# Effective reach 10 MP 1.3 x versus 8 MP 1.6 x

Wonder if the 10 MP 1.3 x MK III can make up the loss of reach with its bigger image size as compared to the 8 MP 1.6 x 30D. I generally photograph birds and wildlife.

regards,

Rajiv

The camera with the greater pixel density will be best when you have to crop the image.

But if you can get the perfect framing and composition with the higher resolution sensor then that would be best.

EG. if the bird takes up the entire 1.3x 10mp frame then you have a winner. but if you need to crop the image down to the 1.6x then you have just lost a lot of pixels.

The pixel density of the chips are roughly 25,000 pixels per square millimeter for the 30D and roughly 20,000 for the 1Dm3

I did the calculation a few months ago and I do not find my notes right now. But I remember the result.

Measured against pixel density the 1D Mk III has about 88-89% of "reach" compared to a 30D/20D/xt.

Tinu

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yes, pixel density is needed only when you are focal lenght limited.

crop factor of 1DIII against 30D is 0.89

check here : http://www.withinlights.com/Labo/Articles/CropFactor/index_us.php#RCF-calculator

But 1DIII has better AF (eh humm well, on paper at least) and better sensor tech, so you should get nearly same print quality.

Nicolas

Wait for the 1DsMkIII and you can have the same reach. You then have the advantage of more pixels in situations where you are not focal length limited.

This ignores the price factor of course !

Dave Peters

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Joe Kurkjian, Pbase Supporter

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i've seen yo post this alot but never really payed attention to what it's calculating on the last bold line.

can you explain what you are posting here and how a 21MP 1DSmk3 becomes "8.2 MP rating cropped to 30D".

wouldn't it be closer to 13mp cropped down?

or are you taking the actual 13mp remaining then adjusting it by some other factor?

J A K wrote:

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Joe Kurkjian, Pbase Supporter

chinch wrote:

i've seen yo post this alot but never really payed attention to what

it's calculating on the last bold line.can you explain what you are posting here and how a 21MP 1DSmk3

becomes "8.2 MP rating cropped to 30D".wouldn't it be closer to 13mp cropped down?

or are you taking the actual 13mp remaining then adjusting it by some

other factor?

Hi chinch:

I have no idea where you get "13mp" but anyway, if the 1DsIII is cropped down to the size of a 20D for example, both the horizontal and vertical dimensions of the 1DsIII are smaller by a factor of 1.6. Just take the ratio of the areas and calculate the new MP rating.

Regards,

Joe Kurkjian, Pbase Supporter

http://www.pbase.com/jkurkjia/original

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Hi chinch:

I have no idea where you get "13mp" but anyway, if the 1DsIII is

cropped down to the size of a 20D for example, both the horizontal

and vertical dimensions of the 1DsIII are smaller by a factor of 1.6.

Just take the ratio of the areas and calculate the new MP rating.Regards,

Joe Kurkjian, Pbase Supporter

thanks. i was doing the math wrong

is it accurate to extrapolate from that chart that the 40D crams in 2x the pixels into the equivalent size sensor as the 5D or 1DmkII?

5.0 vs 10.1

chinch wrote:

Hi chinch:

I have no idea where you get "13mp" but anyway, if the 1DsIII is

cropped down to the size of a 20D for example, both the horizontal

and vertical dimensions of the 1DsIII are smaller by a factor of 1.6.

Just take the ratio of the areas and calculate the new MP rating.Regards,

Joe Kurkjian, Pbase Supporterthanks. i was doing the math wrong

No sweat!

is it accurate to extrapolate from that chart that the 40D crams in

2x the pixels into the equivalent size sensor as the 5D or 1DmkII?5.0 vs 10.1

There is no need to extrapolate. All important metrics are in the table, look at the pixel pitch and multiply by the physical size of the sensor; if this is what you are after. I'm not sure exactly what you are after but the pixel pitch all by itself may be the answer the answer you are seeking.

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Joe Kurkjian, Pbase Supporter

http://www.pbase.com/jkurkjia/original

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"The Reach Factor" is the factor by which the focal length of one system needs to be scaled to match the number of pixels on the scene for the same perspective with another system. For example, 50mm with 20 MP would have the same reach as 100mm with 5 MP on the same format.

