M50ii + EF-S 55-250mm STM + Kenko SHQ 1.5x Teleconverter

JasonS70 wrote:

Well I finally managed to be in a position to take a couple of direct comparison photos of a bird, one with the converter one without. I had a very accommodating Kestrel hang around for me

I am redrawing my conclusion that there is isn't much of a difference in image quality between converter and non-converter photos. There is a clear difference, to the negative, when using the teleconverter. So for me it is going to be shelved and I will go back to relying on cropping

Both photos are straight from DPP with the same edits and are full size

Cheers

Jason

Teleconverter

No teleconverter

Thanks for sharing your results. There are several factors that can explain why you're seeing results that are not as good as what I typically get.

The shots are taken at f8, which is a little beyond the diffraction limit of the 24 MP sensor. If the chip from the TC was removed and the TC shot was really at f11 (f8 setting + 1 stop unreported loss from the TC) then it would most definitely look soft like that. From the exposure data alone, the TC shot appears to have had over a stop more exposure, yet looks darker, indicating it may have been shot at f11 since the lighting looks almost the same.

DPP will do a pretty good job for the raw EF-S 55-250 IS STM, but won't have the corrections right for the 55-250 + a teleconverter which needs different lens corrections, including a bit more CA correction. if you're comparing both images using the same set of DPP corrections, or if DPP didn't know what the lens + TC combo was and didn't use corrections, that could also explain why your TC shots don't look as good.

I've found that you can manually correct the TC images very nicely using DxO PL5, on top of the EF-S 55=250 optical corrections DxO has for that lens. TC images need a custom CA correction and also specific sharpening settings. Also in general DxO's de-mosaicing seems better that DPP 4.

Your comparison uses different focal lengths of the EF-S 55-250 to simulate the same final image size, so it's not really an apples to apples comparison. The performance of the 55-250 mm, or perhaps your copy, may be worse optically at the focal length used for the TC shot vs the one used for the non-TC shot.

The non-TC shot has the bird larger at the pixel level than it is in the TC shot, so it will show more detail since it is a more magnified, this will make the non-TC picture appear sharper since it can show slightly more fine detail in the feathers and branches.