Trying to decide

Decisions, decisions.

I'm trying to decide between a 24mm f/2,8 and an 18-135mm f/3,5-5.6.

I read that the 24 is good for video, but that the 24 is soft at its widest, or lowest aperture numbers, so I probably wouldn't be using the 2.8 aperture anyway. But, with the ASPC crop factor, you wind up with an equivelent focal length of about 38mm, which is pretty close to the old 35mm cameras.

The 24mm prime has really nice wide-aperture background blur, but I can acieve the same thing with a zoom lens, if I have room to back up.

I don't really like to get up in people's faces to take their picture, but the 24 wouldn't be good for that anyway because of the distortion.

I already have a 55-250, so there would be some overlap if I go with the zoom, but I might be able to pick up the 35-40mm focal length.

I have a T8i, so its capable of shooting 4K, but 4K has a crop factor of 1.5, and when you add that to the Canon's native crop factor of 1.6, it's like "Whoa".

It's possible that a 200mm focal length can beome a 600mm shot and you lose the sweeping vistas of a landscape photo.

I don't really like really wide angle shots of sweeping panorama shots of landscape vistas with a teeny, tiny building off in the distance. I wonder, "What's the point?", but then, when you blow it up and see the picture full size, I think, "Darn, that's a nice sharp picture".

I've seen Dig's and others' pictures taken with their 18-135 and T7i combo, and thought, "Those are really nice photos. I bet I could do the same with my T8i".

I'm torn.

Thanks for allowing me my stream of consciousness.

Do you have any thoughts?

Steve Thomass

I've a couple of thoughts:

• The 24mm is small tiny, extremely portable. Think of the lens cap x2.5 to get the lens thickness
• Which 18-135mm? I've heard the USM version is really good.

I think it come's down to if you want a tiny prime lens (presumably shaper (stopped down) than the zoom), or a versatile (but big) zoom.

About the video AF, your camera has DPAF. I think DPAF works just as well with USM lenses (if you get the USM 18-135mm) as with STM lenses (the 24mm).

In fact, I think I heard that some of the STM lenses don't actually focus (for video) that fast (the 50mm STM), and I think the STM 24mm might be one of them.

Jethro B-UK wrote:

About the video AF, your camera has DPAF. I think DPAF works just as well with USM lenses (if you get the USM 18-135mm) as with STM lenses (the 24mm).

In fact, I think I heard that some of the STM lenses don't actually focus (for video) that fast (the 50mm STM), and I think the STM 24mm might be one of them.

Jethro,

I have a 50mm 1.8 (it's probably an STM). I think I'll give it a try for a while and see what I think. I know when I was testing movie servo at long focal lengths, the 50mm seemed to respond pretty quickly by comparison.

Just as an aside, I had been testing movie servo at really long focal lengths and had detected an anomaly. If I focused on something close up and then swung around to something far off. the lens refused to focus at all, unless I started to manually zoom back in. At lower or shorter focal lengths, the lens worked much better, and the 50mm prime was very fast.

Steve Thomas

Yes, do some tests.

Hmm, that's weird.

Jethro B-UK wrote:

Yes, do some tests.

Hmm, that's weird.

Jethro,

Yes. I asked around. I wanted to see if anyone else experienced the same thing at really long focal lengths, or if was just a fluke with my 55-250.

I never really got an answer from anyone though.

Steve Thomas

Jethro,

Here's a short video taken with a 50mm STM lens at 30 fps (IPB light).

You can judge for yourself how rapid the focus changes from near to far.

I learned along the way that 4K autofocus doesn't work nearly that well.

Steve Thomas

oh dear.

I wonder if the t8i is like the m50, in not being able to use DPAF in 4k mode.

Jethro B-UK wrote:

oh dear.

I wonder if the t8i is like the m50, in not being able to use DPAF in 4k mode.

Jethro,

In 4K and time-lapse modes, the T8i uses contrast detection. DPAF is only available in the HD modes.

Steve Thomas

Ah, so it's the same as the m50. Oh well. At least 4k is an option.

I own both of these lenses.  I have used them on T3i, 7D, 7DII and now mostly on T8i.  I often take both of these lenses as a light weight travel kit.  I have been very happy with the images from both lenses over the years.

Just a photo taken with each lens on the T3i from a vacation trip