Auto focus or manual for dance music video?

Started 4 months ago | Questions thread
OP daniel_18 Junior Member • Posts: 28
Re: Auto focus or manual for dance music video?

tamaraw35 wrote:

daniel_18 wrote:

I have one more question. I have been reading about af points and after doing some research I found out that my camera has 9 af points and then 143/3,975 in the live view mode. This is what I've found "The 24.1 megapixel 250D / SL3 offers Dual Pixel CMOS Auto Focusing with a whopping 143/3,975 AF points in live view mode and a more basic 9 AF points when using the optical viewfinder". Do you think that'd be enough when I use autofocus? Or is it hard to tell and depends on the scene? Thanks

First of all, the number of AF points alone does not determine performance. Generally speaking, more AF points will give you a wider area of AF coverage (closer to the edges of the frame) and allow you to focus on smaller objects (like a bird moving in trees).

The 9 points on your camera are phase detect points that essentially measure distance off of the mirror when it is in the down position. You can't capture video with the mirror blocking the sensor, so phase detect is not relevant here. You would have one central point with a diamond pattern of 8 additional surrounding it.

DPAF (dual pixel autofocus) is Canon's on-sensor focus technology and is used in live view when the mirror is locked up. DPAF pretty good in my experience, I have it on my m50 which is basically the mirrorless version of your 250D. More importantly than the additional points, DPAF on our cameras has way better coverage than a phase detect system; 100% height by 88% width. This is quite good for video.

The biggest caveat here is that if you plan to record in 4k (vs 1080p/720p), DPAF is unavailable and the camera just uses basic contrast detect AF which is a bit slower and more prone to hunting. 4k also uses a smaller central area of the sensor and imposes a crop on the regular fov. That can be ok if you have a wide enough lens though, just something to bear in mind.

I know this doesn't really link to my initial question but out of curiosity what do the 143/3,975 AF points in live view mean? Does the viewfinder have 9 points and the live view mode has 143 points? Or am I misunderstanding something here? I'm sorry if this is very basic stuff that I should know. Also, about 4K video, I know it's kind of useless when it comes to autofocus but what about manual focus? Let's say I wanted to shoot in 4K and all manual, would that be doable or is there something wrong with manual focus as well when shooting 4K?

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