I don't recall where this was much discussed, but wherever, it was
between people who know far more than I about the finer things in
photography.
The general consensus was that most teleconverters do degrade the image
somewhat, 2x converters being quite a bit worse than 1.4 converters, and
that one is better off to shoot without one and crop the image as part
of processing it.
This was prior to the vast improvements we've seen in AI driven image
resizing, so my own opinion, which is probably not worth much, is to
forget about the 2x converter and if you have enough pixels to crop, do
it, and if you have to use an AI resizing tool to give you enough pixels
to crop with, resize and then crop.
Obviously this gives some limitations. For example, with the 2x
converter you will bring a very distant subject close enough that
resizing will give a more usable image, and this is a consideration that
must be accounted for.
Matched multipliers seem to be the exception to this as do the higher
end units. I have the Rear Converter A 1.4X-L which I use from time to
time with my A*600/5.6 and it seems fine. It is well matched to the lens
though.
When I went on my Fuji buying spree a couple of years back I purchased
their 1.4 teleconverter to stretch out my 50-140/2.8 and it also seems
quite good, but when I was researching it I was told to definitely stay
away from their 2x converter. Apparently it isn't up to the red badge
Fuji lenses and degrades them quite a bit.
HTH
bill
On 6/26/2025 1:39 PM, Larry Colen wrote:
After Paul's comment about using the 2x on the 150-450 I looked into
them a bit.
It seems as if the Pentax 2x will crop on FF, but that Tamron has one
that won't.
Also, after looking at some posts by folks who pixel peep, that when
it comes to fine detail, the teleconverter doesn't actually gain you
anything in detail in the final image over cropping. In short, when
the sensor is outresolving the lens, a 2x TC will give you four times
as many pixels, but each pixel is only 1/4 as good.
It seems to me, that if you are shooting professionally, where post
processing time is of the essence, then if the detail in the final
image is about the same, then the TC is definitely worth it,
particularly if you aren't shooting wide open anyways, and the loss of
a stop or two doesn't matter.
My only real experience with this was many years ago, I did some
tests, photographing the moon, and the final images, cropped to the
size of the moon and processed to the same number of pixels, if
anything the TC images were degraded over the cropped images. Back in
the days of film, where film, particularly tri-X, didn't out resolve
the lens, then the TCs would make a significant improvement.
So, do TCs help? If so when? Thoughts? Experience?
If so, which ones do the best?
I can definitely understand that even if a TC isn't a full 24x36, when
I actually would use one, I'd go to a crop sensor first, so that
doesn't really matter.
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