7D versus Mark IV: Pixels per bird (1 Viewer)

Hirundapus · Nov 7, 2009

I'm struggling with the maths here. Can someone help me out please?
I'm trying to work out what the comparative 'pixels per bird' would be on a bird very small in the image (that's what most of my shots are!), say a bird that just fills the circle in the centre of the focussing screen, or smaller....
For comparative purposes, a 7D, if the resolution were compared to a full-frame sensor would be 1.6 x 18mp = 28.8mp, correct?
Whereas a Mark IV would be 1.3 x 16mp = 20.8mp, correct?
So a very small bird in the image in a 7D, covering say 288 pixels, would cover only 208 pixels in a Mark IV. Is that correct?
So the resolution/quality of the Mark IV pixels would need to be something like 40% better that those of the 7D to match it's image quality when it comes to very distant birds. Is that correct?
And if it is correct, is it likely that the Mark IV pixel quality could really be 40% or more better than the 7D, so it could produce a better image of distant birds?

Roy C · Nov 7, 2009

Hirundapus said:
For comparative purposes, a 7D, if the resolution were compared to a full-frame sensor would be 1.6 x 18mp = 28.8mp, correct?
Whereas a Mark IV would be 1.3 x 16mp = 20.8mp, correct?

Not sure this is correct, for instance:
The resolution of the 7D is 5184 x 3456 pixels so a full frame equivalent would be (5184 x 1.6) x (3456 x 1.6) = 45.8 MP

And for the 1.3 cropper:
(5184 x 1.3) x (3456 x 1.3) = 30 MP.

Hirundapus · Nov 7, 2009

I think that might be correct, thanks Roy, but then the difference between the two cameras pixels-per-bird for a small-in-the-image bird is even greater, so the 7D will surely aways be significantly better for distant birds?

tjsimonsen · Nov 7, 2009

Hirundapus said:
I think that might be correct, thanks Roy, but then the difference between the two cameras pixels-per-bird for a small-in-the-image bird is even greater, so the 7D will surely aways be significantly better for distant birds?

Only if you use the very best lenses.

Thomas

GYRob · Nov 7, 2009

i thnik the mk4 would have to be 30mp on the 1.3 crop to be the same BUT the 7d is 1.6 crop so the 7d would still win for mp s on the bird and by quite a long way too
500mm on a 1.3 crop = 650mm field of view
500mm on a 1.6crop = 800mm field of view
so your in effect getting 150mm more reach and 2 MPs more with the 7d over the mk4
thats why i have a 7d now

Rob

RazorTM · Nov 9, 2009

You don't really have to think about what the megapixel count would be "if this camera had a full frame sensor."

Just divide sensor area by megapixels to get what DPReview calls "pixel density." Higher pixel density = more pixels per duck, no matter what lens you use.

Pixel densities for Canon's big guns + the 7D are here:
http://www.dpreview.com/reviews/com...v,canon_eos1dsmkii,canon_eos1dsmkiii&show=all

The 7D has 5.4 MP/cm^2 and the 1DIV has 3.1 MP/cm^2.

Tim Taylor · Nov 9, 2009

That's a really interesting comparison page there. What an amazing pixel density on the 7D! If that translates into genuine extra detail I suspect that's the camera I'll go for.

Chris Galvin · Nov 9, 2009

Tim Taylor said:
That's a really interesting comparison page there. What an amazing pixel density on the 7D! If that translates into genuine extra detail I suspect that's the camera I'll go for.

Especially as it show my 1DIIn as having 1.9 :C:C

I had already decided on a 7D but this info helps

Roy C · Nov 9, 2009

I am not sure that pixel density is necessarily the be all as far as IQ goes - if that was so then some of the point and shoot jobs with minute sensors would be tops I suspect!.

hampers · Nov 9, 2009

Are the pixels on all the Canon range the same size and if not how does this affect the image quality. I can see the point of the discussion but why do pros use the lower pixel density cameras if the image detail is lower. Perhaps I just have an idealisitic view that the pros know best. Whichever I love my 1D and am happy with quality, plus af at f8. Would love to see the same photograph on 1 full frame, 1.3 and 1.6 sensors cropped to try and assess the difference. the 7D may have me wavering now.

