Image quality

[dicklaxt]

I know some will think this a stupid question but this darn "Photography Stuff" gets me to asking myself questions I can't answer so "Curious George" rides again.

This is the scenario:

If you set the Zoom on the lens to 121mm
when used with a 1.4 Teleconverter that would equal approximately 170mm,now using a different Zoom lens with out the Teleconverter and you set that second lens to 170mm,,,,,,,,would the Image Quality be the same from both or would one be better than the other?

Don't ask me why I would do something like this as I said its curiosity.

dick

[directshooter]

It just depends on certain factors , most of the time convertors need to be compensated for? also some have optics some dont?

Generally speaking a convertor documented image will be slightly less quality but in saying that on a canon T90 camera with certain lenses when a convertor is used ' no compensation is required, so quality is the same ' ?

Si.

[jonrayner]

I cannot remember where I have heard it, but my understanding is that when using a TC, you will lose some image quality.

[coffee]

I don't think the average Joe Photographer will be able to tell the quality drop of a TC most of the time, but I've seen no side by side test. Maybe do a search on TC quality. But your problem with the comparison in your example is that you are using two different lenses that may not be the same quality, so it would be very hard to make a good comparison. If you are going to do a controlled test maybe just use one lens with and without the TC and adjust the focal length accordingly.

[jonrayner]

I don't think the average Joe Photographer will be able to tell the quality drop of a TC most of the time, but I've seen no side by side test. Maybe do a search on TC quality. But your problem with the comparison in your example is that you are using two different lenses that may not be the same quality, so it would be very hard to make a good comparison. If you are going to do a controlled test maybe just use one lens with and without the TC and adjust the focal length accordingly.

Good point!

[jerryph]

There is a small drop in quality, even on the best TCs... but more importantly, there is a big drop in light. Adding a 1.4 drops you 1 stop of light, a 1.7 about 1.5 stops and a 2X drops you 2 stops of light. Meaning... if your lens was an F/4 at 200mm, slap on a 2X and it becomes a 400mm... but the best aperture you will be able to do is a F/8... which means that this lens is pretty much useless in all but the brightest of days. Also, some lens/camera/TC combos cannot meter above F/5.6, this makes the entire exposure affair totally manual.