Photoclubalpha

Ok ... probably David will tell me again I have found a good one ...

I'm starting to understand how to really use the lens with its distortion, and tonight I have done some tests after work. I'm continues learning photography and I have never paid attention before to how to handle lens distortion. Please feel free to give me some correction on my picture (thank you in advance).

I'm again really impress by the level of detail this lens can do on the 24MP sensor. And now I'm impress to with the way the lens can handle distortion too.







Full image at 75% compressed with Lightroom from RAM:
http://www.pbase.com/nadeauf/20mm28rs_a900_distortion

Regards,

Frank

The 3rd one looks to show pincushion distortion, which seems very odd for a wide angle like that.

PhotoTraveler wrote:The 3rd one looks to show pincushion distortion ...

The 2nd, too. Strange ...

Frank, have you been playing with Photoshop? Did you introduce these weird-looking distortions on purpose?

-- Olaf

The 20mm has hybrid distortion. If you could see the entire line, it would be a moustache or wave form - barrel in the middle (on the long edge) pincushion towards to corners. On the short edge, it shows pincushion only, but this looks worse than I would have expected. Barrel distortion shows up mainly closer to the centre of the shot.

However, what's bothering the eye in these pix is the horizon level. With a superwide like a 20mm, you must be sure to target the central focus point either exactly at your own eye level, or ideally a fraction above - if your eye level is 5ft 6, you should have the centre of the shot aimed at a height of 6ft. What Frank has done is to aim at 5ft, meaning the camera is ever so slightly angled downwards. This makes verticals diverge, a tiny amount. That looks wrong to the eye, so we notice the distortion more.

Professional architectural photographers don't make their verticals totally parallel, especially with extreme corrections. They 'rack it back' a tiny amount so the verticals converge but only by a couple of millimetres on a A4 page. That looks natural to the eye.

David

I dunno, something not right about using an UWA at eye level, IMO it needs to be used for dramatic effect, and to hell with distortion

I frequently shoot pointing up to buildings, the effect can work rather well at times, converging verticals or not.

I get some wavy distortion on the 19-35mm, but it's not too bad really
A tilt shift would be nice, but you can use the effect of perspective distortion to your advantage.
I couldn't imagine not pointing an UWA up or down, you lose part of the appeal I think if you don't

01af wrote:

PhotoTraveler wrote:The 3rd one looks to show pincushion distortion ...

The 2nd, too. Strange ...

Frank, have you been playing with Photoshop? Did you introduce these weird-looking distortions on purpose?

-- Olaf

No I have done nothing in Photoshop.

I was happy of my result . Probably, I don't really understand again what is a good or a bad distortion in a lens.

For me I was looking at if all my subject was straight and that there was no strange curve.

Now everybody are saying that i have weird things ... is it possible to probably get one or two picture and just put my some arrow where this is ?

Regards,

Frank

Frank,

During the film age (I used Nikon at that time) the 20mm was my favorite lens. When I decided to buy Minolta Digital and before I even had a Minolta body, I got a 20mm (from the Adorama Used Department, for less than 150 US$!) and I wanted to have the same epanuisement (how do you say that in English?) but not. It is just a bad performer on digital.

I sold mine last year in order to finance the Tamron 70-200 2.8. No regret. The KM 17-35 f2.8-4 performs better @ 20mm than the prime.

But lenses are like wines: a good wine is the one you like. Same goes for lenses. If you are happy with the result of your 20mm, why to bother trying to get "public approval"?

A bientot!

pakodominguez wrote:Frank,

During the film age (I used Nikon at that time) the 20mm was my favorite lens. When I decided to buy Minolta Digital and before I even had a Minolta body, I got a 20mm (from the Adorama Used Department, for less than 150 US$!) and I wanted to have the same epanuisement (how do you say that in English?) but not. It is just a bad performer on digital.

I sold mine last year in order to finance the Tamron 70-200 2.8. No regret. The KM 17-35 f2.8-4 performs better @ 20mm than the prime.

But lenses are like wines: a good wine is the one you like. Same goes for lenses. If you are happy with the result of your 20mm, why to bother trying to get "public approval"?

A bientot!

You are right

bfitzgerald wrote:I dunno, something not right about using an UWA at eye level, IMO it needs to be used for dramatic effect, and to hell with distortion

Well, that's how I made my reputation, such as it was, in the 1970s - extreme 17mm stuff with dramatic angles.

There are basically two ways to use extreme wides, for effect, or for architecturally correct rendering (which can also be dramatic). What does not work is something in between, a slightly tilted angle not straight enough to be straight, or steep enough to be dramatic - just a careless sort of composition. Frank was trying for the straight vertical approach.

David

DK is absolutely right about shooting level with a wide. But as other point out, things look weird in there own way from this.

This is why I am a believer that all wide angle lenses should be shift lenses. Since you need to shoot flat, but that leaves either the top or the bottom of the shot not what you want.

This is where high res cameras come into play (along with my preference for wide aspect ratio (16:9 and wider). Take the shot flat as DK states, and then saw off the bottom in the crop to get a wide aspect ratio. Or in the rarer opportunity, saw off the top of the shot.

This was in part the reality I decided on when using the D700 with the 24PCE and 14-24. You could shift the PCE and get the shot. Or you could use the 14-24 at it's widest end and crop back to the same result as the 24PCE. Cropping after the fact is easier and lets you get a wider shot as you can get the corners which you can't with the PCE lens. On the downside the 14-24 flares like mad and takes no filters. A 4/14-24G or ZA could be a great "digital PC" lens. Of course, you don't get tilt like you do on a TS lens, so there is still a need for TS lenses. Also cropping looses pixels and you can't properly frame the shot in the field (unless maybe you make cut outs for in front of the lens)