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7Hi lens distortion: too much pincushion?

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Amando Hernández

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First of all, happy Christmas to everybody from Valencia, Spain

On my first outdoors pics made with the Diamge 7Hi, I have observed a high level of pincushion distortion at mid focal distances. I have posted a few examples, together with the focal distance pics were made.

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance

Do you think this is normal? Do you experience similar outcome from your 7x cameras? It's difficult to assess from these examples if my lens is behaving as designed or I have a faulty one. Your opinions will be of great help in deciding about it.

Thanks for your cooperation.

Amando Hernández
Imagenlibre
http://www.imagenlibre.com
 
Amando:

I don't see any pincushion, in fact the lines appear very straight.

You may know, but the tapering verticals are perspective distortion caused by pointing the camera up to get the tops of the buildings in. This happens with any lens. Maybe I'm not seeing what you are concerned about. I haven't noticed any distortion in my photos with a D-7, not even the "gull wing" type at the 28mm setting, but then again. I don't shoot a lot of pictures of buildings.

Good Luck,

Pete
Amando Hernández said:
First of all, happy Christmas to everybody from Valencia, Spain

On my first outdoors pics made with the Diamge 7Hi, I have observed
a high level of pincushion distortion at mid focal distances. I
have posted a few examples, together with the focal distance pics
were made.

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance

Do you think this is normal? Do you experience similar outcome from
your 7x cameras? It's difficult to assess from these examples if my
lens is behaving as designed or I have a faulty one. Your opinions
will be of great help in deciding about it.

Thanks for your cooperation.

Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Click to expand...
 
Amando Hernández said:
First of all, happy Christmas to everybody from Valencia, Spain

On my first outdoors pics made with the Diamge 7Hi, I have observed
a high level of pincushion distortion at mid focal distances. I
have posted a few examples, together with the focal distance pics
were made.

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance

Do you think this is normal? Do you experience similar outcome from
your 7x cameras? It's difficult to assess from these examples if my
lens is behaving as designed or I have a faulty one. Your opinions
will be of great help in deciding about it.
Click to expand...
Merry Christmas to you, Amando.

I'll leave the "technical answer" to those more qualified. Just to give you my layman's observation, "pincushion" in a lense is when the object is distorted to appear narrow at the top and bottom and wide in the middle. Sort of like this. If you take a picture of an item with two straight sides such as " l l " and in your lens/picture it looks like this, " ( ) " that is pincushioning.

What your pics show is what I have heard refered to as "keystoning." It makes straight sides appear to be slanted like the sides of a keystone. This happens when a lense is tilted either up or down from horizontal. It is perfectly normal in all "non tilting" lenses. (Pay attention to what happens with tall buildings with the naked eye when you tilt your head back and look up.)

Specialized cameras exist for architectural and other specialized photography. They involve lenses that are able tilt to compensate for the normal distortion. I am not sure if there is a technique or adapter that will allow you to compensate for keyston effect with the 7xx.

Jim
 
Jim, I think you have this the wrong way round, what you describe is barrel distortion and what you can see in the photo's is pin cushion, where straight lines are curved in at the centre.

We need to hear from others who take building shots to see how theirs compare.

Andy
 
Thanks Jim, for your aswer.

I think this ( ) kind of distortion is called barrel distortion and this ) ( is called pincushion, but I'm not an expert in lens distortions, anyway. I'm aware that if I point up or down with the camera to a building perfectly stright, I'd go (in a perfect lens) something like / \ or \ , perfectly straight although not parellel lines.

Well, I printed these pics and I saw pincushion distortion in a rather scientific way (with a ruler, you know) It's more obvious in this pic:

http://www.pbase.com/image/9451100

see the lines that finish on the upper right corner. They are not straight, as they should have been (on a "perfect" lens). Am I demending too much for a 7X zoom lens? Am I spoiled by the CZ lens (34-102 mm. eq.) on my previous S85 camera?

--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Jim Angelo said:
Amando Hernández said:
First of all, happy Christmas to everybody from Valencia, Spain

On my first outdoors pics made with the Diamge 7Hi, I have observed
a high level of pincushion distortion at mid focal distances. I
have posted a few examples, together with the focal distance pics
were made.

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance

Do you think this is normal? Do you experience similar outcome from
your 7x cameras? It's difficult to assess from these examples if my
lens is behaving as designed or I have a faulty one. Your opinions
will be of great help in deciding about it.
Click to expand...
Merry Christmas to you, Amando.

