21

If you shine a torch (flashlight) on a wall and walk forward, the circle of light gets smaller, but brighter at the same time. The principal of the speed booster is the same. A lens designed for 35mm projects an circle of light at least 43mm in diameter onto the sensor. The sensor in an APS-C format camera has a 28mm diagonal. The "speed booster" ...


12

Just FYI, a new EF 50mm f/1.8 STM or a new EF-S 24mm f/2.8 STM is about US$130 (at the time of this writing). That's less than half the price of a Metabones Speed Booster, so your assumption that you can't afford a fast lens isn't exactly correct, if you're willing to give up zoom capability and go with a prime lens. The speedboosters are wide angle ...


9

LensRentals.com had quite a lengthy article on this subject a couple of days ago. Basically it works by focusing the amount of light going through the lens on to a smaller area, optimized for the smaller sensors of mirrorless cameras. This increases the light intensity of the image being captured, giving a "1-stop aperture increase". I'll just link to the ...


6

Theoretically, optically, it would work (for low-quality values of "work"). Yes, the focal reducer would give an extra stop of light. But because the 2x teleconverter is responsible for 2 stops of light loss, you'd still net 1 stop of light loss. Aside from the optics math, there are some real practical problems with this approach. Depending on exactly ...


4

The ratio f/2.8 means the diameter of the entrance pupil is equal to the focal length divided by 2.8. The key thing to note about the above is that the entrance pupil is the image of the aperture stop as seen through the front of the lens, the ratio does not depend on the physical size of the aperture itself. A rear-mounted 2x teleconverter, such as you ...


3

A speed booster does not change your sensor. Not in any shape, way, or form. It changes the size of the image circle projected by your lens, making it smaller. The usefulness of a speed booster is to combine lenses that cast large image circles, such as lenses made to be used on full frame cameras, with camera bodies that have smaller sensors. By reducing ...


3

You speak of two different factors. The 2x crop factor equivalence of 4/3 sensors is based on the sensor size. The 4/3 camera sensor has a crop factor of 2, meaning it has a diagonal 1/2 the dimension of a full frame camera, so the smaller sensor "crops" the field of view seen to be only 1/2 of the field of view (1/2 of the diagonal dimension). The lens is ...


3

A focal reducer doesn't follow the conventional wisdom that a teleconverter reduces image quality because it works in a completely opposite way from a teleconverter. Are you familiar with why "crop factor" exists? A full frame ("FF35") lens projects a circle about 43mm in diameter into a camera. A FF35 sensor is 36x24mm and so records most of that circle. ...


3

Metabones Ultra 0.71x EF to MFT is for APS-C This is sort of incorrect. Both the Metabones XL 0.64x EF to MFT and the Metabones Ultra 0.71x EF to MFT are primarily intended to be used with full frame EF lenses. If one reads the official Metabones product page for the Ultra 0.71x EF to MFT, one sees that there are several caveats to using an APS-C lens with ...


3

The nice thing about teleconverters is that they extend the effective focal length of the lens. That makes it easy to design them with enough thickness in front of the camera's mounting flange to fit all of the needed optics inside. In the case of speed boosters, though, we are effectively reducing the lens' focal length, which means the lens elements in ...


2

In theory, it should "work". But the light you "gain" by using the 0.71X focal reducer will be more than offset by the light you "lose" from using the 2X teleconverter. Likewise, the focal length you "gain" by using the 2X TC will be partially offset by the focal length you "lose" by using the 0.71X focal reducer. If your 50mm lens has a maximum aperture ...


2

Does your FD-to-EF adapter have a glass element? If so, then yes, you can do it, but the results will be fairly poor, IMO. If your FD-to-EF adapter doesn't have a glass element, then your proposed combination will cause you to not be able to focus to infinity. This is because the flange focal distance of the FD mount is 42 mm is less than the flange ...


2

Aspect ratio doesn't really matter for this particular purpose, because the corners of whatever rectangle you choose need to be covered by the image circle — so, the diameter needs to at least meet the a corner-to-corner distance. If one were to crop a 36×24mm frame to 4:3, that'd be 32x24mm, and a smaller diagonal. But all of the real-world lenses are ...


2

Michael C gave you a really nice answer about the speed booster. But I wan to address the other question. Can anyone give any advice? Well, stop reading things about the "disadvantages" of a cropped sensor because they are bothering you for "some reason", but it does not look for any particular reason. Take your camera and shot. Enjoy taking photos, ...


2

It's not possible to use a focal reducer on a crop sensor camera with lenses whose flange focal distance is close to the native FFD of the camera because there is no space to put the focal reducer optics. In addition to reducing the size of the imaging circle, focal reducers also decrease the FFD. So even if you could fit the optics in somewhere, the lens ...


1

I own a Canon Rebel T7i ... Is it a good idea to purchase a speed booster ...? There is no focal reducer available for your camera. ... should I just purchase a 35mm prime at f/1.4? Not all 35/1.4 lenses are the same. What do you need it to do? If you were to switch to a crop-sensor mirrorless system, focal reducers could expand the usefulness of ...


1

Crop factor --- The full frame 35mm film camera introduced in 1923 by Leitz Manufacturing and named Leica, became so popular that zillions of cameras using this format were marketed. The format dimensions or frame size measures 24mm height by 36mm long. The height to length ratio is 3:2, and this size enlargers exactly to film a 4x6 or 8x12 inch piece of ...


1

You probably can do it, but stacking adapters increases the possibility of manufacturing inaccuracy causing focus issues (either focusing past infinity, if the adapter combination's too thin, or not focusing to infinity if the combination's too thick. The main thing to keep in mind, however, is that you will lose all the electronic communication with a ...


1

There does not appear to be a focal reducer to adapt lenses to EF-S bodies. The problem is there is no room between the lens and body to put additional optics. As @inkista states, you are better off using a flash or purchasing a fast, inexpensive lens, such as a nifty fifty.


1

I'm curious if it's worth using a focal reducer on a Nikon AF 300mm f4 on my Sony a6000 is worth it, or is it better spent saving the money to get a FF body to "match" the lens? Why can't both be true? You linked to Roger Cicala's blog post about the Metabones at LensRentals.com – why not go ahead and rent one, and a FF body as well, to test them out? Then ...


1

My question here is, what is the conventional wisdom stated above Looking at the post you referenced, author Matt Grum describes the conventional wisdom: However, the statement "when you add elements to a lens, you make the image worse" is not true absolutely... He goes on to explain that it is indeed possible to add elements that improve lens performance....


1

From this PC Mag review, it looks like the center isn't too badly impacted, but the fall off near the edges of the image become pretty severe. I don't have any direct experience, but the general review seemed pretty positive even if there is some barrel distortion. It seems like unless you need the reduction in the crop factor, you are better off to just ...


1

Yes, there is. Metabones offers the SpeedBooster.


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