My experience differs considerably... with regards to TCs.
And I can show you exactly what I'm talking about.
The HD DA 1.4 TC causes a 3% loss in IQ. It increases size 40%. Appropriately used it will ad 37% more detail with the following conditions. The original lens cannot resolve the necessary detail at the distance from the subject.. The subject isn't so far away no lens will resolve the detail. The subject is in the zone between those two. The lens must be a DA* or equivalent. Putting a TC on a soft lens just magnifies the softness. Given those circumstances the increase in detail will be up to 37%, 100% of the time. The variable that makes this a less than hard number is how much of the necessary detail the original lens without TC doesn't resolve. If the original lens in your shoot is revolving 90% of the detail you want, the resulting increase can be no more than the last 10%.
Using a good TC is exactly the same as using a longer, slower lens. Longer lenses don't always produce more subject detail either, if the original lens already was resolving 100% of the critical detail.
Understanding folks saying a TC doesn't ad more detail. - PentaxForums.com
Last edited by normhead; 02-23-2018 at 03:37 PM.