sk66
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- Steven
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Even if a TC is optically perfect, there can ONLY be a resulting loss of recorded resolution. The only thing a TC does is magnify the the image circle of the lens. So if that image circle had a resolution of X-lines/mm on the sensor it becomes fewer-lines/mm after magnification.It’s worth mentioning the numbers to be accurate when choosing though as I’m always hearing things like ‘the 1.4x converter has no loss in sharpness’ but it’s around 30% loss when measured.
But there are a lot of other factors that play into it, especially with longer lenses. It is quite probable that some other factor is already limiting recorded resolution so that the TC losses are masked. And note that the losses a (non-existent) perfect TC causes are in resolution/mm (/image); not in resolution/subject area. And if the lens was originally far out-resolving the lens then the losses may not matter; and the increase in sampling (pixels/subject area) may provide some actual gains in recorded resolution.