Extenders, are they worth it?

Milutiche wrote in post #18592818
it takes a bit of the sharpness out of the images but I do like how tight I can get without too much cropping

Depending on your software, you might need to add an extra sharpening layer. I usually do something with a very small radius (CaptureOne internal, not USM), which I do not do with a bare lens. Nik output sharpener has options that works well, not sure about PS. Obviously there is a limit, and you will probably want to use it selectively (which if you have 100s of images, you might also not want to do).

Wilt wrote in post #18617707
Let me try to help...a telextender changes the f/stop of the light that the lens transmits, but more importantly it changes the characteristics of the light striking the sensor -- beyond simply 'light intensity'.
Think of this... focusing a lens at f/2 is different (easier) than focusing the lens accurately and with precision at f/4. Yet the AF sensor has no real problem changing between ambient light intensity of EV0 vs. ambient light intensity of EV2, which is 4X the amount of light.

Yes, the optical geometry and intensity of light are two independent factors for phase-detect AF.

If you turn up the light to maintain exposure as you take a series of photos with a bare lens, then with a 1.4x, then a 2x, then 2x+1.4x, maintaining the light flux on the PDAF sensors does not prevent the focus from failing. The TC brings you closer to threshold of useable light, but it also deteriorates the geometry of the light coming out of the lens, even in ample light. This is where f-ratio is really substantial. It also affects how bright it is in the viewfinder, compared to the ambient light levels outside the camera. The higher the f-number, the darker it is in the OVF compared to what your eyes have adapted to in direct viewing.

fordmondeo wrote in post #18616750
?????

Any way you can simplify that for me?

That's way beyond my technical understanding of the world.

People tend to think of the noise at certain ISOs as something you experience in the out-of-focus areas at 100% pixel view on coarse monitors. That has nothing to do with the subject, though, which could be 12 pixels or 12 million pixels in size. I don't judge the usefulness of an ISO by how bokeh looks at 100%, sharpened, on a monitor. I judge it by what it looks like at the desired subject display size, with only necessary sharpening (which could be none, or even anti-sharpening with noise reduction). Higher ISOs are noisier to your final product when it means less light for your final image, but higher ISOs on almost all cameras mean less noise in the presentation of the final cropped image if it is because of higher optical magnification, rather than a loss of total subject photons. This may seem counter-intuitive, because higher ISOs normally give noisier results, if all you do is increase the shutter speed or stop down with *no* increase in pixels-on-subject. The fact is, most cameras will give you less "subject noise" with the same number of photons from the subject, at the *highest* ISO, because higher ISOs add less noise to a given number of photons, and usually only noisier because they are had in a context where there is significantly less total light from the subject or final cropped composition.

umphotography wrote in post #18583616
I have no clue why it says 5D3. We only had the 150-600 on the 7D2 that day. I think the TC has something to do with this at POTN. I know my Sigma 85 art misreports as well

EXIF embedded in the image shows 5D3.