Another difference to note between Four Thirds and full-frame or APS-C format sensors is their aspect ratio. The Four Thirds sensors in Micro Four Thirds cameras have a 4:3 aspect ratio, while full-frame and APS-C format sensors have the same 3:2 aspect ratio as 35mm film.

The idea of dark field imaging is simply to use a large light behind the subject, but then block out a small portion of the light with a “dark field patch” between the subject and the light. The camera is then positioned such that the field of view is slightly smaller than the patch, so the background of the image is flat black and no light goes directly from the source to the lens.

For instance, if you’re shooting with a Nikon Z50 (an APS-C camera) and a 35mm lens, the 1.5x crop factor means the lens behaves like a 50mm (actually 52.5mm) optic would on a full-frame Nikon Z6 III. However, at any given aperture setting, a 35mm lens captures greater depth of field (a bigger in-focus area) than a 50mm lens. This means that you need a wider aperture on the 35mm with the Z50 to capture the same depth of field on the Z6 III with a 50mm lens.

While larger sensors offer advantages in terms of image quality, pixel count and depth of field control, they come with trade-offs. For a start, the sensor is typically the most expensive component in a camera, so opting for a full-frame model usually means a significant increase in cost. Full-frame lenses also need to produce a larger image circle, making them bulkier and more expensive than their APS-C or Micro Four Thirds counterparts. In some cases, there’s not a significant difference in the size of cameras with different-sized sensors, but the bulk and weight saving made with Micro Four Third and APS-C format lenses can be very significant.

This graphic shows the relative sizes of the different sensors and the image circles that are required to cover them. Click on the graphic to see an enlarged view.

Ultimately, the right sensor size for you depends on your photographic needs and preferences. If you prioritise image quality, low-light performance, and shallow depth of field, a full-frame or medium format camera might be worth the investment. On the other hand, if portability, affordability and versatility are more important, an APS-C or Micro Four Thirds camera could be the better choice.

As you can see in the illustration, there are a lot of variables to play with. The distance between the source and patch can affect the hard edges as well as the angle of light on the subject. Moving the subject back and forth, the angle of incidence changes slightly, giving you a variety of effects. For the metal image, I also had to rotate the surface so light would just barely skim across the top. Note the highlights are essentially blown out – these surfaces face the side-firing light more directly.

A ‘full-frame’ sensor matches the size of a 35mm film frame at 24x36mm, sometimes dropping to around 23.9x35.9mm. There are also smaller sensors like APS-C, Four Thirds, 1-inch and even smaller formats. APS-C sensors are named after the short-lived Advanced Photo System Classic film format, which measured 25.1x16.7mm, however, APS-C sensors typically come in at about 23.5x15.6mm.

Medium format sensors are named after medium format or 120 film, with typical film frames of 6x4.5cm, 6x6cm and 6x7cm. Interestingly, 35mm film was often called ‘small format’ to distinguish it from medium format film.

Consequently, cameras with smaller sensors, like APS-C or Micro Four Thirds, are often more appealing to photographers seeking a compact and lightweight system. They can produce great image quality in a more portable package, making them ideal for travel, street photography, or any situation where space and weight are key considerations.

However, the number of pixels isn’t the only factor in image quality; sensor size plays a crucial role as well. A larger sensor with fewer, but larger, pixels can capture more light, resulting in stronger image signals and, consequently, better image quality. This is why full-frame sensors, despite sometimes having a similar number of pixels as smaller sensors, often produce superior images with less noise and greater dynamic range in low light.

This graphic shows the relative sizes of full-frame, APS-C with 1.5 crop, APS-C with 1.6x crop and Four Thirds type sensors. Click on the graphic to see an enlarged view.

This small toy dragon was given drama with the same lighting treatment. In this case, the trailing edges are cool and highlighted, while the front is glowing warmly. I moved the model further from the dark patch to reduce the edge lighting, which meant I had to make use of the aperture flags to control spill again. In the setup illustration, the offending stray light is shown along the green line, so the flag on camera left was brought inside the field of view, then cropped out. I also had to move the camera back a little and zoom in.

