SLR lens on DSLR's

In article ,
David J. Littleboy wrote:
>
>Oh, quite the contrary, they do. The limiting practical resolution of the 5D
>sensor is 40 lp/mm. That's all, folks. Anything over that is unused. That
>means that even the junkiest of recent lenses cough up lovely sharp images.
>Someone over at dpreview reports great results with the Canon 55-200
>el-cheapo kit zoom for the Rebel. And the Tamron 28-75/2.8 is wonderful on
>the 5D.

Got a Flektogon 35mm f/2.4 on eBay for 40 Euros from a chap in Germany in
M42 screw mount the other week for use on the 5D. It's absurdly good, and
doesn't show any of this so-called "digital chromatic abberation" that there
seems to be this superstition about.
 >> Stay informed about: SLR lens on DSLR's 

On Sun, 16 Oct 2005 17:10:49 +0900, "David J. Littleboy"
wrote:

>
>"Rich" wrote:
>> On Sat, 15 Oct 2005 22:31:10 -0400, Bill wrote:
>>>
>>>You don't actually believe this stuff...do you?
>>
>> Fine, ignore it. And ask yourself WHY Canon would post
>> samples images from the 5D that exhibited some of the problems
>> people have mentioned. Reason?
>
>Their advertising department is stupid and blind and doesn't have a clue
>about photography.
>
>There are lots of sharp images taken with the 17-40 and 16-35. It is true
>that FF digital is much more like medium format than a P&S camera, and that
>you sometimes have to know what you are doing to get good images. Standard
>things like making sure the corners are within the DOF.

The one photo that exhibited the problems was a landscape. How far
out do you have to be to be withing the DOF?
>
>> They had no choice because they
>> didn't have a suitable (in that case) wide angle lens to use with the
>> camera. There are some lenses in their vast stable of lenses that
>> work reasonably well. Perhaps their new 60mm macro.
>> But now you've got the owners of 5Ds (see the Fred Miranda site)
>> modifying their Canons to take Leica glass. Ask yourself why.
>
>My guess is that they tested the Canon lenses in AF mode.

Doesn't the AF in Canon's work?

>> Those big FF sensors simply do not tolerate or hide aberrations
>> in the lenses that film would.
>
>Oh, quite the contrary, they do. The limiting practical resolution of the 5D
>sensor is 40 lp/mm. That's all, folks. Anything over that is unused. That
>means that even the junkiest of recent lenses cough up lovely sharp images.

Hence the stampede by pros to obtain Canon's cheap kit lenses, right?

>Someone over at dpreview reports great results with the Canon 55-200
>el-cheapo kit zoom for the Rebel. And the Tamron 28-75/2.8 is wonderful on
>the 5D.
>
>David J. Littleboy
>Tokyo, Japan
>

Well, at least you don't hate aftermarket lenses.
-Rich
 >> Stay informed about: SLR lens on DSLR's 

"MarkH" wrote:
> Rich wrote:
>>
>> SLR lens on DSLR can mean....CA, spherical aberration, etc.
>> Why? Because old SLR lenses do not control aberrations well enough
>> to allow digital sensors to function as well as they can. To do this,
>> you need ED glass and aspherical elements, something rare on old SLR
>> lenses, even L-series lenses.
>> As time goes on, even hold outs like Canon will start dedicating lens
>> design to digital and pros and amateurs will slowly get rid of their
>> ancient FILM lenses.
>> -Rich
>
> You know, if you don't want people to think you are a crackpot then you
> should mention that what you say only applies to wide angle lenses on FF
> digital cameras.

It doesn't even apply there. Even the Stigma 12-24 works fine on FF (if you
get a good copy).

> The problem is the light hitting the sensor at an angle,
> long lenses don’t have this problem and smaller sensors don't use the
> light
> on the edge of the image circle.

But now you're not thinking. You might want to consider how far the rear
element in a wide angle lens is from the sensor in a DSLR.

Now that you've thought about that, look at the size of said rear element.
(I've never seen a (FF) wide angle with a rear element that's any larger
than that of the 50/1.4 or that's any closer to the sensor (remember, it has
to clear the mirror))

The "light hitting the sensor at an angle" bit is simply dead wrong lying
FUD from camera companies that don't have a FF sensor. All SLR wide angle
lenses are retrofocus lenses and have lower angles of incidence than the
50/1.4.

