RainbowImaging Canon lens to Sony E Mount adapter

[Joel Corral]

So i purchased the RainbowImaging Canon lens to Sony E Mount adapter. obviously there is no iris control now. I slapped on a sigma 70mm - 300mm f4-5.6. Since there is no iris control what is the lens set to f4? does this mean i can zoom to 300mm @ f4? i did small test, i personally couldn't tell if there was loss of light.

i am still very new to shooting DSLR video and need to wrap my head around all these lenses and adapters!

JC

[Joel Corral]

PLEASE correct me if i am wrong: I need to understand this! :)

So for automatic diaphragm lens, the aperture is wide open until the moment of exposure. But that doesn't mean that if i zoom in to 300mm the aperture setting will stay at f4, correct? The lens will have limitations within the physical design that will natively create the aperture, in this case of f5.6, correct? so at full telephoto range 300mm the lens' will be set to f5.6 even though the aperture blades are fully open? correct?

I know there is someone here to help me on this one!

JC

[Steven Digges]

That is correct Joel,

At 300mm you are loosing light because of the lens design. The aperture blades are still in the same place at F4 at full wide.

If you look at a constant aperture zoom at f2.8 for example they are big and heavy. There is a correlation between focal length and transmitted light. The higher the magnification the more good glass you need to transmit it. They are expensive because of the lens elements required to achieve it.

Sports lenses are another good example. There "size" is deceving to many people, they look like super zooms but often they are not. I had a Nikon 600mm f4 lens when I was doing a lot of sports. It was probably two feet long and had a front lens element almost six inches across. That is what it takes to get f4 at just 600mm.

Steve

[Joel Corral]

Thank You! been doing video since 2002 with fixed lenses but this ea50 is a whole new world for me! love learning!

[Steven Digges]

You can get a Metabones Mark III adapter to restore lens functionality for $400.00. You shoot on a fixed stage so you probably don't need the $600.00 speed booster? What aperture are you normally shooting at on that stage?

Steve

[Joel Corral]

For my stage shoot i am shooting at f5.6 with ISO2500 with tweaks made to PP5. i am only using ambient house lighting now as there has been restrictions made to my shooting environment that have disallowed me to use my mole richardson lighting kits. This is why i have a sudden urge to find a faster lens! so i am educating myself and need to fully understand of how these lenses work. Right now i am anticipating the release of SELP18105G 18mm-105mm f/4 Mid-Range Zoom Lens. Hopefully the auto focus sufficient enough.

My plan is to sell one of the ea50 stock lenses i have and purchase 2 of the SELP18105G's....

[Steven Digges]

I would expect the AF of the SELP18105G to be at leat as goog and probably better than the 18-200mm.

I see the 18-200mm on e-bay all the time for about 800 / 900 bucks.

Steve