Finally, this headset shows a combination of opaque and translucent surfaces. The metal frame has beautiful, hard highlights, while the plastic ear and mouth pieces almost glow, pulling the light further around than the contrasting opaque edges. This combination of opaque and translucent edges really shows off what you can do with dark field lighting, showing just enough detail that you can recognize the subject without giving it all away.

Dark field photography lighting is a great way to build drama and moodiness, even in mundane subjects. But it can also give a lot of information about small details textures and edges. Combining these characteristics yields some fantastic creative results. The keys to vastly different looks lies in experimenting with the relationships of off-camera elements in your setup, as well as combining with other lighting techniques. Rotate your subject, look for unique angles. The headset and metal images are suspended from black cord and wire, for example. Pay careful attention to highlights, and add or take away gobo pieces to shape your surface reflections. But most of all, get in there and tinker!

Larger sensors are often touted for their ability to produce shallower depth of field, which helps create those creamy, blurred backgrounds that make subjects pop. However, this is actually more about the relationship between sensor size, focal length and aperture. To achieve the same framing with a full-frame camera and an APS-C camera, you need to use different focal lengths. Because depth of field decreases as focal length increases, changing the focal length affects the depth of field.

Medium format, full-frame, APS-C and Four Thirds are commonly used camera sensor sizes. This post explains their significance and the impact of sensor size on photography.

In digital cameras, film has been replaced by sensors and there are a variety of sizes in common use. By sensor size, I mean the physical size of the chip, not its pixel count or resolution.

Although camera sensors are rectangular, lenses produce a circular image. This must completely cover the sensor so there are no blank areas in the image.

Micro Four Thirds cameras have a 2x crop factor so they double the effective focal length of lenses. Consequently, a 14-42mm lens on a Micro Four Thirds camera behaves like a 28-84mm lens on a full-frame camera. This is especially interesting with longer lenses, as a 300mm lens effectively becomes a 600mm lens.

There are also sensors that are larger than full-frame format chips. Fujifilm, for instance, has the GFX line of medium-format cameras. These cameras, such as the Fujifilm GFX100S II, have a sensor that measures 43.8 x 32.9mm, close to 1.7x the size of a full-frame (35mm) sensor.

A digital camera’s sensor is packed with millions of tiny light receptors known as pixels. When light hits the sensor, each pixel generates a signal based on the light’s intensity, which is then converted into a digital image. The number of pixels on a sensor determines the resolution of the images it produces, with more pixels generally allowing for larger prints and more detailed images.

Each sensor size comes with its own set of advantages and disadvantages, so it’s important to consider what matters most to you in your photography. Whether you’re shooting sweeping landscapes, intimate portraits, or fast-paced action, understanding sensor size will help you make the best choice for your needs.

Angela is the founder of SheClicks, a community for female photographers. She started reviewing cameras and photographic kit in early 2004 and since then she’s been Amateur Photographer’s Technical Editor and Head of Testing for Future Publishing’s extensive photography portfolio (Digital Camera, Professional Photography, NPhoto, PhotoPlus, Photography Week, Practical Photoshop, Digital Camera World and TechRadar). She now primarily writes reviews for SheClicks but does freelance work for other publications.

Now check out the vacuum tube. It was shot in nearly the same setup as the metal box, but I had to adjust the aperture flags a bit to prevent spill into the lens, which would cause flare. This shot was a little more difficult to set up because I wanted the dark field light to show off the edges of the glass, while the coil and other elements were lit by a warm fill. This picture demonstrates another challenge with shooting glass: stray reflections. Since this particular glass is laying down, I had to be careful to cover up any reflective or light surfaces from above that I didn’t want to show up. The side baffles in the illustration are used for this purpose, as well as a top ‘cap’ on the table-top stage.

These are both Micro Four Thirds cameras and have the same size sensor. Using a small sensor allows camera manfuacturers to make smaller cameras if they want.

Thanks to their 2x focal length magnification and very acceptable image quality, OM Systems Micro Four Thirds cameras have proved very popular with wildlife photographers who need long telephoto lenses.

Having a larger sensor also allows more pixels to be squeezed onto a sensor without image quality being over-compromised. The medium format Fujifilm GFX100S II and GFX100 II, for example, have a resolution of 102MP.

