24-70mm vs. 16-35mm Canon Lens

[William W]

and my pizza is ready to pick up - so I'm not going to do it right now!).

Have a slow red with it and think of me. Cheers - It looks like I am here for another 3 hours . . .

I think.

[_GUI_]

I just wanted to show an image from the 24-70 @ 24mm on APS-C, which show clear distortion (I am not sure if it was 24mm or maybe a bit larger focal length though):

[Blazing fire]

Hi,

So here is how we do it tough, down under . . . a 24 wide open at F1.4 on a 5D, 1/8s, ISO1600 - HH - I can't afford a tripod either



WW

that's quite slow right?

[Colin Southern]

that's quite slow right?

A "rule of thumb" is to use a shutter speed that no slower than the reciprocal of your focal length - which with a 24mm lens would mean a shutterspeed on no lower than 1/25th - whereas Bill was shooting 3 times slower than this. For many this would probably have rise to too much camera shake, but luckily, not for out Bill

[Bill44]

GUI, that sort of distortion will always occur with any lens, but is more noticeable on a WA lens. It is caused by lifting the lens above level. This is why, particularly when taking indoor shots with a WA lens it is vital to keep the lens level. I you point the lens down from level the reverse effect will occur.

If you wish to get technical about it is all to do with the convergence point, and a google will give you more about that than I can explain here.

[William W]

that's quite slow right?

\


Yes.

But the question at the time for me was: could I do it?

I know can pull 1/15s reasonably comfortably from 24mm to 50mm on a 5D (with about 80% success), I get a bit dodgy at 1/15s @ 85mm.

The scene above was taken with the camera cradled in two hands with a sloppy-joe (acting as my bean bag) wrapped around it and then squashed between my two hands and a wooden (vertical) post. I cradled the rear of the camera against my cheek & forehead. I used Mirror Lock Up (after framing it & waiting for the people in shot to be still). I took two frames: inspection on site showed I failed with the first – (camera shake), but I was happy with the second, this one above.

Breathing, breath & heart rate control is important, - don’t laugh – it is just like archery.

For a full explanation as why I had a crack at the scene please read this thread:

Is this too tacky?

In it, I respond to a comments about knowing the Rules, (or not) and applying them (or not).

WW

[Colin Southern]

...I respond to a comments about knowing the Rules, (or not) and applying them (or not).

Or as they say ... "It's amazing what you can do when you don't know what you can't do!"

[William W]

I just wanted to show a couple of images from the 24-70 @ 24mm on APS-C, which show clear distortion, specially the first snapshot (I am not sure if the second was 24mm or maybe a bit larger focal length):

Also: have a close look at the LH side, the edge of the window especially. Place a straight edge against that line.

As well as Convergence, in both images, (as Bill44 mentioned); There is a slight Barrel Distortion, noted, in the top one.

WW

[William W]

Or as they say ... "It's amazing what you can do when you don't know what you can't do!"

Yes, that angle is important too . . .

[McQ]

To the lenses: 16 – 35 and 24 – 70.

I would argue that the 24 – 70 might have more distortion at 24mm than the 16 to 35 has at that same FL.

This is a theoretical point, and based upon the facts of lens design, not a practical test I have done. I have used a 24 – 70 very little and I do not own one. I would expect that if my suspicion is correct, it would be apparent when the lenses were A/B tested, both at F2.8

I hate to generalize, but I would contend that with nearly all zoom lenses have max barrel distortion at their widest and max pincushion distortion at their telephoto end -- and a sweet spot with minimal distortion somewhere in between. If this were applied to the 24-70 and 16-35 discussion, and *if* the 16-35's sweet spot was near 24 mm, then I would think the 16-35 would come out a winner in this regard.

Speaking more practically though: I'm not too familiar with the 16-35mm, but with my 17-40mm f/4L it has much less distortion at 24 mm than my 24-105mm f/4L IS lens has at 24 mm. Perspective distortion is the same though, since they're the same focal length, although the 16-35mm at 24mm ought to be able to exaggerate this type of "distortion" more since it has a closer minimum focusing distance (although I'm not sure if this advantage still applies when both are at 24mm).

I'm not clear whether this is the type of distortion that sedali was wondering about in his original question though...

[Blazing fire]

Just a question, what sideeffects does correcting distortion have?

[Colin Southern]

Just a question, what sideeffects does correcting distortion have?

I'm sure that the purists would say that whenever there is image manipulation there is image damage, but thankfully I'm a perfectionist, not a purist :)

In "Real World" examples probably the biggest thing is the need to crop the image following corrction for barreling, pincushioning and (expecially) perspective projection distortion - so it pays to shoot wide to allow for the extra cropping :)