Answer this one question!

[Eugene Powers]

That is right, crop sensor does not see all of the last element in FF lens but it does see all of the last element on crop factor lenses designed only for these cameras. Notice something else, everything smaller in crop factor cameras not only the sensor, like mirror and the prism for example. The only thing not smaller is the mount and only because OM did not want to create new mount so we can use all of their lenses. Also look at MTF charts for crop lenses, they don't have as much data (truncated) on them.

--
Eugene

The only time a smaller sensor with the same pixel count is superior to a larger sensor (aka higher pixel density) is when you are focal-length limited.

Lee Jay

 

[joe mama]

original point of testing corner sharpness between crop camera and FF.
If you want to test FOV, DOV, noise and everything else you can use
whatever you want or have. But for the original test to determine
if crop camera suffers as much as FF camera you need to eliminate
all of the variables and different lenses are variables.

...to compare corner sharpness between the two formats for equivalent images. I mean, for me, personally, I see no point in comparing images that are not equivalent, except if you are comparing them from an artisitic point of view, such as the more shallow DOF of the FF image compared to the 1.6x image, but that was not the point here.

For example, if you are comparing the 135 / 2L to the 70-200 / 2.8L, both on the same camera, and they were the same sharpness wide open, would you then say that the 70-200 / 2.8L is just as sharp as the 135 / 2L? Or would you compare them both at f / 2.8 (again, if using them both on the same camera)? To me, it's quite obvious: you would compare them at the same f-ratio (and once again, if they are both being used by the same camera -- I just need to hammer this point since the rest of the thread was not using the same camera).

Likewise, if I am comparing the 135 / 2L on the 5D to the 85 / 1.2L on the 30D, I would compare them both wide open, or at any pairing of f-ratios 1 1/3 stops apart, since that is what would produce an equivalent image.

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

 

[joe mama]

if you taking picture of the continuous object like a brick wall.

...for pics of objects similar to brick walls. Is that useful?

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

 

[Eugene Powers]

original point of testing corner sharpness between crop camera and FF.
If you want to test FOV, DOV, noise and everything else you can use
whatever you want or have. But for the original test to determine
if crop camera suffers as much as FF camera you need to eliminate
all of the variables and different lenses are variables.

...to compare corner sharpness between the two formats for
equivalent images. I mean, for me, personally, I see no point in
comparing images that are not equivalent, except if you are
comparing them from an artisitic point of view, such as the more
shallow DOF of the FF image compared to the 1.6x image, but that
was not the point here.

For example, if you are comparing the 135 / 2L to the 70-200 /
2.8L, both on the same camera, and they were the same sharpness
wide open, would you then say that the 70-200 / 2.8L is just as
sharp as the 135 / 2L? Or would you compare them both at f / 2.8
(again, if using them both on the same camera)? To me, it's quite
obvious: you would compare them at the same f-ratio (and once
again, if they are both being used by the same camera -- I just
need to hammer this point since the rest of the thread was not
using the same camera).

Technically you can compare anything with the same name in it.

You can compare Ferrari to Volvo if you want. Would it be fare comparison? Depends on your point of view and what you are trying to achieve.

The way I would test these two lenses I would use only one camera to be fair and I would try to match focal length with aperture setting to eliminate all of the variables. So I would set 70-200mm at 135mm with corresponding aperture. I would do it at F2.8, F4, F5.6, F8 and F11.
Test is done.

Likewise, if I am comparing the 135 / 2L on the 5D to the 85 / 1.2L
on the 30D, I would compare them both wide open, or at any pairing
of f-ratios 1 1/3 stops apart, since that is what would produce an
equivalent image.

I would consider this an unfair test to the lenses used and to the cameras because they are all different. But it might be fair test as a system only if you use it as a system. It's like comparing two Point and Shoot systems let's say Canon S5 IS and Panasonic DMC-FZ30. They both have almost everything the same.

Since you can use different lenses on both cameras it is not really the system but only the system you defined. In this case you would have to test every possible combination of lenses and those two cameras to be fair. You would have to use Canon, Sigma and Tamron lenses too.

Don't you think it would be easier my way by eliminating DOF, FOV, noise, lenses and every other possible variable to test for corner sharpness?

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my
photos. If you wish to use any of my photos for any purpose other
than editing in these forums, please ask.

--
Eugene

The only time a smaller sensor with the same pixel count is superior to a larger sensor (aka higher pixel density) is when you are focal-length limited.

Lee Jay

 

[Eugene Powers]

YES, to me it would be for this particular test. I want to make it clear that original discussion was corner sharpness on both formats and nothing else.

