Convex

Zeckson Chow · 8th May 2005

Guys, need your expert advice on this... Please take a look at this picture.

Besides it is slightly slanted, did you all notice that the picture is also slightly convex? What actually causes this? I tried at different EXIF but still get the same result. Is it a D70 problem? Do you guys encounter this problem before? Or is it my settings or skills?

Please advice. Thanks.

ZeroDivine · 8th May 2005

the lens

Zeckson Chow · 8th May 2005

The lens? Could you enlighten further please? Or is there any websites that I can do some reading up? I don't know what this problem is called. I am using the Sigma AF 28mm - 300mm F3.5 - F6.8 Telephoto Zoom.

TMC · 8th May 2005

its your freaking lens problem.

go search for barrel distortion and pincushion effect.

timlim · 8th May 2005

There's probably a bit of distortion from the lens, but I think it's greatly exaggerated by the shape of the stairs more than anything else!

Zeckson Chow · 8th May 2005

Originally Posted by TMC

its your freaking lens problem.

go search for barrel distortion and pincushion effect.

Do you need to use the word "freaking" here? My FREAKING lens?

TMC · 8th May 2005

You read it right the first time. its a part of my vocabulary for everyday usage for non-abusive purposes.

or simply put, its the way I speak.

Zeckson Chow · 8th May 2005

Originally Posted by TMC

yeah your freaking lens. its a part of my vocabulary for everyday usage.

I see. Sorry, I take it as quite rude? Hope I am wrong.

Expiredyoghurt · 8th May 2005

relax lah ZC =) ... he's probably just as pissed at barrel distortion ...

anyways its a common problem ... and alot of people are pissed by the lenses that cause it .. thus the use of 'freaking'

Zeckson Chow · 8th May 2005

I see. Okies. No problem. Maybe I am just sensitive lah after all the slamming and jamming...

KNIGHT ONG · 8th May 2005

You are getting over-sensitives ..

Zeckson Chow · 8th May 2005

I'm sorry guys... Especially to TMC. I misunderstood you.

ricohflex · 8th May 2005

It may not be your lens.
It may be the effect of tilting a wide angle lens upwards.
This distortion is why people made view cameras and tilt/shift lenses.

It may also be an optical illusion.
Your photo has many small straight lines formed by the steps.
And two curves formed by the sides of the staircase.
The picture tricks your eyes into thinking there is a convex.
There may not be a convex.

espn · 8th May 2005

Originally Posted by ricohflex

It may not be your lens.
It may be the effect of tilting a wide angle lens upwards.
This distortion is why people made view cameras and tilt/shift lenses.

This is perspective distortion, well known when you shift your glass upwards to shoot.

Originally Posted by ricohflex

It may also be an optical illusion.
Your photo has many small straight lines formed by the steps.
And two curves formed by the sides of the staircase.
The picture tricks your eyes into thinking there is a convex.
There may not be a convex.

Very simple, take a ruler or something straight and measure. I just did and found it to be pincushion.

MyNikon · 8th May 2005

Even our eyes don't see things "straight" all the time.

yanyewkay · 8th May 2005

time to get a (or 3) constant f2.8 trinity.

espn · 9th May 2005

They're not spared from barrel and pincushion either. Take 17-35 for example, at 17mm wide, I note barrel distortion.

ibs · 9th May 2005

Its barrel distortion. if you are particular abt it, take a couple of steps back, use a tele and compose from 50 mm onwards. Also, don't tilt your lens.

rayshade · 9th May 2005

It is quite difficult to find a barrel distortion free lens esp on a zoom. The 17-35 is not much different from the 18mm/2.8 the prime is slightly better. I've ever tried a Carl Zeiss 20mm/f2.8 Jena with M42 on the D70. This east German lens exhibits the least barrel @ S$300. I almost bought it only to discover the lens does not have lens hood and really not in the best condition for heavy use. CZ is indeed a classy product even the sub par Jena outperforms many.

espn · 9th May 2005

Right, it's just how well minimised the problem can get, cheap or not, all glasses do suffer, the good point is that on DX format DSLRs the 17-35 looks great across all range

8th May 2005	#1
Zeckson Chow Senior Member Join Date: Mar 2005 Location: Currently in Bangkok, Thailand Posts: 3,945	Convex Guys, need your expert advice on this... Please take a look at this picture. Besides it is slightly slanted, did you all notice that the picture is also slightly convex? What actually causes this? I tried at different EXIF but still get the same result. Is it a D70 problem? Do you guys encounter this problem before? Or is it my settings or skills? Please advice. Thanks. __________________ I am not a photographer. http://www.flickr.com/photos/zeckson...7614422002610/