To answer the OP's question, then, the reach would be 13.5% greater for 1.6x at 8 MP than 1.3x (actually 1.26x) at 10 MP:

(1.6 / 1.26) * sqrt (8/10) = 1.135.

So, whatever FL you use on the 10 MP 1.6x system, you would use 1.135x that FL on the 8 MP 1.3x system, or, conversely, whatever FL you use on the 8 MP 1.3x system, you would use 0.88x (1/1.135) that FL on the 10 MP 1.6x system.

I got sick and tired of calculating that cr@p every time the subject came up in the forums and decided to make it available to everybody - to copy and use in their own responses.

Regards,

Joe Kurkjian, Pbase Supporter

http://www.pbase.com/jkurkjia/original

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Hi, Joe,

joe mama wrote:

"The Reach Factor" is the factor by which the focal length of one

system needs to be scaled to match the number of pixels on the scene

for the same perspective with another system. For example, 50mm with

20 MP would have the same reach as 100mm with 5 MP on the same format.

Gotcha. Thanks for the clear explanation.

Numerically, then, it is [proportional to] the inverse of the angle subtended by one pixel pitch.

I think our colleague Lee Jay had explained that to me a while ago, but I'm an old guy and forget stuff until I have had a chance to really work with it!

Best regards,

Doug

"The Reach Factor" is the factor by which the focal length of one

system needs to be scaled to match the number of pixels on the scene

for the same perspective with another system. For example, 50mm with

20 MP would have the same reach as 100mm with 5 MP on the same format.Gotcha. Thanks for the clear explanation.

Only too happy to oblige someone who knows a hundred times what I know about photography!

Numerically, then, it is [proportional to] the inverse of the angle

subtended by one pixel pitch.

That's clever! Didn't think of it that way!

I think our colleague Lee Jay had explained that to me a while ago,

but I'm an old guy and forget stuff until I have had a chance to

really work with it!

Lee Jay has taught me most of what I know in terms of the optics of photography, and he speaks no less highly of you.

Hi, Joe,

joe mama wrote:

Numerically, then, it is [proportional to] the inverse of the angle

subtended by one pixel pitch.That's clever! Didn't think of it that way!

It was Lee Jay who first articulated that notion to me.

In fact, one way to express a unit for it would be in pixels per radian.

In that case, the expression for reach would be:

R = f/p

where R is the reach (in pixels/radian), f is the focal length in mm, and p is the pixel pitch in mm.

The numbers we would often encounter would make the unit kilopixels per radian (kpx/rad) most useful.

Thus, on a camera with a pixel pitch of 5.7 um (such as the 40D, reckoned with respect to its largest output image), a lens with a focal length of 100 mm would give a reach of 17.5 kpx/rad.

Best regards,

Doug

Doug Kerr wrote:

R = f/p

where R is the reach (in pixels/radian), f is the focal length in mm,

and p is the pixel pitch in mm.The numbers we would often encounter would make the unit kilopixels

per radian (kpx/rad) most useful.Thus, on a camera with a pixel pitch of 5.7 um (such as the 40D,

reckoned with respect to its largest output image), a lens with a

focal length of 100 mm would give a reach of 17.5 kpx/rad.

Should we now call the unit for "reach" (kpx/rad) one kerr, one mama, or one leejay?

With a 400mm lens the picture angle on a 1.6 will be about that of a 640mm lens while on a Mark III it will be comparable to a 520mm lens, quite a difference. The image magnification will be the same for the 400mm regardless of whether it is mounted on a 40D, Mark III, or 5D.

The Mark III in theory will have faster AF and provide sharper images. In theory.

1DMKIII can indeed make the loss unless you have to constantly crop out huge amounts of picture. If I put 1.4x tele extender onto 500/4, I would have more autofocus performance and still better picture than with my ex. 30D with 500/4 only.

I cannot quite get pulse what is different with picture quality, no way i can prove it scientifically, but 1DMKIII just delivers that extra for pictures. Colors and color gradient are better. A good example is where blue sky is mixing into white cloud. I cannot rule out if this is caused by different sensor, pixel area per optics per mm, Digic III or whatever. Also noise is at least one stop better.

In the situation like the following: 1DMKIII and 500/4 + 1.4TC, I think I couldn't repeat color like that when I used 30D: