Amazingly basic question time

Does the plane of focus change when you zoom in or out? (on a zoom lens, obviously)

Muchas gracias!

If you're asking if a zoom lens will hold focus throughout the entire zoom range, the answer is...

Not unless it's "Parfocal" and 99% of Canon lenses for still cameras are not.

Ah, so basically I can't manually focus my 24-70 at 70mm with maxed out live view, then zoom back out to 24? Bummer, but thanks .

If you can't get a sharp shot using the 10x live view at 24mm - you may have another issue?

I haven't actually tried it yet, just wondered. For star photography, I thought maybe the extra zoom could come in handy.

armis wrote in post #14705601
I haven't actually tried it yet, just wondered. For star photography, I thought maybe the extra zoom could come in handy.

Unless you mean celebrity photography, setting the focus ring to infinity should be ok at any focal length. Most stellar objects are quite a long way away. Quite a lot of them are even further than that.

JohnB57 wrote in post #14705638
Unless you mean celebrity photography, setting the focus ring to infinity should be ok at any focal length. Most stellar objects are quite a long way away. Quite a lot of them are even further than that.

Yeah, you know, that's what I thought too. The first thing I realized when I gave it a try is that it doesn't work: setting the ring at infinity is actually too far, you need to focus a little before that. Either that, or maybe my distance scale is off: regardless, infinity focus didn't work for me.

JohnB57 wrote in post #14705638
Unless you mean celebrity photography, setting the focus ring to infinity should be ok at any focal length. Most stellar objects are quite a long way away. Quite a lot of them are even further than that.

Setting the ring to infinity is a good way of getting nothing in focus, as that actually makes the lens focus "beyond" infinity.

Armis, look up hyperfocal distance and just use that as a guide as to where to adjust your focus ring, or focus on something really far away during the day so you can see where you need to focus later at night.

If you mean setting the focal point as far away as it will go, that is not infinity focus. Most lenses are designed to go beyond it. This is marked on the distance scale on most lenses that still have them.

JohnB57 wrote in post #14705638
Most stellar objects are quite a long way away. Quite a lot of them are even further than that.

Holy crap that made me laugh.

I was being a little tongue in cheek, but if you use the focus scale and match the appropriate FL line with the vertical part of the elongated "L", that's infinity focus - it works on all my lenses.

Thus...

JohnB57 wrote in post #14706397
I was being a little tongue in cheek, but if you use the focus scale and match the appropriate FL line with the vertical part of the elongated "L", that's infinity focus - it works on all my lenses.

No, I get that - but on my 24-70, when I tried it, it didn't work. Honest. I didn't throw the focus ring as far as it'd go, just lined it up with the infinity marker, and took a test shot, and it was blurry.

I also tried hyperfocal focusing (somewhat familiar with the concept since I got my manual 14mm lens), which I guessed was between 5-10 metres (no calculator with me). I placed the ring at 10m, took a test shot - blurry. That's the point where I went "oh screw this " and ended up taking a few shots, turning the focus ring a little bit every time, and found the sweet spot through trial and error (although having the presence of mind of using live view would have saved a lot of trouble).

I guess my distance scale must be off.

^ armis: Did you turn off AF, before setting infinity focus? If you didn't, AF will just reacquire focus(and probably not where you want) again when you 1/2 push the shutter button.

armis wrote in post #14710234
I guess my distance scale must be off.

No, I don't think so. The problem is that stars are the toughest test of focussing because they're very bight points of light.

Focussing at the hyperfocal distance is fine in most cases. But it's only objects at the hyperfocal distance that will actually be in focus. Objects in front and behind that distance aren't in focus - they're just acceptably close to being in focus. But that word 'acceptably' applies to normal shooting - where you're not going to notice that the leaves on a tree a mile away are slightly blurred.

But stars are incredibly demanding targets - especially if you're going to be looking at them zoomed in to 100%. So you really do need them to be on the plane of focus (or acceptably close, where what is acceptable is a lot closer than is normally used).

So LiveView, preferably zoomed in, is the best option.

Buzz Lightyear lenses that focus to infinity and beyond...