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Old Mar 15, 2010, 7:22 PM   #11
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Originally Posted by Chato View Post
The Mark II is the camera I had in mind for this comparison. Doing the math, my camera (Nikon D2x) has more pixels on target. Thus my decision to go ahead and buy that camera. But my statement also includes "all things being equal." And all things being equal the increased reach of a real telephoto as opposed to a cropped telephoto would show up if the match gave BOTH cameras the same amount of pixels on target. To do that the Mark II would have needed a 24 Meg sensor. And if the choice was between a full frame of 24 megs and my D2x, the ff camera would have a superior image.

Dave
I'm trying to follow this and a quick look at the maths shows the D2x having 181 pixels per mm on the sensor (4288 over 23.7mm), so to get that at 35mm, or 36mm x 24mm you would need 6516 x 4344 or 28.3mp. So the 24mp wouldn't quite do it but just over 28mp on a FF sensor would have the same pixel density as your D2x. I agree, if I could shoot with a 28mp FF camera over a 12mp APS-C then it would be the best all round option as I could crop in to the same size. However, with the current range of cameras it is possible to get higher resolution APS-C cameras and thus need vastly more pixels in FF for the same cropping ability.

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I don't know about your example below. The bottom image (number 4) compared to the third is so full of artifacts as to be almost unuseable.

Dave
In photo 4 you are not seeing artifacts from the camera but the printing process on the small globe which is more defined on certain colours. These are not picked as much up by the 3rd shot due to less pixels over the target although if you look at Libya then you can see it a little from the 5D.
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Old Mar 15, 2010, 9:06 PM   #12
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I'm trying to follow this and a quick look at the maths shows the D2x having 181 pixels per mm on the sensor (4288 over 23.7mm), so to get that at 35mm, or 36mm x 24mm you would need 6516 x 4344 or 28.3mp. So the 24mp wouldn't quite do it but just over 28mp on a FF sensor would have the same pixel density as your D2x. I agree, if I could shoot with a 28mp FF camera over a 12mp APS-C then it would be the best all round option as I could crop in to the same size. However, with the current range of cameras it is possible to get higher resolution APS-C cameras and thus need vastly more pixels in FF for the same cropping ability.



In photo 4 you are not seeing artifacts from the camera but the printing process on the small globe which is more defined on certain colours. These are not picked as much up by the 3rd shot due to less pixels over the target although if you look at Libya then you can see it a little from the 5D.
My bad about the numbers. I was quoting from memory when I was choosing between the Canon and the Nikon...

Look, let me make this simple. For arguments sake let us take 50mm as a base number; what the human eye sees (and yes I'm aware that the actual number is a few mm less).

With the Nikon and a 300 mm lens, with it's "450mm" you are getting a real magnification of six, with the Canon, and a 450mm lens you are getting a real magnification of nine; in terms of resolving power. The assumed magnification of the Nikon is "empty" magnification, even though you will have to crop the Canon, it still will resolve more detail (or it would if it had a few megs more). The Nikon it is true, has more pixels on target - Which is better than nothing - But it's still "empty" magnification.
The Resolving Power

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Old Mar 16, 2010, 11:05 AM   #13
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My bad about the numbers. I was quoting from memory when I was choosing between the Canon and the Nikon...

Look, let me make this simple. For arguments sake let us take 50mm as a base number; what the human eye sees (and yes I'm aware that the actual number is a few mm less).

With the Nikon and a 300 mm lens, with it's "450mm" you are getting a real magnification of six, with the Canon, and a 450mm lens you are getting a real magnification of nine; in terms of resolving power. The assumed magnification of the Nikon is "empty" magnification, even though you will have to crop the Canon, it still will resolve more detail (or it would if it had a few megs more). The Nikon it is true, has more pixels on target - Which is better than nothing - But it's still "empty" magnification.
The Resolving Power

Dave
Sorry Dave, I've totally lost what you are trying to say. The 6 times for Nikon and 9 times real magnification? I would have thought 450mm / 50mm = 9x on Nikon and with Canon and a 1.6 crop then 480mm / 50mm = 9.6x

Or are you talking about a FF Canon/Nikon/Sony, in which case the 300mm lens is 300mm and thus the magnification onto the sensor is 6x the perceived normal field of view.

Also for the empty magnification that is discussed in the pdf you linked to (interesting read and takes me back to my science degree days), this only comes into play when we reach the maximum resolving power of the lens (they are talking about 1000x magnification in the example), with the lenses and camera resolutions we are looking at then apart from very entry level glass you can still resolve full detail on the higher res sensors so this is tangible rather than empty magnification as was seen in my earlier examples.
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Old Mar 16, 2010, 1:12 PM   #14
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Sorry Dave, I've totally lost what you are trying to say. The 6 times for Nikon and 9 times real magnification? I would have thought 450mm / 50mm = 9x on Nikon and with Canon and a 1.6 crop then 480mm / 50mm = 9.6x

Or are you talking about a FF Canon/Nikon/Sony, in which case the 300mm lens is 300mm and thus the magnification onto the sensor is 6x the perceived normal field of view.

