DPReview member oracle82 writes:
“I know this is a frequent issue, the 35 1.4 vs 23 1.4... but I’ve been wondering about the issue of subject separation with the two. I know that the 35 will have more of a compression factor given the longer focal length. But, I seem to have gone from a 50mm equivalent shooter to more of a 35/40mm equivalent shooter recently. I just prefer the slightly wider view now, and find the 35 to be a little too narrow these days - even though it was the first prime that I bought with my XT-1.
As such, I don’t use the 35 all that much now, and when I do, I find myself backing up for a bit wider view. Of course, then I start to lose some of the blurred background because my subject ends up being further away from me.
I’m not trying to blur out the backgrounds completely, I have other lenses for that. But I do like a slightly blurred graduation when I am shooting certain things at wider focal lengths. Not portraits, just everyday type of photos.
I’ve been toying for awhile with the idea of selling my 35 for the 23, since I don’t use it a lot. It’s a fantastic lens, I just hate having expensive equipment around that I don’t use much.
I’m wondering if the subject separation from f/1.4-2 would be adequate enough with the 23, especially since I can get closer? As I said, with the 35 I find myself backing off to get more in the frame, so I lose a lot of that shallow depth of field. (I really hope this makes sense). If I want more serious subject separation, I have a legacy 58mm that I can use.”
And the award for most confusing answer goes to Christof21 who supplied the link to a website called How Much Blur, which compares the theoretical percentage of blur captured by both lenses at similar distances.
But the question specifically addressed the separation of subject and background at different camera to subject distances. In other words, supplying a link, no matter how erudite it may seem, isn't enough. Relevance is key.
The best response from the same thread attempts to answer the question asked, which distilled simply is this:
I like to shoot [people or other objects] at wider angles. Because of this I have to move farther from my subject when using the 35mm 1,4, which reduces the amount of separation between the subject and the background. Which lens, the 23mm 1,4 or the 35mm 1,4, would return more separation between the subject and the background?
The answer lies in the oracle82's own question: Of course, then I start to lose some of the blurred background because my subject ends up being further away from me.
Any answer concerned with the amount to which a background is blurred and not the degree to which the subject and the background are delineated one from another, is pointless. And so becomes the 35mm's f/1,4 aperture when the subject is moved closer to the background in order to capture a wider view.
The answer is: no, you are not.
The 23mm 1,4 lens will more keenly separate the background from the subject.
Here is the thread: Am I wrong in thinking I could get MORE subject separation with 23 vs 35?