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: SLR lens on DSLR's 

"David J. Littleboy" wrote in


>
> "MarkH" wrote:
>> Rich wrote:
>>>
>>> SLR lens on DSLR can mean....CA, spherical aberration, etc.
>>> Why? Because old SLR lenses do not control aberrations well enough
>>> to allow digital sensors to function as well as they can. To do
>>> this, you need ED glass and aspherical elements, something rare on
>>> old SLR lenses, even L-series lenses.
>>> As time goes on, even hold outs like Canon will start dedicating
>>> lens design to digital and pros and amateurs will slowly get rid of
>>> their ancient FILM lenses.
>>> -Rich
>>
>> You know, if you don't want people to think you are a crackpot then
>> you should mention that what you say only applies to wide angle
>> lenses on FF digital cameras.
>
> It doesn't even apply there. Even the Stigma 12-24 works fine on FF
> (if you get a good copy).
>
>> The problem is the light hitting the sensor at an angle,
>> long lenses don’t have this problem and smaller sensors don't use the
>> light
>> on the edge of the image circle.
>
> But now you're not thinking. You might want to consider how far the
> rear element in a wide angle lens is from the sensor in a DSLR.

Why? What does this have to do with the rear element? I am only
thinking about the light path for the light entering the lens at an
angle, something that is not an issue on a long lens (when you capture a
field of view of less than 40 degrees the light will be close enough to
parallel to the sensor to not be an issue).

> The "light hitting the sensor at an angle" bit is simply dead wrong
> lying FUD from camera companies that don't have a FF sensor. All SLR
> wide angle lenses are retrofocus lenses and have lower angles of
> incidence than the 50/1.4.

This seems counter intuitive to me, I have read in more than one review
site about the problems with the light hitting the microlenses at an
angle causing light falloff.

However I am not happy to trust the review sites (nor you for that
matter), I really need to see some comparisons between the images
captured with a FF digital with an ultra-wide angle lens and the same
lens on a film SLR. Then I could see if the problem exists and how bad
it is. I would also like to see how much aperture difference would be
needed to fix the problem if it exists. I suspect that the problem with
wide angle lenses at a wide aperture also occurs with film and is not
dramatically worse (and may be no worse perhaps) on a FF D-SLR. I don't
know why I haven't seen such a comparison, the Canon film SLRs are not
rare - it can't be all that hard to do such a test.

But I stand by my point that the problem (if it exists) does not apply
to long lenses and also on smaller sensors you don't see those edges or
corners (because they are cropped off). Therefore there is definitely
no need for special 'digital' lenses except maybe for ultra-wide lenses
for use on FF D-SLRS (even then there is not consensus on that need).



--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 5-September-05)
"The person on the other side was a young woman. Very obviously a
young woman. There was no possible way she could have been mistaken
for a young man in any language, especially Braille."
Maskerade
 >> Stay informed about: SLR lens on DSLR's 

Rich wrote in


> Well, because the 5d is much less expensive than the big flagship
> Canon, we should begin to see many more examples of photography from
> it. At that point you'll see overall how well it works with Canon's
> legacy glass. Problem is, I don't know if Canon is even making new
> lenses that specifically cater to digital sensors and their
> differences from film so comparisons are a problem, unless someone
> grafts (as is being done) other mfgs lenses onto the bodies.
> -Rich

How hard would it be to compare the lens on a 5D with the same lens on a
film SLR?

I still say this (possible) problem will not occur at all on longer lenses
which only capture a narrow FoV and therefore focus nearly parallel light
rays onto the sensor. This (possible) problem will also rarely show itself
on the other D-SLRs that have a smaller sensor (since the problem is likely
to be in the corners which the smaller sensor crops).


--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 5-September-05)
"The person on the other side was a young woman. Very obviously a
young woman. There was no possible way she could have been mistaken
for a young man in any language, especially Braille."
Maskerade
 >> Stay informed about: SLR lens on DSLR's 