I'll leave the "technical answer" to those more qualified. Just to
give you my layman's observation, "pincushion" in a lense is when
the object is distorted to appear narrow at the top and bottom and
wide in the middle. Sort of like this. If you take a picture of
an item with two straight sides such as " l l " and in your
lens/picture it looks like this, " ( ) " that is pincushioning.

What your pics show is what I have heard refered to as
"keystoning." It makes straight sides appear to be slanted like
the sides of a keystone. This happens when a lense is tilted
either up or down from horizontal. It is perfectly normal in all
"non tilting" lenses. (Pay attention to what happens with tall
buildings with the naked eye when you tilt your head back and look
up.)

Specialized cameras exist for architectural and other specialized
photography. They involve lenses that are able tilt to compensate
for the normal distortion. I am not sure if there is a technique
or adapter that will allow you to compensate for keyston effect
with the 7xx.

Jim
Click to expand...
 
Thanks Pete for your answer.

I was expecting distortion noticeable at 28 mm. (barrel, in fact, until I found the "wing gull" thread in this wonderful forum). What surprise me is the level of pincushion at 75 mm. I would like to check with other owners of this lens if it's normal or my unit is out of specs (whatever they are, Minolta only knows...)

--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
PeteGanzel said:
I don't see any pincushion, in fact the lines appear very straight.
You may know, but the tapering verticals are perspective distortion
caused by pointing the camera up to get the tops of the buildings
in. This happens with any lens. Maybe I'm not seeing what you are
concerned about. I haven't noticed any distortion in my photos
with a D-7, not even the "gull wing" type at the 28mm setting, but
then again. I don't shoot a lot of pictures of buildings.

Good Luck,

Pete
Amando Hernández said:
First of all, happy Christmas to everybody from Valencia, Spain

On my first outdoors pics made with the Diamge 7Hi, I have observed
a high level of pincushion distortion at mid focal distances. I
have posted a few examples, together with the focal distance pics
were made.

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance

Do you think this is normal? Do you experience similar outcome from
your 7x cameras? It's difficult to assess from these examples if my
lens is behaving as designed or I have a faulty one. Your opinions
will be of great help in deciding about it.

Thanks for your cooperation.

Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Click to expand...
Click to expand...
 
Thanks, Andy, for your answer.

This is what I would like to konw, the experience shooting stright lines (mainly buildings) from other 7x owners to know if I have a defective lens or not.

--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
AndyRPSmith said:
Jim, I think you have this the wrong way round, what you describe
is barrel distortion and what you can see in the photo's is pin
cushion, where straight lines are curved in at the centre.

We need to hear from others who take building shots to see how
theirs compare.

Andy
Click to expand...
 
AndyRPSmith said:
AndyRPSmith said:
Jim, I think you have this the wrong way round, what you describe
Click to expand...
is barrel distortion and what you can see in the photo's is pin
cushion, where straight lines are curved in at the centre.

We need to hear from others who take building shots to see how
theirs compare.
AndyRPSmith said:
Andy
Click to expand...
Click to expand...
Sorry for the error, Andy. After a nip or two of "Holiday Cheer" all of the lines now appear perfectly straight to me. I'll take a serious look into "Pincushion," "Barrel Distortion," "Keystoning," plus any other geometric shapes that may or may not apply apply, on December 26.

Happy Holidays to all.

Jim
 
In this case it's also possible that the building itself isn't straight. :-)

It would be interesting to take a few pictures of graph paper (or "quadrille ruled") at various incident angles to measure this effect. I guess it's possible that some lens distortions that aren't noticeable "head-on" might manifest themselves when taken at an angle as in this shot.

Anyway, that's an interesting looking building. What/where is it?

Cheers,
Jeremy

--

Jeremy L. Rosenberger
http://www.frii.com/~jeremy/
 
Personally I don't see any pin cushion or barrel distortion. I think its the way the camera is angled. Hard to tell from the photos. You need to level the camera and not point it at angle.
 
Jeremy Rosenberger said:
In this case it's also possible that the building itself isn't
straight. :-)

It would be interesting to take a few pictures of graph paper (or
"quadrille ruled") at various incident angles to measure this
effect. I guess it's possible that some lens distortions that
aren't noticeable "head-on" might manifest themselves when taken at
an angle as in this shot.

