# If I Cropped A Photo From A 5D...

Discussion in 'Digital Photography' started by Mike, Jun 28, 2006.

1. ### MikeGuest

I never was any good at maths.

If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
megapixels would the image be?

5D Sensor Size = 36 x 24 mm
5D Resolution = 4368 x 2912

20D Sensor Size = 22.5 x 15.0 mm
20D Resolution = 3504 x 2336

Mike, Jun 28, 2006

2. ### Daniel SilevitchGuest

On Wed, 28 Jun 2006 21:01:29 +0100, Mike <> wrote:
> I never was any good at maths.
>
> If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
> megapixels would the image be?
>
> 5D Sensor Size = 36 x 24 mm
> 5D Resolution = 4368 x 2912

cropped 5D: (4368/1.6)*(2912/1.6) = 4,968,600
or roughly 5 megapixels.

-dms

Daniel Silevitch, Jun 28, 2006

3. ### PrometheusGuest

In article <>, Mike
<> writes
>I never was any good at maths.
>
>If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
>megapixels would the image be?
>
>5D Sensor Size = 36 x 24 mm
>5D Resolution = 4368 x 2912

>20D Sensor Size = 22.5 x 15.0 mm
>20D Resolution = 3504 x 2336

(4368/1.6) * (2912/1.6) = 4,968,600

3504 * 2336 = 8,185,344
--
Ian G8ILZ

Prometheus, Jun 28, 2006
4. ### MikeGuest

Cheers Daniel

"Daniel Silevitch" <> wrote in message
news:...
> On Wed, 28 Jun 2006 21:01:29 +0100, Mike <> wrote:
>> I never was any good at maths.
>>
>> If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
>> megapixels would the image be?
>>
>> 5D Sensor Size = 36 x 24 mm
>> 5D Resolution = 4368 x 2912

>
> cropped 5D: (4368/1.6)*(2912/1.6) = 4,968,600
> or roughly 5 megapixels.
>
> -dms
>

Mike, Jun 28, 2006
5. ### boozzGuest

Mike wrote:
> I never was any good at maths.
>
> If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
> megapixels would the image be?
>
> 5D Sensor Size = 36 x 24 mm
> 5D Resolution = 4368 x 2912
>
> 20D Sensor Size = 22.5 x 15.0 mm
> 20D Resolution = 3504 x 2336

boozz, Jun 29, 2006
6. ### David J. LittleboyGuest

"Mike" <> wrote:
>I never was any good at maths.

The only difficulty is that people sometimes forget to divide by 1.6 in
_both_ directions.

> If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
> megapixels would the image be?
>
> 5D Sensor Size = 36 x 24 mm
> 5D Resolution = 4368 x 2912
>
> 20D Sensor Size = 22.5 x 15.0 mm
> 20D Resolution = 3504 x 2336

1.6x cropped 5D resolution = (4368/1.6) x (2912/1.6) = 2730 x 1822 = 4.9 MP.

Since the 5D pixels are quite a bit larger than 20D pixels, if you use the
same area of sensor from the 5D as you use on the 20D, you get a lot fewer
pixels.

In other words, if most of your shooting is birds with long lenses
(especially if you crop most of your shots), you really don't want a 5D.

The only exception would be if you really wanted more pixels on the birds
(to make larger prints) and were willing to use much bigger glass. But most
birders, I'd think, would be using the largest lenses they can afford...

David J. Littleboy
Tokyo, Japan

David J. Littleboy, Jun 29, 2006
7. ### Roy GGuest

"Mike" <> wrote in message
news:...
>I never was any good at maths.
>
> If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
> megapixels would the image be?
>
> 5D Sensor Size = 36 x 24 mm
> 5D Resolution = 4368 x 2912
>
> 20D Sensor Size = 22.5 x 15.0 mm
> 20D Resolution = 3504 x 2336
>
>

Hi.

You should have paid a bit more attention at school, if you really cannot
work out this answer for yourself.

There is quite a lot of Arithmetic involved in Photography, and in every day
life. You might well be paying too much for things you buy, or not getting
paid enough for the work you do, or even worse paying too much in taxes.

