Adding 1.4x and 2x on 300 f2.8?

[bsmith6280]

Can this be done? Or can you add two 1.4x's together on this lens?

[Jon]

Yes, either can be done. IIRC, you need to be careful which order you stack the TCs, since they only fit one way. And your IQ will go down the tubes.

[Ronald S. Jr.]

The 300 will look very nice with either TC. But, as Jon said, stack them, and your IQ level comes crashing down. Just use the 2x for 600mm.

[bsmith6280]

thanks, Ronald and Jon. Much appreciated. I only asked because I saw a photographer at pbase stack both on a 400mm f2.8 to get some pretty cool moon shots.

[12345Michael54321]

In addition to taking a real hit in image quality, stacking them would cost you 3-stops. That takes the lens down to a maximum aperture of f/8. Some cameras won't autofocus under those conditions, and others will autofocus, but you're pushing the envelope so their AF performance may be iffy.

[12345Michael54321]

I didn't see the mention of moon shots. Obviously, autofocus isn't terribly important if you're photographing the moon. It's usually somewhere out around infinity focus, and almost never zooms toward you in such a way that predictive autofocus is of benefit. (It also tends to be a rather high contrast object, which makes accurate focusing relatively easy.)

[Jon]

If yuo need the magnification, I guess it's worth it.