"MarkH" wrote:
> "David J. Littleboy" wrote:
>> "MarkH" wrote:
>>> Rich wrote:
>>>>
>>>> SLR lens on DSLR can mean....CA, spherical aberration, etc.
>>>> Why? Because old SLR lenses do not control aberrations well enough
>>>> to allow digital sensors to function as well as they can. To do
>>>> this, you need ED glass and aspherical elements, something rare on
>>>> old SLR lenses, even L-series lenses.
>>>> As time goes on, even hold outs like Canon will start dedicating
>>>> lens design to digital and pros and amateurs will slowly get rid of
>>>> their ancient FILM lenses.
>>>> -Rich
>>>
>>> You know, if you don't want people to think you are a crackpot then
>>> you should mention that what you say only applies to wide angle
>>> lenses on FF digital cameras.
>>
>> It doesn't even apply there. Even the Stigma 12-24 works fine on FF
>> (if you get a good copy).
>>
>>> The problem is the light hitting the sensor at an angle,
>>> long lenses don’t have this problem and smaller sensors don't use the
>>> light
>>> on the edge of the image circle.
>>
>> But now you're not thinking. You might want to consider how far the
>> rear element in a wide angle lens is from the sensor in a DSLR.
>
> Why? What does this have to do with the rear element?

"The problem is the light hitting the sensor at an angle"

The angle with which the light hits the sensor is determined by the geometry
of what happens when the light passes from the rear of the lens to the
sensor.

> I am only
> thinking about the light path for the light entering the lens at an
> angle, something that is not an issue on a long lens (when you capture a
> field of view of less than 40 degrees the light will be close enough to
> parallel to the sensor to not be an issue).

The angle with which the light enters the lens has nothing to do with how it
hits the sensor.

>> The "light hitting the sensor at an angle" bit is simply dead wrong
>> lying FUD from camera companies that don't have a FF sensor. All SLR
>> wide angle lenses are retrofocus lenses and have lower angles of
>> incidence than the 50/1.4.
>
> This seems counter intuitive to me, I have read in more than one review
> site about the problems with the light hitting the microlenses at an
> angle causing light falloff.

Yes, and none of them are thinking. All SLR wide angle lenses are what is
called 'retrofocus' designs; they are designed so that the rearmost element
of the lens is far enough away from the sensor that there's room for the
mirror to swing. The angles of incidence are the same for everything 50mm
and wider. (Actually, the 50/1.4, with its large rear element, has the
highest angles of incidence of any of these lenses.)

> However I am not happy to trust the review sites (nor you for that
> matter), I really need to see some comparisons between the images
> captured with a FF digital with an ultra-wide angle lens and the same
> lens on a film SLR.

Quite a few were published when the 1Ds first came out. The film images
looked sick in comparison to the 1Ds.

> But I stand by my point that the problem (if it exists) does not apply
> to long lenses and also on smaller sensors you don't see those edges or
> corners (because they are cropped off).

Yes: most decent lenses 85mm and longer have dead flat MTF charts all the
way out to the corners and beyond. It's only wide angle lenses that have
funky corners.

> Therefore there is definitely
> no need for special 'digital' lenses except maybe for ultra-wide lenses
> for use on FF D-SLRS (even then there is not consensus on that need).

Yep, again.

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: SLR lens on DSLR's 

"Rich" wrote:
> "David J. Littleboy" wrote:
>>
>>There are lots of sharp images taken with the 17-40 and 16-35. It is true
>>that FF digital is much more like medium format than a P&S camera, and
>>that
>>you sometimes have to know what you are doing to get good images. Standard
>>things like making sure the corners are within the DOF.
>
> The one photo that exhibited the problems was a landscape. How far
> out do you have to be to be withing the DOF?

Again, why worry about one bad image when there are lots of good images out
there. Read the reviews of the 17-40 on Luminous Landscape or W. Castleman's
site. Nice sharp corners.

>>My guess is that they tested the Canon lenses in AF mode.
>
> Doesn't the AF in Canon's work?

AF (Canon or otherwise) doesn't make sense for landscapes. You need to focus
manually. Especially with full frame with its 1.6x shallower DOF.

>>> Those big FF sensors simply do not tolerate or hide aberrations
>>> in the lenses that film would.
>>
>>Oh, quite the contrary, they do. The limiting practical resolution of the
>>5D
>>sensor is 40 lp/mm. That's all, folks. Anything over that is unused. That
>>means that even the junkiest of recent lenses cough up lovely sharp
>>images.
>
> Hence the stampede by pros to obtain Canon's cheap kit lenses, right?

Cheap glass is slow. Not much use to pros.

>>Someone over at dpreview reports great results with the Canon 55-200
>>el-cheapo kit zoom for the Rebel. And the Tamron 28-75/2.8 is wonderful on
>>the 5D.
>
> Well, at least you don't hate aftermarket lenses.

Nope. Things like the Tokina 17/3.5, Sigma 12-24, Sigma 24/1.8 all have
their uses, especially on a FF camera.

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: SLR lens on DSLR's