Actually Pentax makes DSLRs and maybe some some day soon they will be the only DSLR manufacturer.
Sony abandoned DSLRs because they were unable to compete successfully in that market.
Quite right. The RF 100-400mm is no less normal than the EF 100-400mm L. And, logically speaking, it is more "normal" because the 100-400mm L is by definition special as it has a red ring and is white to show it is "superior".
Not quite the same build quality as the EF version with more plastic which makes it lighter (which I prefer) and the odd limitation of restricted zoom range with extenders (which really irritates me as it makes it far less versatile for no reason) but very similar otherwise and slightly better overall performance.
No. Because the 70-300 non-L lenses were not particularly good lenses. The 100-400 is a decent lens with good sharpness. I guess you could argue it fills a similar niche if you ignore image quality. It might be better to compare it to the EF-S 55-250. An inexpensive lens that delivered decent image quality at a low price.
I have found, as have many others, that this is a remarkable lens. Small, light, just as good at 400 as the Mk 1 100-400L. Canon has never offered such quality at 400 before at a price most can afford. I have had the Mk2, the Tammy, the Siggy. The Canon RF beats both 3rd party versions in all aspects. Ok, maybe not all, it doesn't come with A HOOD.Spiritual successor, then.
It takes the same hood as the 70-300 so there are plenty of knock-off hoods costing just a few $/£. I found like you that my copy of the R beats the Tammy and Sigma, and my Mk 1 was soft.
Not sure if your experience was with the Mark I version of the 70-300 non-L, but the Mark II version is a really fine lens. Dustin Abbott did a review and compared it with the 70-300 L, and found little or no difference in sharpness. My experience with the lens is similar - and in fact the 70-300 II non-L was sharper cropped to the same size photo at 300mm as my Sigma 100-400mm at 400mm. I consider it a real "steal" among the non-L lenses for those looking for cheaper alternatives.
I think one of the things that differentiates the L-series lenses from consumer grade lenses is quality control. Copy variation occurs for all of them, but it’s less common and less extreme for the high end lenses.
I agree completely, that the L-lenses (or higher end lenses regardless of brand) will be more consistently good. That being said, over the years I have owned or rented 3 copies of the 70-300 II (non-L) and they have all been very close to as sharp as the L version. And, yes, I always try to buy lenses from a place or seller (on Ebay or similar) that accepts returns and definitely agree with your recommendation to do so.
I'm curious if you owned the 70-300L? Sharpness (as most know) is only one aspect of a lens' character and the 70-300L renders gorgeously. The non L is sharp but for me, it ended there. The LatCA and axial CA were very pronounced as well. The distance scale LCD...just one more thing to go wrong? Didn't like mushy sunstars at f/16 either.