Also for the empty magnification that is discussed in the pdf you linked to (interesting read and takes me back to my science degree days), this only comes into play when we reach the maximum resolving power of the lens (they are talking about 1000x magnification in the example), with the lenses and camera resolutions we are looking at then apart from very entry level glass you can still resolve full detail on the higher res sensors so this is tangible rather than empty magnification as was seen in my earlier examples.
Empty magnification is exactly what the cropping factor accomplishes. They are using the example of mircroscopes, but it holds for any form of optical magnification. Simply increasing the size is Not an increase in resolution. The reason that the cropping factor has some value is because of the number of pixels on target -

Now for example, a 50mm lens, which because of a tiny sensor size might also be able to put more pixels on target. But let us say that the target was a basket ball. The 50mm lens might show a clear orange ball, and the true magnification might show a blurred ball with stripes and grain. So, the number of pixels will make that ball "clean," but it wont resolve the details.

Dave

Last edited by Chato; Mar 16, 2010 at 1:13 PM. Reason: typo (one of many)
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Old Mar 16, 2010, 4:27 PM   #15
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Default Is this the correct camera for bird taking

Thank you all so very much, I appreciated your help a lot. I thnk however that "Mole" gave me the answer I was looking for, he stated the difference between the Canon Powershot SX10 and the DSLR saying that ANY DSLR would be faster to respond then the SX10 to flighty birds. That is what I need. I have the slowness in my Nikon P3 digi, it is madeniing, I take a pic of something moving and by the time I click the shutter the picture has changed.

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Much very useful discussion here, just want to add my "2 cents" for what it's worth...
For a number of years I was the proud owner of a Canon Powershot S3IS (a predecessor of your SX10 IS), and tried to use it for bird photography. The lens reach was OK (especially for perched birds as Mark pointed out), but the shutter lag was a big problem. Most birds are so "flighty" that, between the time I pressed the shutter button and the time the camera acutally took the picture, the bird had moved somewhere else! I think that you will find that ANY digital SLR will be much faster to respond than is the SX10, and so you will miss far fewer pictures.
I have one more question if I may, the DSLR -A230L with the Lens does not mention if it has VR built in, does this mean that it does not have it or do I take for granted that it has the Vibration Reduction automatically?
Should I be o.k. with taking pictures without being afraid that the pics will come out "shaky"? Will I have to use the trypod exclusively with this camera? Thank you.

Calendula
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Old Mar 16, 2010, 7:05 PM   #16
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Thank you all so very much, I appreciated your help a lot. I thnk however that "Mole" gave me the answer I was looking for, he stated the difference between the Canon Powershot SX10 and the DSLR saying that ANY DSLR would be faster to respond then the SX10 to flighty birds. That is what I need. I have the slowness in my Nikon P3 digi, it is madeniing, I take a pic of something moving and by the time I click the shutter the picture has changed.



I have one more question if I may, the DSLR -A230L with the Lens does not mention if it has VR built in, does this mean that it does not have it or do I take for granted that it has the Vibration Reduction automatically?
Should I be o.k. with taking pictures without being afraid that the pics will come out "shaky"? Will I have to use the trypod exclusively with this camera? Thank you.

Calendula
Calendula, sorry for all the other ramblings that have gone on in this thread, glad you've got the information that you require.

The A230 has build in stabilisation so you don't need it in the lens

As for the blurred photos, needing a tripod, the stabilisation will help but can't do miracles so it will depend on the situation. If you are photographing something that is moving then you still need to have a fast shutter speed to freeze the movement, stabilisation can't assist with this, but for something that is not moving then you can get a sharp shot with a lower shutter speed than if you didn't have stabilisation. It's like everything in photography, it is a tool that can be helpful at the right time.
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Old Mar 16, 2010, 7:18 PM   #17
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Empty magnification is exactly what the cropping factor accomplishes. They are using the example of mircroscopes, but it holds for any form of optical magnification. Simply increasing the size is Not an increase in resolution. The reason that the cropping factor has some value is because of the number of pixels on target -

Now for example, a 50mm lens, which because of a tiny sensor size might also be able to put more pixels on target. But let us say that the target was a basket ball. The 50mm lens might show a clear orange ball, and the true magnification might show a blurred ball with stripes and grain. So, the number of pixels will make that ball "clean," but it wont resolve the details.

Dave
I wasn't going to reply as we are just going around in circles.

From the article you linked to,

"Furthermore the end
magnification should not be higher than
1000x the NA of the objective, because
then the image will be only enlarged but
no further resolution will be visible. This
is called empty magnification."

So empty magnification is the increasing in size of the image without being able to see any increased resolution/detail in the photo. Are you saying that you disagree with the photo samples I've included where the 7D with the smaller sensor (and less pixels) is showing more detail than the FF 5DmkII?

Even at 12mp on an APS-C camera you will get a more detailed shot, so I can't see any way that crop factor relates to the document you shared and certainly we don't have empty magnification.

