinion, one of the most important. Full-frame cameras are naturally bigger than crops and so, heavier. If you shoot macro hand-held as I do then you’ll know how difficult it can be to keep the camera steady at a long focal length, especially if you’re crouching down on the ground at the same time! The weight of the camera can really affect your ability to hold it properly and I find it much easier to compose and shoot quickly with the D90 than the D800.
Lens Compatibility
Using a ‘full frame’ lens on a crop camera is fine, you’ll just see a restricted field of view; again, that apparent ‘magnification’. However, put lens designed for a crop sensor onto a full frame and you’ll get a considerable vignette around the outside, as it just won’t fill the available space. It’s still usable, you’d just need to crop your photo in post-production. It does mean you should consider which lenses you have already and whether they’re compatible with a full frame camera, should you decide to make the switch.
In Summary
It’s easy to think you’re missing out on something if you have a crop-sensor camera rather than a full-frame, but it really depends what you’re using the camera for and how you use it. For macro, consider the following:
- Crop-sensor images appear more magnified due to the restricted field of view
- Full-frame cameras generally handle a higher ISO, and therefore low-light situations, better
- A shallow depth of field is easier to achieve with a full-frame camera
- Crop sensors are much lighter and therefore easier to manoeuvre and keep still
- Lenses made for crop won’t work as intended on full frame
You can take great macro photos with a crop-sensor or a full-frame. One size sensor does not far outperform another for macro photography. But, before making the move to one or the other and buying lenses, consider the benefits and downfalls of each and make informed decisions. If you can, it’s worth borrowing the camera first so that you can try it out, test its weight and see the quality of images you can get with it.