Phil

Tim Taylor · Nov 9, 2009

As I understand it, the biggest things affecting image quality are proximity to the subject and the lens you use together with good lens support and exposing the subject correctly. Nice light and an attractive composition and then good processing are also hugely improtant. I think the pros such as Nigel Blake are excellent at getting all of these things right. For more 'casual' photographers getting more pixels over the subject can be achieved in part by having more pixels on the sensor. You still won't necessarily get the detail you want though without getting close as well.

That's my abbreviated and probably inaccurate understanding of this vast topic...LOL

Perhaps if Nigel is lurking somewhere he can set the record straight.

nigelblake · Nov 9, 2009

........... its all in here, read and digest, it isn't anywhere near as simple as relative pixel sizes when you take into account optics, divergence, circles of confususion etc etc!

http://www.clarkvision.com/imagedetail/does.pixel.size.matter/#Depth_of_Field_Myth

At the end of the day the camera is just a tool of the trade; If I had Tiger Woods Golf clubs I still coudn't hit a hole in one if I spent all day every day for weeks on end trying!

GYRob · Nov 9, 2009

hampers said:
Are the pixels on all the Canon range the same size and if not how does this affect the image quality. I can see the point of the discussion but why do pros use the lower pixel density cameras if the image detail is lower. Perhaps I just have an idealisitic view that the pros know best. Whichever I love my 1D and am happy with quality, plus af at f8. Would love to see the same photograph on 1 full frame, 1.3 and 1.6 sensors cropped to try and assess the difference. the 7D may have me wavering now.

Phil

would you indeed a guy did this to show it all.
Rob.

Neil-T · Nov 9, 2009

That kingfisher must have sat still for a very long time for him to get the exact same shot with all those cameras.

GYRob · Nov 9, 2009

Chrysophylax said:
That kingfisher must have sat still for a very long time for him to get the exact same shot with all those cameras.

i take it your joking ,he resized the same shot to show what you get from the diffrent crop cameras .
Rob.

Carpe_Diem · Nov 10, 2009

Fantastic and informative thread here.

I too had already decided on trading in my back up 350D to get the 7D. This will give me the 7D as a main body with the 40D as my back up. This thread has just made the decision not to get the 1D IV.

Thank you all very much.

Cheers.

Tim Taylor · Nov 10, 2009

Back to pixels per bird

Sorry, gone off topic a bit here. If I understand it correctly, assuming you had a 7D and a 1D MkIV both with the same lenses the same distance from a bird, the ratio of pixels per bird 7D to MkIV would be:

ratio of crop factors x ratio of pixel densities
1.6/1.3 x 5.4/3.1 = 2.14

ie the 7D would have 2.14 x as many pixels on the bird as the 1D mkIV.

To compare your own current camera with either of these new models simply substitute your own camera crop ratios and pixel densities so for Chris Galvin and me with 1D MkIIs compared with a 7D:

1.3/1.3 x 5.4/1.5 = 3.6 x as many pixels per bird on the 7D as on the 1D mkII

Hope this is right!

RazorTM · Nov 10, 2009

Tim Taylor, I think you can ignore the sensor size if you are using the pixel density value that I introduced earlier. Using the same lens at the same distance on both cameras means that the image of the bird projected onto the sensor will also be the same size. If the projected image of the bird covers a 1cm^2 area on both sensors, then within that physical area on the sensor lies 5.4 megapixels on the 7D and 3.1 megapixels on the 1DIV.

Simply take 5.4/3.1 if comparing the 7D to the 1DIV and you get 1.74 times the number of pixels per bird.

RazorTM · Nov 10, 2009

Roy C said:
I am not sure that pixel density is necessarily the be all as far as IQ goes - if that was so then some of the point and shoot jobs with minute sensors would be tops I suspect!.

You're right, Roy. Higher pixel density increases resolution for the most part, but also brings about many unwanted side effects, like higher noise.

The article that Nigel posted is very informative!

Tim Taylor · Nov 10, 2009

RazorTM said:
Tim Taylor, I think you can ignore the sensor size if you are using the pixel density value that I introduced earlier. Using the same lens at the same distance on both cameras means that the image of the bird projected onto the sensor will also be the same size. If the projected image of the bird covers a 1cm^2 area on both sensors, then within that physical area on the sensor lies 5.4 megapixels on the 7D and 3.1 megapixels on the 1DIV.

Simply take 5.4/3.1 if comparing the 7D to the 1DIV and you get 1.74 times the number of pixels per bird.

I'm sure you're right. Why do I always find this crop factor so confusing?!

7D versus Mark IV: Pixels per bird (1 Viewer)

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