In order to make a picture such that 15 cm tall kingfisher just fits in the camera's longest dimension, you will need - besides patience and some luck - the right equipment:
a camera with a full frame sensor and a 1200 mm telephoto lens
a camera with an aps-C sensor and an 800 mm telephoto lens
a micro-43 camera and a 600 mm telephoto lens
Cambridge in Colour offers several calculation modules which help you answering questions like:
Which focal point do I need at a given camera and distance to a subject, to fit that subject in the camera's longest dimension?
How large is the depth of field at a given camera, lens, aperture and focussing distance?
At which aperture setting starts sharpness to diminish because of diffraction?
Calculating Depth of Field
Depth of field is, in short, the area which is sharp in the photo. Depth of field is approximately dependent on the sensor size ("camera type"), the focal length, the aperture and the distance on which is focused. At Cambridge in Colour there's an additional, extended depth of field calculation, where also the size of the print, the viewing distance and the quality of your eyes are included in the calculation, for an accurate calculation of depth.
Diffraction (circle of confusion)
Initially, your photos become sharper if you choose a smaller aperture. But at some point, the aperture is so small that light scattering (diffraction) occurs, making the photo less sharp again. Diffraction depends on the sensor size ("camera type"), the focal length, the aperture, the focus distance, the size of the print, the viewing distance and the quality of your eyes. Use this calculator to calculate the aperture where diffraction begins to dominate.
The smaller the sensor, the less you can / have stop down before diffraction occurs and the image becomes less sharp ("softer"). With many compact cameras, you cannot stop further than 5.6 or 8 for this reason, while with SLR cameras with a full-frame sensor, the optimum sharpness ("sweet spot") is actually reached at these apertures. SLR lenses can often be set to aperture 22, but if you do not want to lose too much sharpness, you better remain under aperture 11 with an SLR camera with full-frame sensor.
The hyperfocal distance is the smallest distance at which a lens can be set, so that subjects at infinity are still sharp. It is the focus distance with the greatest depth of field. Calculate the hyperfocal distance yourself based on the desired print size, viewing distance and sensor size ("camera type").
Hyperfocal distance in practice
If I want to use a 16 mm lens (converted to full-frame) to take a night shot that is sharp from front to - say one meter – back, choose:
a full-frame caera with a 16 mm lens on aperture 11
a camera with aps-C sensor and a 10 mm on aperture 5.6
a micro-43 camera with an 8 mm lens on aperture 4.5
These 3 different combinations will give the same result.
At Cambridge in Colour you can find a module to calculate the focal length you will need for capturing a subject, such as a kingfisher, full screen, based on the size of the subject, the sensor size ("camera type") and the distance to the subject.
Magnification in practice at macrophotography
If you want to take a macro recording with a 50 mm lens with a magnification of 1 (the image on the sensor is as large as in reality), you need to choose a distance of 20 cm regardless of the type of camera (or sensor size).
Do you want to calculate what magnification you can achieve with macro photography? The magnification only depends on the distance to the subject and the focal length of the lens.
Macrophotography: Depth of field
Depth of field is an essential parameter for successful recordings with macro-recordings. Use this calculator for calculating the depth of field of your macro recordings.
Macrophotography: Diffraction limit calculator
At some point, further diaphragming is of no more use, because the increase in depth of field is offset by diffraction. With the Macro diffraction limit calculator you know when this is the case.
Panorama photography: Field of View (FOV) calculation
The calcaulation of the Field of View is a handy tool for panaoram photography: how many shots do I need take with a particular lens to make a 360 degree panorama? Here is a link to a Dutch website where you can find an angle calculator at the bottom of the page.
With Camera Review Stuff I hope to make a modest contribution to the pleasure that you get from photography. By testing cameras and lenses in the same way, evluating the results and weighing up the pros and cons, I hope to help you find the right camera or lens.