8th May 2005	#3
Zeckson Chow Senior Member Join Date: Mar 2005 Location: Currently in Bangkok, Thailand Posts: 3,945	The lens? Could you enlighten further please? Or is there any websites that I can do some reading up? I don't know what this problem is called. I am using the Sigma AF 28mm - 300mm F3.5 - F6.8 Telephoto Zoom. __________________ I am not a photographer. http://www.flickr.com/photos/zeckson...7614422002610/

8th May 2005	#4
TMC Senior Member Join Date: Sep 2004 Location: Beyond Space-Time Continuum Posts: 5,921	its your freaking lens problem. go search for barrel distortion and pincushion effect. __________________ Selling: 32GB Thumbdrive - Patriot Xporter XT 120sgd (Price reduced)

8th May 2005	#7
TMC Senior Member Join Date: Sep 2004 Location: Beyond Space-Time Continuum Posts: 5,921	You read it right the first time. its a part of my vocabulary for everyday usage for non-abusive purposes. or simply put, its the way I speak. __________________ Selling: 32GB Thumbdrive - Patriot Xporter XT 120sgd (Price reduced) Last edited by TMC; 8th May 2005 at 05:48 PM.

8th May 2005	#10
Zeckson Chow Senior Member Join Date: Mar 2005 Location: Currently in Bangkok, Thailand Posts: 3,945	I see. Okies. No problem. Maybe I am just sensitive lah after all the slamming and jamming... __________________ I am not a photographer. http://www.flickr.com/photos/zeckson...7614422002610/

8th May 2005	#2
ZeroDivine Member Join Date: Sep 2004 Posts: 1,623	the lens

8th May 2005	#5
timlim Member Join Date: Mar 2005 Posts: 529	There's probably a bit of distortion from the lens, but I think it's greatly exaggerated by the shape of the stairs more than anything else!

8th May 2005	#9
Expiredyoghurt Member Join Date: Dec 2004 Location: Yishun Posts: 1,385	relax lah ZC =) ... he's probably just as pissed at barrel distortion ... anyways its a common problem ... and alot of people are pissed by the lenses that cause it .. thus the use of 'freaking'

8th May 2005	#11
KNIGHT ONG Senior Member Join Date: Dec 2003 Location: Snow Mountain Posts: 5,729	You are getting over-sensitives .. __________________ AMPA * Studio * J team

8th May 2005	#13
ricohflex Senior Member Join Date: Feb 2005 Location: sing Posts: 1,540	Zeckson convex It may not be your lens. It may be the effect of tilting a wide angle lens upwards. This distortion is why people made view cameras and tilt/shift lenses. It may also be an optical illusion. Your photo has many small straight lines formed by the steps. And two curves formed by the sides of the staircase. The picture tricks your eyes into thinking there is a convex. There may not be a convex.

8th May 2005	#15
MyNikon Member Join Date: Apr 2005 Location: Bedok North Posts: 290	Even our eyes don't see things "straight" all the time.

8th May 2005	#16
yanyewkay Senior Member Join Date: Sep 2004 Location: Cons digger. Posts: 4,046	time to get a (or 3) constant f2.8 trinity. __________________ “How fortunate for leaders that men do not think.” - Adolf Hitler

9th May 2005	#17
espn Deregistered Join Date: Dec 2002 Location: Planet Nikon Posts: 22,045	They're not spared from barrel and pincushion either. Take 17-35 for example, at 17mm wide, I note barrel distortion.

9th May 2005	#18
ibs Member Join Date: Oct 2004 Posts: 371	Its barrel distortion. if you are particular abt it, take a couple of steps back, use a tele and compose from 50 mm onwards. Also, don't tilt your lens.

9th May 2005	#19
rayshade Member Join Date: Dec 2004 Posts: 335	It is quite difficult to find a barrel distortion free lens esp on a zoom. The 17-35 is not much different from the 18mm/2.8 the prime is slightly better. I've ever tried a Carl Zeiss 20mm/f2.8 Jena with M42 on the D70. This east German lens exhibits the least barrel @ S$300. I almost bought it only to discover the lens does not have lens hood and really not in the best condition for heavy use. CZ is indeed a classy product even the sub par Jena outperforms many. Last edited by rayshade; 9th May 2005 at 11:05 AM.