How do I choose a camera for macro photography without considering special lens?

Question

For macro photography, how do I choose between a compact camera or a mirrorless interchangeable-lens camera (without considering a lens)?

What indicator(s) should I look for when making the choice?

Answer 1

As far as hardware goes all photography is primarily about the lens. And Macro photography is even more about the lens than almost any other type of general photography. You really can't choose a camera for macro photography without considering the lens. To successfully do Macro photography a camera needs to include a lens that demonstrates certain characteristics.

These are things you need to consider when looking for a camera/lens combination to do Macro photography:

• Minimum Focus Distance (MFD) As measured from the image plane (the plane occupied by the sensor or film), what is the closest an object can be that is within the lens' capability of focusing? The closer the MFD, the larger you can make the same objects appear in your photos.
• Maximum Magnification (MM) This is a combination of focal length and MFD. It is expressed either as a ratio (1:1), a percentage (100%), or a decimal value (1.00). A lens that projects an image on the sensor that is one half the actual size of the object pictured has an MM that can be expressed as 1:2, 50%, or 0.50. Most photographers consider true macro lenses to be capable of a 1:1 reproduction ratio, while 1:2 is generally considered the minimum MM needed for macro work. Some manufacturers will claim telephoto lenses with an MM of around 0.30 are also macro lenses.
• Working Distance This is related to MFD, but is measured from the front end of the lens. It is the amount of space between the front of the lens and your subject. If a 50mm lens has an MFD of 9.1" and the front of the lens is 5.5" in front of the image plane, that leaves a working distance of just over 3.5" between the front of the lens and the subject. A longer focal length usually allows a longer working distance at MM for doing macro work with things like bugs or insects without getting too close and driving them away. A typical 180mm macro lens might have about 9-10 inches of working distance at 1:1 magnification. More working distance also makes it easier to avoid shading the light falling on the subject with the lens.
• Sensor resolution/size Why does sensor size matter? Because the size of the sensor determines how much the image projected onto that sensor by the lens will be magnified when the photo is displayed at a specific size. A full frame size sensor is about 1/4.25 times the size of a 4" x 6" print, so the image projected by the lens onto the sensor is magnified by a factor of 4.25. An APS-C sensor is magnified by about 6.75 times. The micro 4/3 format is magnified about 8.8 times to create a 4" x 5.3" print or by a factor of 9.9 to create a 4" x 6" print with part of the top/bottom cropped off, and so on. Why does resolution matter? Because the number of pixels per inch after magnification contributes to the quality of the print. This would lead one to believe that a smaller sensor would be advantageous for macro photography since a smaller image projected by the lens is subject to more magnification for a specific viewing size. But as with many aspects of physics, there is no free lunch. The smaller sensor size also reduces the sensitivity to light, which is another important aspect of macro photography.
• Maximum Aperture The aperture of the lens determines how much light makes it through the lens and falls on the sensor. In the digital realm more light means more signal. In general the more light/signal your sensor captures the lower amounts of visible noise the image will show. Since aperture is usually expressed as an f-number and f-numbers are fractions, the smaller the f-number is the larger the aperture is and the more light can reach the sensor. A 50mm f/2 lens allows twice as much light through as a 50mm f/2.8 lens does. A 50mm f/1.4 lens allows twice as much light as the f/2 lens and four times as much as the f/2.8 lens. Although narrower apertures are often used when shooting macro to increase the very shallow depth of field, the wide aperture is helpful for such critical focusing as is required by the close shooting distances. This is true whether using auto focus or manually focusing through the viewfinder. Even when focusing using Live View a wider aperture will allow a brighter, less noisy image on the camera's rear LCD. One effect close focusing has is to alter the effective focal length of the lens which in turn affects the actual f-number. As the effective focal length gets longer the same sized opening in the diaphragm results in a higher f-number, and the image reaching the camera's light box gets darker. This is further compounded because the subject is so small and is thus reflecting less light than a larger object at a greater distance from the lens occupying the same angle of view would under the same ambient lighting conditions.

Answer 2

Well, you cannot completely dissociate one from the other for the compact case because the lens is attached.

• For a mirrorless camera, they are all capable of using macro lenses but if you get one which is compatible with the Canon EF lens mount, you can use their unique MP-E 65mm lens which gives 5X magnification. This is an extreme macro lens which has no equivalent in other brands.
• For a compact camera, manufacturers specify the minimum focus-distance. This is relative to the front of the lens, so you cannot compare with lenses for mirrorless (or DSLRs) which specify focus-distance from the sensor-plane.
• Canon (yes, again) makes the only cameras to focus at 0cm from the lens, meaning you can focus on dust or put something right against your lens. The main problem here is illumination, so this works mostly for transluscent objects you can light through.
• Otherwise Fuji and Canon also make lenses which focus down to 1cm from the lens. You will not get as much magnification is with a true macro lens as you would on a mirrorless or DSLR but you can get pretty close. Again, getting light onto your subject is the trickiest part given the lens is so close.