Sigma 150-500 mm os + 2x tc.

Hallow everybody, I have a sigma 150-500 mm os,if i use a 2x tc with this lens what will be the problem and why, as i hear that this combination not works well.
Can any one explain why?

With regards,

Abhirup D.Gupta

Hi

I used to have this as my mainstay combo a few years ago (Still have it, though hardly use it) and here are a few of my observations of this combo.

- Auto focus does not work on this combo (especially with a 40D, 400D body combo)
- at the outer end of the lens (500mm) the image quality tends to drop. Add a TC to this combo and i always landed with soft images even with plenty of light
- f6.3 is the lowest end of the aperture. with a 2X (two stop loss) the effective aperture is almost double and you will need a lot of light for sharp images
- Even on full frame sensors the combo gets you into the diffraction zone
- at times i felt that a cropped image without the 2X was even better than the uncropped ones with the 2X
- most of my images with this combo had the contrast as the causalty - meaning the blacks were badly hit and had to be recovered in PP

hope this helps

regards
Rajan

Thank you very much Rajan sir for your kind reply.Can i use this 2x tc with tamron 70-300 mm f2.8 VC,will it work better?

With regards,

Abhirup D.Gupta

My apologies. Honesty have no idea about the Tamron. Maybe others who have used this may chip in with their views.

regards
Rajan

Agree with Rajan. The 50-500 lens is not meant to be used with converters. Please remember that a converter will also magnify any faults in the lens. One should use converters only with lenses of very good optical quality. Else, the quality becomes poor.

I am not sure if Tamron has a 70-300 with 2.8. I know it has one with f4-5.6 aperture. Or did you mean to say 70-200 f2.8?

No idea whether a TC will fit the Tamron 70-300 f4-5.6. Even if it fits, don't hope that you will get good quality images. When you slap at 2x TC on a lens which is f5.6 at 300mm then the combination becomes 600mm at f11. How many times can you click at f11 with a good shutter speed in good light? Normally, to get a better sharpness, we need to stop down close to one stop. However, you are already at f11 aperture and most of the digital cameras today will produce soft images due to diffraction.

Also, with increased pixel density in our digital cameras, any shake and aberrations of the lenses become exaggerated and became painfully evident at 100% viewing. That means any cropping of image would only further highlight the faults. And when we critique such images, people at times feel that we are minutely examining things. :(

Thank you very much sir for your information.

With regards,

Abhirup D.Gupta