Crop Factor

On Mon, 11 May 2009 14:08:09 -0700 (PDT), dohc46 wrote:

After reading review after review after review 1 main question keeps
arising in my head.....what are they talking about:
"cropped my photo xxx%"
When I think of cropping, here is the extent of my knowledge.......

I look at my daughter somewhere towards the middle of the photo and
too far for my liking (she looks to small) and then the next think i
notice is, "darn it Aunt Ethel how did you get in the photo to the
left", & "darn it Fido why are you in the picture to the right peeing"
& "I wish I could bring my daughter closer"........AHHHHH I know the
answer....

I then proceed to grab the lasso or square line or whatever says crop
on my software, I put it around my daughter and then hit
apply......BOOM magic: she is closer/bigger, dog is gone & auntie is
gone.....that is my extent of cropping.

What are people talking about when they say, "my picture is cropped
100%", "my picture is cropped xxx%"....when I do my cropping there is
no % number popping up anywhere.....so how do they know what % is
being cropped..........

Probably a bad guess, I'll admit......but could it be that the
original photo was (example) 5 megabytes then after cropping it is now
only 2.5 megabytes.....would that be considered 100% cropping?

There are a few meanings to crop factor or percentage.

One is the crop factor required to match a digital cameras' small sensor to the
size of 35mm film. In this case, the crop factor is merely the percentage needed
by a particular camera, and YOU don't have to crop anything or worry about it
The usual crop factor is 1.5, which means that if you use a 50mm lens it becomes
equal to a 75mm lens on the other camera, (50 x 1.5 = 75). Note that the digital
sized lens would create a cropped image if used on the larger camera because it
can't throw as large an image on the film as it does on the small sensor. The
small sensor camera however makes perfect use of the smaller image, and
therefore the lens appears bigger. Nothing to worry about!

Another use of percentage of cropping applies to people cropping out a small
piece of the image but not re-sizing it. So if you take a 640 x 800 pixel piece
of a 3000 x 2000 pixel image and Email it to someone, you have sent them a 100%
crop of the image. They really mean 100% size... of the piece. If you cropped it
and resized it smaller, you might say it's a 50% crop if you re-sized it 50%,
but the actual crop percentage size is unknown! (Unless you do the math and
back-track...) The word crop here means 'piece'.

As for a percentage crop by itself, you would usually go by dimension, so a 50%
crop of a 1000 x 1000 size image would be 500 x 500. Note that the area here is
actually 25%, so it is possible for someone to say that it IS a 25% crop by
area. Also in this case there would be no such thing as 100% crop... it's like
dividing by zero.... "I made this 200x200 a 200x200, 100% crop"... I did
nothing!

Ain't language fun?

wrote in message
...
On Mon, 11 May 2009 14:08:09 -0700 (PDT), dohc46
wrote:

After reading review after review after review 1 main question keeps
arising in my head.....what are they talking about:
"cropped my photo xxx%"
When I think of cropping, here is the extent of my knowledge.......

I look at my daughter somewhere towards the middle of the photo and
too far for my liking (she looks to small) and then the next think i
notice is, "darn it Aunt Ethel how did you get in the photo to the
left", & "darn it Fido why are you in the picture to the right peeing"
& "I wish I could bring my daughter closer"........AHHHHH I know the
answer....

I then proceed to grab the lasso or square line or whatever says crop
on my software, I put it around my daughter and then hit
apply......BOOM magic: she is closer/bigger, dog is gone & auntie is
gone.....that is my extent of cropping.

What are people talking about when they say, "my picture is cropped
100%", "my picture is cropped xxx%"....when I do my cropping there is
no % number popping up anywhere.....so how do they know what % is
being cropped..........

Probably a bad guess, I'll admit......but could it be that the
original photo was (example) 5 megabytes then after cropping it is now
only 2.5 megabytes.....would that be considered 100% cropping?

There are a few meanings to crop factor or percentage.

One is the crop factor required to match a digital cameras' small sensor
to the
size of 35mm film. In this case, the crop factor is merely the percentage
needed
by a particular camera, and YOU don't have to crop anything or worry about
it
The usual crop factor is 1.5, which means that if you use a 50mm lens it
becomes
equal to a 75mm lens on the other camera, (50 x 1.5 = 75). Note that the
digital
sized lens would create a cropped image if used on the larger camera
because it
can't throw as large an image on the film as it does on the small sensor.
The
small sensor camera however makes perfect use of the smaller image, and
therefore the lens appears bigger. Nothing to worry about!