Sensor size also affects the lenses you need and how they behave. Larger sensors require lenses that produce larger image circles, which usually means bigger lenses. If you use a full-frame lens on an APS-C sensor camera, the lens’s image circle exceeds far beyond the sensor size and the image is captured from just a small section within the circle. This results in what appears to be a cropped image and the effect is often called the crop factor or focal length magnification factor. It makes the lens appear as if it has a longer focal length on a smaller sensor. The smaller the sensor, the greater the crop factor.

For example, Fujifilm, Nikon, and Sony APS-C cameras have a crop factor of 1.5x, so an 18-55mm lens gives a field of view equivalent to a 27-82.5mm lens on a full-frame model. Meanwhile, Canon’s APS-C cameras have a crop factor of about 1.6x, making the same lens appear like a 28.8-88mm lens on a full-frame camera.

The buzz around full-frame and medium format cameras stems largely from the size of the photosites (commonly known as pixels) on their larger sensors. Bigger pixels can capture more light, producing a stronger image signal. This stronger signal means less need for amplification, resulting in images with less noise, or grain, particularly in low-light situations. This is why cameras with larger sensors often offer higher ISO settings and better performance in challenging lighting conditions.

Light from your source will spill over the edges of your patch and “graze” the surface of your subject. By controlling the amount of spill, you can control how much light wraps around your subject. You can do this by changing the size of your light source, or more simply by repositioning the patch, thus changing the relationship between the sizes of the light and the patch. Check out the illustration if you’ve not tried this setup before.

The origins of names like Four Thirds, 1-inch, and 2/3-inch are rooted in the era of video camera tubes, which is why their naming conventions can seem a bit obscure. However, these names have stuck, and they represent a range of sensor sizes: Four Thirds sensors are usually around 17.3x13mm in size, 1-inch sensors are about 13.2x8.8mm and 2/3-inch sensors typically measure 8.6x6.6mm. As you might guess, Four Thirds sensors are found in modern Micro Four Thirds cameras.

I first used dark field imaging in microscopy, examining the surface of metals for technical characterization. In this tiny world, dark field imaging lets you see surface textures that can otherwise be hidden using standard bright field, or direct lighting. Photographers can use the same idea to bring out texture or enhance detail. When combined with more traditional lighting, you can get some startling effects.

This image was photographed on a full-frame camera at a focal length of 70mm. The trees appear closer, or larger, in the frame than in the image shot at 35mm.

When film photography reigned supreme, 35mm film was the go-to format. You’d crack open a film canister, carefully load the film into your camera and be ready to shoot. Whether using a simple point-and-shoot or a professional-level SLR, the film size remained the same.

Superzoom and bridge cameras typically have very mall sensors and this enables them to achieve vast effective focal length ranges and long zooms on compact bodies.

The ‘A’ image is shot with a combination of dark field and soft front fill lighting. The ‘B’ image is shot only with dark field lighting. You can see details on the surface that are invisible in the more traditional lighting shot. These details are surface defects that are the same color as the surrounding metal, but have a slightly different height (tiny scratches and dings). You can also see the different highlight positions in the two shots. Nothing changed between the frames except turning off the front fill. In post processing, I reduced the saturation so the effect is more readily visible, but only minor sharpening and exposure control was used.

This grazing light (blue in the illustration) is what you can use to your advantage for bringing out textures, especially in otherwise flat (not necessarily smooth) surfaces. To get this specific effect, the area you photograph must be relatively flat in the field of view. Imagine a basketball: it’s round all over, but if you zoom in with a macro lens the surface can look flat compared to the raised textures from the little bumps. Check out the two images of a metal surface.

Additionally, I dropped a strip of orange construction paper along camera right, just below the glass – there is a warm highlight along that lower edge of the subject. This provides some depth cues for the viewer. Post processing again was done simply by exposure control and a small amount of sharpening. You can see that I didn’t get the glass quite clean enough – this is a hazard of dark field imaging!

From left to right we have cameras with a Four Thirds type, APS-C format and full-frame sensor. Although the Micro Four Thirds Panasonic Lumix G9 II has the smallest sensor,  it is as similar size to the full-frame Nikon Z7 II.