Original tester was using books so you did not have any problem with that so why do you have problem with a brick wall?

--
Eugene

The only time a smaller sensor with the same pixel count is superior to a larger sensor (aka higher pixel density) is when you are focal-length limited.

Lee Jay

 

[Amin Sabet]

... relaxing the constraints on
optical quality by eliminating the need for them to be sharp to the
edges of the 35mm frame.

If they don't have to be sharp to the edges of the 35mm frame to be
sharp to the edges of a crop frame, then the crop frame must not be
seeing all the glass.

No, that doesn't follow.

Seems to me that it does.

--
http://aminphoto.blogspot.com

 

[joe mama]

Technically you can compare anything with the same name in it.
You can compare Ferrari to Volvo if you want. Would it be fair
comparison? Depends on your point of view and what you are trying
to achieve.

Of course. We are debating what is fair and useful, and what you wish to achieve, not what you can compare. You can, in fact, compare apples and oranges -- I like oranges better. : )

The way I would test these two lenses I would use only one camera
to be fair and I would try to match focal length with aperture
setting to eliminate all of the variables. So I would set 70-200mm
at 135mm with corresponding aperture. I would do it at F2.8, F4,
F5.6, F8 and F11.
Test is done.

I agree. The reason for this is because the same FL has the same FOV, and the same aperture has the same DOF. So, when comparing lenses on cameras with different size sensors, once again, I would compare the same FOV and DOF.

Likewise, if I am comparing the 135 / 2L on the 5D to the 85 / 1.2L
on the 30D, I would compare them both wide open, or at any pairing
of f-ratios 1 1/3 stops apart, since that is what would produce an
equivalent image.

I would consider this an unfair test to the lenses used and to the
cameras because they are all different. But it might be fair test
as a system only if you use it as a system.

Now you understand what I am trying to say! I am not comparing cameras or lenses, I am comparing systems !

It's like comparing two Point and Shoot systems let's say Canon S5 IS
and Panasonic DMC-FZ30. They both have almost everything the same.
Since you can use different lenses on both cameras it is not really
the system but only the system you defined. In this case you would
have to test every possible combination of lenses and those two
cameras to be fair. You would have to use Canon, Sigma and Tamron
lenses too.

Again, I totally agree -- for a complete test. And you would have to state the limitations, as well. For example, in another thread I'm participating in, a person was considering moving from the 30D and 24-70 / 2.8L to the 5D. Well, a 24-70 / 2.8L on a 30D corresponds to a 38-112 / 4.5L on a 5D. No such lens exists. The closest is the 24-105 / 4L IS. Thus, I would use that as the basis of the comparison. But they are not equivalent, just the closest you can get with existing lenses.

So, I think we finally see eye to eye on this. Yes? : )

--
--joe

http://www.josephjamesphotography.com
http://www.pbase.com/joemama/

Please feel free to criticize, make suggestions, and edit my photos. If you wish to use any of my photos for any purpose other than editing in these forums, please ask.

 

[Lee Jay]

... relaxing the constraints on
optical quality by eliminating the need for them to be sharp to the
edges of the 35mm frame.

If they don't have to be sharp to the edges of the 35mm frame to be
sharp to the edges of a crop frame, then the crop frame must not be
seeing all the glass.

No, that doesn't follow.

Seems to me that it does.

Do you know how a lens works?

The light from a single point on the object (a small area equal to the are a pixel sees, actually) illuminates the entire lens aperture, which then focuses that light back to a single pixel.

http://en.wikipedia.org/wiki/Image:Lens3.svg

--
Lee Jay
(see profile for equipment)

 

[Amin Sabet]

I was mistaken about crop sensors not seeing all the glass. However, my understanding was that digital sensors were significantly less sensitive to non-parallel incident light. If that is true, one can conclude that a crop sensor will not use the edges of the lens as much as a FF sensor would.

--
http://aminphoto.blogspot.com

 

[Lee Jay]

I was mistaken about crop sensors not seeing all the glass.
However, my understanding was that digital sensors were
significantly less sensitive to non-parallel incident light. If
that is true, one can conclude that a crop sensor will not use the
edges of the lens as much as a FF sensor would.

I've done a bit of testing with my 5D and my film SLR, and I really don't see the difference I'd expect to see if the 5D's sensor were significantly less sensitive to off-axis light than is film. Certainly, the basic sensor is, but the microlenses seem to do a really good job of mitigating that effect for the sensor.

I really need to do a controlled test, but I haven't gotten around to it yet. But do you see much difference here (top right corner is the best for comparison)? Forget the bottom corners, they're in the shade of the tree and of the house in the bottom image.



--
Lee Jay
(see profile for equipment)