However, there might be a point using poor glass where this is true as it just can't resolve the higher detail but most main stream lenses wouldn't fall into this category. Also, in the future the lenses on the market might be out resolved by the sensors but again this isn't evident in the cameras we are discussing here or my examples.
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Old Mar 16, 2010, 7:55 PM   #18
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I wasn't going to reply as we are just going around in circles.

From the article you linked to,

"Furthermore the end
magnification should not be higher than
1000x the NA of the objective, because
then the image will be only enlarged but
no further resolution will be visible. This
is called empty magnification."

So empty magnification is the increasing in size of the image without being able to see any increased resolution/detail in the photo. Are you saying that you disagree with the photo samples I've included where the 7D with the smaller sensor (and less pixels) is showing more detail than the FF 5DmkII?

Even at 12mp on an APS-C camera you will get a more detailed shot, so I can't see any way that crop factor relates to the document you shared and certainly we don't have empty magnification.

However, there might be a point using poor glass where this is true as it just can't resolve the higher detail but most main stream lenses wouldn't fall into this category. Also, in the future the lenses on the market might be out resolved by the sensors but again this isn't evident in the cameras we are discussing here or my examples.
This is a mathamatical formula that applies equally whether we are talking about 2x or 2000x.

In the dispute we are having it's a question of cropping vs non cropping. Or to put it another way, does my cropping an image on my monitor, and then interpolating it up to the previous size mean that I have increased the resolving power?

This is what occurs in the cropping factor of a DSLR. You are merely cropping the image, and that cropping is empty magnification.

If there are two objects very close together, but are not resolvable with a 300mm lens, but ARE resolvable with a 450mm lens, do you really think that cropping to achieve the angle of a 450mm lens will suddenly and magically resolve the two objects?

Unlike the various links I gave (and will give another again) the difference between 300mm and 450mm is relatively small - Nevertheless the difference is real.

Perhaps this link will make it clearer.
The Resolving Power of Telescopes

Again, my bad, this is my last post on the topic.

Dave

Last edited by Chato; Mar 16, 2010 at 7:56 PM. Reason: typo
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Old Mar 16, 2010, 8:15 PM   #19
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Originally Posted by Chato View Post
This is a mathamatical formula that applies equally whether we are talking about 2x or 2000x.

In the dispute we are having it's a question of cropping vs non cropping. Or to put it another way, does my cropping an image on my monitor, and then interpolating it up to the previous size mean that I have increased the resolving power?

This is what occurs in the cropping factor of a DSLR. You are merely cropping the image, and that cropping is empty magnification.

If there are two objects very close together, but are not resolvable with a 300mm lens, but ARE resolvable with a 450mm lens, do you really think that cropping to achieve the angle of a 450mm lens will suddenly and magically resolve the two objects?

Unlike the various links I gave (and will give another again) the difference between 300mm and 450mm is relatively small - Nevertheless the difference is real.

Perhaps this link will make it clearer.
The Resolving Power of Telescopes

Again, my bad, this is my last post on the topic.

Dave
We are not talking about interpolating, we are talking about using a crop sensor over a FF sensor, so even if we have the same number of pixels we have these pixels in a narrower field of view so yes there is a better resolution.

If you crop a screen grab this isn't the same situation at all as then you are just binning pixels and thus would be empty magnification. Throughout this thread and this discussion that came about when you said "The crop factor has some, but little impact on this question". The reach of the lens is key to the OP, be is with the 100mm (560mm equivalent) of the SX10 or the 450-480mm equivalent of a Nikon/Sony-Canon dSLR. If it were a Canon 5D then the 300mm lens wouldn't be nearly as effective as one of the APS-C cameras and even the 5DmkII doesn't have the resolution to win.

Again the theoretical information in the tread you posted is interesting, but still not what we are finding in the real world as again we are not at the limits of the lenses we are using. If we were putting 40mp on an APS-C sensor then likely there would be diminishing returns to the extra camera resolution.

If you want to leave the discussion there that is fine, but if you have anything else to share on this discussion please do. Posting some photos or something that is related to this exact situation rather than theoretical works that look at the limits of telephoto lenses which don't answer anything as we are not at the limits that would be helpful. I like most people here are keen to learn so if I've made an error in what I state or what I've observed in my photo tests then I would like to do so. If there is something that clearly counters what I posted with the 7D and 5DmkII showing the increased detail by having the crop camera so working with the narrower field of view is having a major impact.
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Old Mar 16, 2010, 8:40 PM   #20
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We are not talking about interpolating, we are talking about using a crop sensor over a FF sensor, so even if we have the same number of pixels we have these pixels in a narrower field of view so yes there is a better resolution.
Yes, we're not talking about interpolating, we're talking about "cropping," and no amount of cropping will resolve two objects that are too far away to be seperated by the empty magnification of changing the angle of view. Because you might wind up with more pixels on the target, merely means that you will still see only one object - it will simply be clearer than the same view uncropped.

Dave
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