dgolfnut wrote:
I am an amateur enthusiast and shoot landscapes, nature - still and in-flight, night scenes and family events with a Nikon D850.
I have 24 & 50mm F1.8 primes. I've thought about a 1.4 or 1.2 for better low light performance but am concerned about DOF. As I've thought more about it, I realize I rarely even use the 1.8 wide open. I have gotten some nice night night shots handheld or minimally braced with the 1.8.
Maybe I just don't know enough about what tool to use in what situation.
So the question is - in what situations is an f1.4 or 1.2 the right tool for the job and what will it give you that a much less expensive 1.8 will not?
I am an amateur enthusiast and shoot landscapes, ... (
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This question almost never gets answered completely or correctly. The correct answer? "It depends."
In the past, I concurrently owned 50mm f1.8, f1.4, and f1.2 Zuiko lenses for my Olympus film cameras. All were current models at the time. I had bought them sequentially in that same order, and progressively upgraded to the wider apertures. Let me address a few things that might help you think intelligently about your choice here.
First...depth of field is not even a consideration between a f1.8 and even a f1.2 lens, especially at 50mm. The depth of field is so shallow at f1.8 that it is impossible to observe a meaningful difference when moving even all the way to f1.2. Now with a wide angle, there will be a bigger difference, but it is still not a significant issue. And you still have the smaller f stop available if you should need it. You don't have to shoot at f1.2 just because you have a f1.2 lens.
But the difference in exposure is a full stop, and that can be significant. I don't generally use a 50mm lens for night sky photography, but I could. The lens I use is an f2.8 wide angle, and my normal exposure is f2.8, 25 seconds, ISO 4000. If I had a f1.2 lens (2.5 additional stops of exposure), I could drop ISO to 2000 and exposure time to 10 seconds. That is a huge difference. And everything is at infinity, so I don't care about depth of field at all.
For a given focal length, lenses with larger f stops are generally of higher design and construction grades. I know that for my Olympus, there was a huge difference in quality and construction moving from the f1.8 to the f1.2. The f1.8 was clearly a "beginner" lens. Very lightweight, simple optical design, slightly sloppy operation, very soft corners, marginal sharpness and color transmission. The f1.4 was an "enthusiast" lens...better construction, very smooth operation, better image quality. But the f1.2 was a truly professional grade lens. Sharp all the way to the corners, beautifully sharp and colorful images, and built both like a tank and a fine watch. Of course, the prices for those lenses progressed accordingly.
So to really make a good choice between or among these lenses, you need to consider a lot more than depth of field (which doesn't matter). You need to decide whether your usage patterns would suggest a more rugged lens, and whether you would appreciate the performance of a higher grade lens. Also consider that a 50mm f1.2 may weigh twice as much as a 50mm f1.8. Does that matter to you?