If you came to stay at my Guesthouse for 10 nights, and I said that my
special offer of "7 Nights for the price of 6" would be applied, would you
know whether I charged the correct amount. Perhaps I should do you a
special offer of "6 for the price of 7"

Roy G

Roy G, Jun 29, 2006
8. ### John McWilliamsGuest

On 6/29/06 6:33 AM, Roy G posted the following:
>
> If you came to stay at my Guesthouse for 10 nights, and I said that my
> special offer of "7 Nights for the price of 6" would be applied, would you
> know whether I charged the correct amount. Perhaps I should do you a
> special offer of "6 for the price of 7"
>

I'd be especially wary of how the remaining 3 -or 4 - nights were
charged! Would they be charged reg. rates, or 6/7ths, or 7/6ths??
Enquiring minds and all.

--
john mcwilliams

John McWilliams, Jun 29, 2006
9. ### Roy GGuest

"John McWilliams" <> wrote in message
news:...
> On 6/29/06 6:33 AM, Roy G posted the following:
>>
>> If you came to stay at my Guesthouse for 10 nights, and I said that my
>> special offer of "7 Nights for the price of 6" would be applied, would
>> you know whether I charged the correct amount. Perhaps I should do you a
>> special offer of "6 for the price of 7"
>>

> I'd be especially wary of how the remaining 3 -or 4 - nights were charged!
> Would they be charged reg. rates, or 6/7ths, or 7/6ths?? Enquiring minds
> and all.
>
> --
> john mcwilliams

Ah, but you are not the arithmetically challenged poster who could not work
out how many pixels.

If the booking were to be initiated through this NG, you might well get an
even better deal.

But then again..............................

Roy G

Roy G, Jun 29, 2006
10. ### Matt IonGuest

Roy G wrote:
> "Mike" <> wrote in message
> news:...
>
>>I never was any good at maths.
>>
>>If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
>>megapixels would the image be?
>>
>>5D Sensor Size = 36 x 24 mm
>>5D Resolution = 4368 x 2912
>>
>>20D Sensor Size = 22.5 x 15.0 mm
>>20D Resolution = 3504 x 2336
>>
>>

>
> Hi.
>
> You should have paid a bit more attention at school, if you really cannot
> work out this answer for yourself.
>
> There is quite a lot of Arithmetic involved in Photography, and in every day
> life. You might well be paying too much for things you buy, or not getting
> paid enough for the work you do, or even worse paying too much in taxes.

Maybe the math itself isn't the problem... everyone else who's responded
seems to have a grasp on how to work their calculators, but my
understanding was that the "crop factor" figure referred to the effectiv
35mm focal length; ie. a 200mm lens on a 1.6 "crop factor" sensor would
be equivalent to a (200*1.6) or 320mm lens on a 35mm sensor; on a 1.5
"crop factor" sensor, it would be (200*1.5)=300mm.

If that is in fact the case, then all the other calculations provided
thus far are wrong...

Matt Ion, Jun 29, 2006
11. ### John McWilliamsGuest

On 6/29/06 8:34 AM, Roy G posted the following:
> "John McWilliams" <> wrote in message
> news:...
>> On 6/29/06 6:33 AM, Roy G posted the following:
>>> If you came to stay at my Guesthouse for 10 nights, and I said that my
>>> special offer of "7 Nights for the price of 6" would be applied, would
>>> you know whether I charged the correct amount. Perhaps I should do you a
>>> special offer of "6 for the price of 7"
>>>

>> I'd be especially wary of how the remaining 3 -or 4 - nights were charged!
>> Would they be charged reg. rates, or 6/7ths, or 7/6ths?? Enquiring minds
>> and all.
>>
>> --
>> john mcwilliams

>
> Ah, but you are not the arithmetically challenged poster who could not work
> out how many pixels.
>
> If the booking were to be initiated through this NG, you might well get an
> even better deal.
>
> But then again..............................
>

All righty, then, gotta web page?

--
john mcwilliams

John McWilliams, Jun 29, 2006
12. ### Eric MillerGuest

"Matt Ion" <> wrote in message
news:SBSog.109025\$IK3.103979@pd7tw1no...
> Roy G wrote:
>> "Mike" <> wrote in message
>> news:...
>>
>>>I never was any good at maths.
>>>
>>>If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
>>>megapixels would the image be?
>>>
>>>5D Sensor Size = 36 x 24 mm
>>>5D Resolution = 4368 x 2912
>>>
>>>20D Sensor Size = 22.5 x 15.0 mm
>>>20D Resolution = 3504 x 2336
>>>
>>>

>>
>> Hi.
>>
>> You should have paid a bit more attention at school, if you really cannot
>> work out this answer for yourself.
>>
>> There is quite a lot of Arithmetic involved in Photography, and in every
>> day life. You might well be paying too much for things you buy, or not
>> getting paid enough for the work you do, or even worse paying too much in
>> taxes.