Anyway, that's an interesting looking building. What/where is it?

Cheers,
Jeremy

--

Jeremy L. Rosenberger
http://www.frii.com/~jeremy/
Click to expand...
--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
 
Amando Hernández said:
Jeremy Rosenberger said:
In this case it's also possible that the building itself isn't
straight. :-)

It would be interesting to take a few pictures of graph paper (or
"quadrille ruled") at various incident angles to measure this
effect. I guess it's possible that some lens distortions that
aren't noticeable "head-on" might manifest themselves when taken at
an angle as in this shot.

Anyway, that's an interesting looking building. What/where is it?

Cheers,
Jeremy

--

Jeremy L. Rosenberger
http://www.frii.com/~jeremy/
Click to expand...
--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Click to expand...
Er...dunno.
But no-ones ever criticised the D7 fo pincushioning.
Try perspective correction then this for other distortions:
http://www.caldwellphotographic.com/D7Distortion.html
Hope this helps,
--
DaveMart
 
All your sample - is not show distortion. It's just simply PERSPECTIVE.

Futher distant from the lens will look smaller. On top of building definitely will look smaller than the bottom if you take the picture on the bottom.
 
widman said:
All your sample - is not show distortion. It's just simply
PERSPECTIVE.
Futher distant from the lens will look smaller. On top of building
definitely will look smaller than the bottom if you take the
picture on the bottom.
Click to expand...
You can check dpreview samples on Canon 1Ds picture #4. It's the same situation.
 
Hi Amando,

Like many others, I can't see any pincushion distortion in your pictures on the screen. If you have to check it with a ruler to detect it, then it is such minor distortion that you can ignore it. I'm sure your lens is normal.

If you want to see real (barrel) distortion, check out a picture I took with my old Fuji 4700 at
http://www.pbase.com/peter_spiro/toronto

-- the thumbnail at the bottom right hand corner of the page. You certainly don't need a ruler to see the curvature of the lake (although in this picture I think it actually looks nice, making it look like you can see the curvature of the earth).

Relative to most wide ratio zoom lenses, the Dimage 7x lens is superb in avoiding distortion.

http://ca.geocities.com/spirope/MinoltaD7.htm
Amando Hernández said:
Well, I printed these pics and I saw pincushion distortion in a
rather scientific way (with a ruler, you know) It's more obvious in
this pic:

http://www.pbase.com/image/9451100
Click to expand...
 
Amando Hernández said:
Thanks to all of you for your suggestions and wisdom. Nice place to
ask for advice.

I've just posted a few examples to help assess the level of
geometric distortion of my camera. A set of bricks taken with
several focal distances. Do you find them close in performance to
your cameras?

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance
--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Click to expand...
--The short answer Amando is, yes. My 7hi looks very similiar. I own a Tamron 28-200 lens for my Maxxum 7 and the distortion isn't as bad as what we see with the 7hi. There is some distortion with that lens also, but that lens retailed for $700 us, a couple of years ago. I guess the bottom line is, you can only pack so much camera into a $1000 package.
Sol
 
Thanks, Sol, for your answer. You know, my only purpose for this thread was knowing if I had a defective lens or not. This is my first "encounter" with such a big zoom, and I know there is a price to pay for it. Well, that's the state of the art at that price level, specially if (like me), one's looking for 28 mm. The only alternative is the Coolpix 5000, which I discarded for other reasons.

So I have to get accustomed to the lens' behaviour and take the most out of it. The camera is anyway terrific so I expect to keep it for some years, until price and technology produce the DSLR for the masses.

Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Sol said:
Amando Hernández said:
Thanks to all of you for your suggestions and wisdom. Nice place to
ask for advice.

I've just posted a few examples to help assess the level of
geometric distortion of my camera. A set of bricks taken with
several focal distances. Do you find them close in performance to
your cameras?

- http://www.pbase.com/ahmonge/dimage_7hi_lens_performance
--
Amando Hernández
Imagenlibre
http://www.imagenlibre.com
Click to expand...
--The short answer Amando is, yes. My 7hi looks very similiar. I
own a Tamron 28-200 lens for my Maxxum 7 and the distortion isn't
as bad as what we see with the 7hi. There is some distortion with
that lens also, but that lens retailed for $700 us, a couple of
years ago. I guess the bottom line is, you can only pack so much
camera into a $1000 package.
Sol
Click to expand...
 
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