To tele-convert or not to tele-convert.
Who doesn’t want more reach? In an ideal world we’d all be shooting with a 600mm f4 but is 1.3x more light really worth the ~$10,000 difference between that and a 200-600mm f6.3? What happens when your subject is even further away? My Sony a7RIV has 61mp and 24mp when shooting in crop mode. The advantage of crop mode is an additional 1.5x reach, now your 600mm turns into a 900mm. However, when adding 1.5 reach you also lose a stop and half of light, crop mode is 900mm f9.45.
When you multiply the aperture by 1.5, the resulting aperture value will be 1.5 times larger than the original value. This means that the diameter of the aperture will increase by a factor of √1.5 (approximately 1.22).
For example, if the original aperture value was f/2.8, multiplying it by 1.5 would give you an aperture value of f/4.2. This means that the diameter of the aperture would increase by a factor of √1.5, which is approximately 1.22 times larger than the original diameter.
If you multiply an aperture of f/6.3 by 1.5, the resulting aperture value would be f/9.45. This means that the diameter of the aperture would increase by a factor of approximately 1.22, which would result in a smaller aperture opening.
A smaller aperture opening (larger f-number) would result in a deeper depth of field, which can be useful for landscape photography or other situations where you want most of the scene to be in focus. However, it would also result in less light entering the camera, which may require a longer exposure time or higher ISO setting to compensate for the decrease in light.
What would happen if you add a tele-converter to this situation? If you add a 1.4x tele-converter you multiply an aperture of f/9.45 by 1.4, the resulting aperture value would be approximately f/13.23. This means that the diameter of the aperture would increase by a factor of approximately 1.18, which would result in a smaller aperture opening. BUT! you now have a 1260mm f13.23 for ~$3000! So why isn’t everyone doing it?
Teleconverter, also known as a tele-extender, is an optical accessory that is used to increase the effective focal length of a lens. It is essentially a magnifying lens that is placed between the camera body and the lens, which increases the magnification of the image. Here are some advantages and disadvantages of using a teleconverter:
Advantages:
Increased Magnification: A teleconverter can increase the effective focal length of a lens, which means that the subject will appear closer and larger in the frame. This can be useful for wildlife, sports, or any other type of photography where you need to get closer to the subject.
Cost-effective: Teleconverters are generally less expensive than buying a longer lens with the same focal length. This makes them an affordable option for photographers who want to increase the magnification of their existing lenses.
Lightweight: Teleconverters are small and lightweight, which makes them easy to carry in a camera bag. They also do not add much weight to the camera setup, making it easier to handhold the camera.
Disadvantages:
Image Quality: While teleconverters can increase the magnification of the image, they can also reduce image quality by introducing chromatic aberration, distortion, and softening of the image. The effect can be more pronounced with lower quality teleconverters.
Light Loss: Teleconverters reduce the amount of light that reaches the camera's sensor, which can result in slower shutter speeds, higher ISO settings, or the need for a tripod.
Autofocus Issues: Some teleconverters can cause autofocus to become slower, less accurate, or stop working altogether. This can be particularly problematic in low light conditions.
Compatibility: Teleconverters may not be compatible with all lenses or camera bodies, and using one that is not compatible can cause damage to the lens or camera.
Overall, teleconverters can be a useful tool for increasing the magnification of a lens, but it is important to weigh the advantages and disadvantages before deciding to use one. The image quality and compatibility issues should be considered before making the investment in a teleconverter.
ƒ/6.3 1/1250 600mm ISO125
900mm f/9.45 1/1250 iso 125