>
> Maybe the math itself isn't the problem... everyone else who's responded
> seems to have a grasp on how to work their calculators, but my
> understanding was that the "crop factor" figure referred to the effectiv
> 35mm focal length; ie. a 200mm lens on a 1.6 "crop factor" sensor would be
> equivalent to a (200*1.6) or 320mm lens on a 35mm sensor; on a 1.5 "crop
> factor" sensor, it would be (200*1.5)=300mm.
>
> If that is in fact the case, then all the other calculations provided thus
> far are wrong...

Using a 20D, whose sensor is 22.5 x 15.0mm, as an example, where
"full-size" 35mm is 24 x 36mm, 1.6 x 22.5 = 36 and 1.6 x 15 = 24. So the
length and width of the APS-C of the 20D are each 1/1.6 of same dimension
of a full size sensor. So all the calculations so far are pretty much
correct. What numbers did you come up with?

Eric Miller

Eric Miller, Jun 29, 2006
13. ### MattGuest

Don't be so ridiculous.

Making such a ridiculous statement gives me the impression that you are one
of those people who take photos of brick walls and colour charts to see how
good camera equipment is, as opposed to actually getting amongst the action
and getting great photos. It wouldn't surprise me if you have never even
photographed anything outside of the UK.

"Roy G" <> wrote in message
news:_EQog.82604\$...
>
> You should have paid a bit more attention at school, if you really cannot
> work out this answer for yourself.
>
> There is quite a lot of Arithmetic involved in Photography, and in every
> day life. You might well be paying too much for things you buy, or not
> getting paid enough for the work you do, or even worse paying too much in
> taxes.
>
> If you came to stay at my Guesthouse for 10 nights, and I said that my
> special offer of "7 Nights for the price of 6" would be applied, would
> you know whether I charged the correct amount. Perhaps I should do you a
> special offer of "6 for the price of 7"
>
> Roy G
>

Matt, Jun 29, 2006
14. ### Bill HiltonGuest

>Matt Ion wrote:
>
> If that is in fact the case, then all the other calculations provided
> thus far are wrong...

Maybe you are confusing linear with area? If it's 1.6 each direction
then it's 2.56 area-wise. Multiply the cropped pixel number by 2.56
and you'll see it's correct.

Bill

Bill Hilton, Jun 29, 2006
15. ### PrometheusGuest

In article <>, Bill
Hilton <> writes
>
>>Matt Ion wrote:
>>
>> If that is in fact the case, then all the other calculations provided
>> thus far are wrong...

>
>Maybe you are confusing linear with area? If it's 1.6 each direction
>then it's 2.56 area-wise. Multiply the cropped pixel number by 2.56
>and you'll see it's correct.

Hence my post in which I put "(4368/1.6) * (2912/1.6) = 4,968,600" I did
consider (4368 * 29120 / 1.6^2 = 4,968,600, but felt that the poster
would not comprehend the derivation.

--
Ian G8ILZ

Prometheus, Jun 29, 2006
16. ### Matt IonGuest

Bill Hilton wrote:
>>Matt Ion wrote:
>>
>>If that is in fact the case, then all the other calculations provided
>>thus far are wrong...

>
>
> Maybe you are confusing linear with area? If it's 1.6 each direction
> then it's 2.56 area-wise. Multiply the cropped pixel number by 2.56
> and you'll see it's correct.

Umm no, we're talking about two different things... everyone else here
is calculating the difference in sensor size... my understanding was the
"crop factor" number was a relative difference in "35mm equivalent focal
length".

My point was, if the number does refer to the "35mm equivalent focal
length", then any calculations against the sensor size are going to be
necessarily wrong.

Matt Ion, Jun 30, 2006
17. ### Matt IonGuest

Prometheus wrote:
> In article <>, Bill
> Hilton <> writes
>
>>
>>> Matt Ion wrote:
>>>
>>> If that is in fact the case, then all the other calculations provided
>>> thus far are wrong...

>>
>>
>> Maybe you are confusing linear with area? If it's 1.6 each direction
>> then it's 2.56 area-wise. Multiply the cropped pixel number by 2.56
>> and you'll see it's correct.