Another use of percentage of cropping applies to people cropping out a
small
piece of the image but not re-sizing it. So if you take a 640 x 800 pixel
piece
of a 3000 x 2000 pixel image and Email it to someone, you have sent them a
100%
crop of the image. They really mean 100% size... of the piece. If you
cropped it
and resized it smaller, you might say it's a 50% crop if you re-sized it
50%,
but the actual crop percentage size is unknown! (Unless you do the math
and
back-track...) The word crop here means 'piece'.

As for a percentage crop by itself, you would usually go by dimension, so
a 50%
crop of a 1000 x 1000 size image would be 500 x 500. Note that the area
here is
actually 25%, so it is possible for someone to say that it IS a 25% crop
by
area. Also in this case there would be no such thing as 100% crop... it's
like
dividing by zero.... "I made this 200x200 a 200x200, 100% crop"... I did
nothing!

Ain't language fun?


And so is mathematics. Dividing by Zero gives Infinity. Dividing by One
gives the no change answer.

You knew that of course, and it was just a typo.

Roy G

On Tue, 12 May 2009 11:38:17 +0100, "Roy G" wrote:


wrote in message
.. .
On Mon, 11 May 2009 14:08:09 -0700 (PDT), dohc46
wrote:

After reading review after review after review 1 main question keeps
arising in my head.....what are they talking about:
"cropped my photo xxx%"
When I think of cropping, here is the extent of my knowledge.......

I look at my daughter somewhere towards the middle of the photo and
too far for my liking (she looks to small) and then the next think i
notice is, "darn it Aunt Ethel how did you get in the photo to the
left", & "darn it Fido why are you in the picture to the right peeing"
& "I wish I could bring my daughter closer"........AHHHHH I know the
answer....

I then proceed to grab the lasso or square line or whatever says crop
on my software, I put it around my daughter and then hit
apply......BOOM magic: she is closer/bigger, dog is gone & auntie is
gone.....that is my extent of cropping.

What are people talking about when they say, "my picture is cropped
100%", "my picture is cropped xxx%"....when I do my cropping there is
no % number popping up anywhere.....so how do they know what % is
being cropped..........

Probably a bad guess, I'll admit......but could it be that the
original photo was (example) 5 megabytes then after cropping it is now
only 2.5 megabytes.....would that be considered 100% cropping?

There are a few meanings to crop factor or percentage.

One is the crop factor required to match a digital cameras' small sensor
to the
size of 35mm film. In this case, the crop factor is merely the percentage
needed
by a particular camera, and YOU don't have to crop anything or worry about
it
The usual crop factor is 1.5, which means that if you use a 50mm lens it
becomes
equal to a 75mm lens on the other camera, (50 x 1.5 = 75). Note that the
digital
sized lens would create a cropped image if used on the larger camera
because it
can't throw as large an image on the film as it does on the small sensor.
The
small sensor camera however makes perfect use of the smaller image, and
therefore the lens appears bigger. Nothing to worry about!

Another use of percentage of cropping applies to people cropping out a
small
piece of the image but not re-sizing it. So if you take a 640 x 800 pixel
piece
of a 3000 x 2000 pixel image and Email it to someone, you have sent them a
100%
crop of the image. They really mean 100% size... of the piece. If you
cropped it
and resized it smaller, you might say it's a 50% crop if you re-sized it
50%,
but the actual crop percentage size is unknown! (Unless you do the math
and
back-track...) The word crop here means 'piece'.

As for a percentage crop by itself, you would usually go by dimension, so
a 50%
crop of a 1000 x 1000 size image would be 500 x 500. Note that the area
here is
actually 25%, so it is possible for someone to say that it IS a 25% crop
by
area. Also in this case there would be no such thing as 100% crop... it's
like
dividing by zero.... "I made this 200x200 a 200x200, 100% crop"... I did
nothing!

Ain't language fun?


And so is mathematics. Dividing by Zero gives Infinity. Dividing by One
gives the no change answer.

You knew that of course, and it was just a typo.

Roy G


You're absolutely right. I think I meant to say that you've done zero... looks
like I posted a zero!