Sorry, but how is that at all relevant to pictures of a distant bird taken with two relatively narrow-aperture lenses? It's like you're saying @AlanF is also relying on the law of gravity to prevent the photographer, camera, lens and bird from floating away. It's true, but totally irrelevant to the discussion.
Thanks you for answering my questions. What I am trying to do is to give an overview of the effects of the combination of different focal lengths and f-numbers on the overall S/N in a portion of the image in practice, not to provide a precise analytical solution. For a start, different parts of the image have different local S/N, like the deep shadows and highlights at the extremes. The take home message was simply that an f/9 800mm lens doesn't give noisier images for a duck in the middle of an image than a 500mm f/7.1, and probably less noisy, despite an f/7.1 lens often being thought "brighter" than f/9.
It's one of two prerequisites mentioned by me for the validity of the model we both were using. The question was what this prerequisite means.
Indeed, your example is totally irrelevant to the discussion on the effects of the entrance pupil size.
You answered that:
Measuring a person’s height to 10 significant figures is more precise than measuring it to four significant figures. Is that actually relevant for a real world/practical comparison? No.
No, because most of us understand that the difference between F-stops and T-stops for the lenses in question will make no difference in the conclusions drawn from the comparison.
I know. You just don’t seem to get that your examples are only slightly less irrelevant. Pro tip: something that is ‘slightly less irrelevant’ is not relevant.
...I pre-ordered from B&H on 11/3, sold my RF800 on eBay (BIG Mistake with the fees) and am on pins and needles waiting to see if I get my lens close to the shipping date.
Seems to be a slight sharpness edge to the 100-500 + 1.4x but if you, "quickly edited and cropped in PL6," that may be why – PL6 supports the 100-500 + 1.4x with corrections including lens-specific sharpening but does not yet support the 200-800 (nor the 24-105/2.8 that I should have in my hands tomorrow, and not yet even the RF 10-20/4 that came out almost 6 weeks ago...sigh).
I have reported in another thread that I have tested two other 1.4xs and they are no better. https://www.canonrumors.com/forum/t...-rf-100-500mm-1-4xtc-700mm.42961/#post-977995
I had another idea if some body has a good copy of the ef 100-400 4.5-5.6L ii and the ef 1.4 tc iii. There could be a test compare it with the rf 1.4 tc
Thanks. It's useful information. although there's no way that I know of to use the ef 2x with the rf lenses, it does imply a potential for improvement with an rf 2x mk ii. Unfortunately, other than the rumored variable design, I have a hard time thinking another tc will come within the next few years.
The increase in resolution from adding an extender to a lens may vary from lens to lens and I don't think that test would necessarily mean much. @usern4cr and I have both done careful tests with our RF 1.4x TC on the Rf 100-500mm with the R5 and we both find about a 20% increase in resolution, compared with a theoretical 40% for perfection with a wide lens. John's tests are much more complicated than mine, and the clearest ones of his are in Parts 5c of his thread.