>
>
> Hence my post in which I put "(4368/1.6) * (2912/1.6) = 4,968,600" I did
> consider (4368 * 29120 / 1.6^2 = 4,968,600, but felt that the poster
> would not comprehend the derivation.

But that's meaningless - "crop factor" numbers are published to indicate
the difference in field of view you'll get compared to a 35mm film
frame. The number of pixels one way or the other doesn't tell you that,
particularly since 35mm film doesn't have pixels, and the size of the
pixels varies from one camera (sensor) to the next. It's a useless
specification that way.

This, I believe, is the best explanation of "crop factor" that I've come
across so far:
http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml

In particular:
"The focal length remains the exact same but the angle of view is
reduced to the same as that of a lens of 1.5 or 1.6 times greater focal
length on a 35mm format camera."

Matt Ion, Jun 30, 2006
18. ### David J. LittleboyGuest

"Matt Ion" <> wrote:
>> "Mike" <> wrote in message
>>>
>>>If I cropped a photo from a 5D to match a 1.6 crop sensor size, how many
>>>megapixels would the image be?

>
> Maybe the math itself isn't the problem... everyone else who's responded
> seems to have a grasp on how to work their calculators, but my
> understanding was that the "crop factor" figure referred to the effectiv
> 35mm focal length; ie. a 200mm lens on a 1.6 "crop factor" sensor would be
> equivalent to a (200*1.6) or 320mm lens on a 35mm sensor; on a 1.5 "crop
> factor" sensor, it would be (200*1.5)=300mm.

No. The "crop factor" figure refers to the ratio of the sizes of the
formats.

This discussion is about using a crop from the 5D to get the same angle of
view as a 20D user would get using the full 20D sensor. The only question
here is how many pixels would one get if one used the same focal length
lenses on a 5D and a 20D from the same position and cropped the 5D image to
get the same image content as the 20D image.

This discussion has nothing to do with focal lengths.

> If that is in fact the case, then all the other calculations provided thus
> far are wrong...

Nope, everyone so far is exactly right.

David J. Littleboy
Tokyo, Japan

David J. Littleboy, Jun 30, 2006
19. ### Bill HiltonGuest

>> Bill Hilton wrote:
>> Maybe you are confusing linear with area? If it's 1.6 each direction
>> then it's 2.56 area-wise. Multiply the cropped pixel number by 2.56
>> and you'll see it's correct.

>Matt Ion replied
>
> Umm no, we're talking about two different things... everyone else here
> is calculating the difference in sensor size...

That was what the original poster asked for ... "If I cropped a photo
from a 5D to match a 1.6 crop sensor size, how many megapixels would
the image be?"

The number that was calculated, just under 5 Mpixels, follows from that
Q.

>my understanding was the "crop factor" number was a relative difference
>in "35mm equivalent focal length".

Yes, because of the difference in sensor size. So?

> My point was, if the number does refer to the "35mm equivalent focal
> length", then any calculations against the sensor size are going to be
> necessarily wrong.

So what number to YOU come up with to answer his question, a number
that addresses your concerns? I don't really see the point you are
trying to make, sorry ...

Bill

Bill Hilton, Jun 30, 2006
20. ### ASAARGuest

On Fri, 30 Jun 2006 00:08:28 GMT, Matt Ion wrote:

> My point was, if the number does refer to the "35mm equivalent focal
> length", then any calculations against the sensor size are going to be
> necessarily wrong.

The 35mm equivalent focal length doesn't come into play at all,
because the reference to "1.6 crop sensor size" was just an another
way of specifying the dimensions of the 20D's sensor, which was in
fact already known by the OP.

Just a little basic math shows that the sensors of the 5D and 20D
have, respectively, 36x24 sq. mm and 22.5x15.0 sq. mm, or 865 sq. mm
vs 337.5 sq.mm. From this, if you wanted to know how many of the
5D's 12 megapixels would be covered by placing a 20D sensor over the
5D's sensor, it would be:

Pixel Count == 12 mp * 337.5 / 865 == 4.74 mp, which agrees with
DS's "roughly 5 megapixels", P's "4,968,600", DJL's "4.9 MP", who
also said "This discussion has nothing to do with focal lengths".

The 4.74 mp (4,968,600 pixels) result is a bit off, as the 5D's
sensor is, I think, slightly greater than 12 mp, but it's close
enough for gov't work.

--
"What's lens got to do with it?" -- Tina Turner

ASAAR, Jun 30, 2006