Home · Register · Join Upload & Sell

Moderated by: Fred Miranda

New fredmiranda.com Mobile Site

New Feature: SMS Notification alert

New Feature: Buy & Sell Watchlist

FM Forums | Canon Forum | Join Upload & Sell

2 end

Archive 2011 · A stupid question

shoenberg3
Offline
• • •
Upload & Sell: Off

p.1 #1 · p.1 #1 · A stupid question

If 10 mb 1.6x crop camera and a 16mb FF camera took a picture of the same scene with the same lens, if the FF image is cropped, the results should be exactly identical, right?

Maybe since sensor is smaller on the crop camera the light is gathered differently? Maybe smaller sensors behave differently for some reason?

I am probably just crazy.

Mar 08, 2011 at 04:37 AM

ciprian.trofin
Offline
• •
Upload & Sell: Off

p.1 #2 · p.1 #2 · A stupid question

The FF camera must be 25.6MB

Mar 08, 2011 at 04:46 AM

melcat
Offline
• • • •
Upload & Sell: Off

p.1 #3 · p.1 #3 · A stupid question

What is this "mb" of which you speak?

m = milli
M = mega
Mpx or sometimes Mp = megapixel
B = byte = 8 bits since about the 1960s.
b = bit

The OP can gain some insight by looking at (pictures of) a full frame and 1.6 crop camera with the body cap off. Understanding will follow.

Mar 08, 2011 at 04:51 AM

Ian.Dobinson
Offline
• • • • • •
Upload & Sell: Off

p.1 #4 · p.1 #4 · A stupid question

shoenberg3 wrote:
If 10 mb 1.6x crop camera and a 16mb FF camera took a picture of the same scene with the same lens, if the FF image is cropped, the results should be exactly identical, right?

Maybe since sensor is smaller on the crop camera the light is gathered differently? Maybe smaller sensors behave differently for some reason?

I am probably just crazy.

Nope.
Pixel denisity's are different
in your example you could say the 10mp 1.6 crop is a 40D and the 16mp is a 1Ds2 (thats the closest)
from the chart on The Digital Picture
40D is 5.7
!Ds2 is 7.2
The old 6mp croppers have a very close pixel density to the 1Ds2

If your looking for the closest FF to 1.6 crop equive that canon have at the moment its the 21mp 5D2 and the old 8mp 20/30D

the chart is in this link
http://www.the-digital-picture.com/Reviews/Canon-EOS-1Ds-Mark-III-Digital-Camera-Review.aspx

Mar 08, 2011 at 05:14 AM

shoenberg3
Offline
• • •
Upload & Sell: Off

p.1 #5 · p.1 #5 · A stupid question

Ah that was a trivial mistake. I should reword it to say that they have same pixel density.

Mar 08, 2011 at 05:16 AM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #6 · p.1 #6 · A stupid question

Yes, the same, assuming same pixel density, which would require the square of the crop factor.

The important consideration is that you have the same distance, hence the same perspective. You can either change the focal length to get the same angle of view or you can crop. With a different lens you will get a different depth of field at the same aperture. With the same lens cropped, you are enlarging the blur disks (Circles of Confusion) the same amount and will get an identical photo.

Mar 08, 2011 at 06:33 AM

dcains
Offline
• • • • •
Upload & Sell: Off

p.1 #7 · p.1 #7 · A stupid question

Pixel density differences won't make any real visible difference in a print.

Nobody mentioned the DOF difference? Please do a search. It's been discussed here ad nauseum, including a few threads in the last few weeks.

Mar 08, 2011 at 06:51 AM

melcat
Offline
• • • •
Upload & Sell: Off

p.1 #8 · p.1 #8 · A stupid question

dcains wrote:
Nobody mentioned the DOF difference?

I guess because it was fairly clear from the OP's wording that both pictures were taken with the camera in the same position - so there is no depth of field difference.

Mar 08, 2011 at 07:02 AM

NDP_2010
Offline
• • •
Upload & Sell: Off

p.1 #9 · p.1 #9 · A stupid question

I think the light gathering should be equal (if you do not account for light dropping off at the edges of the glass) If you have a certain intensity hitting 1cm square, you have double the intensity hitting 2cm square, so overall the same intensity / area.

Mar 08, 2011 at 07:04 AM

wickerprints
Offline
• • • •
Upload & Sell: Off

p.1 #10 · p.1 #10 · A stupid question

The simplest way to think of such a comparison is to consider the effect of cropping a full frame sensor at the APS-C boundary. The result is an image equivalent to one taken with an APS-C sensor whose pixel count is equal to the number of pixels in the crop.

For example: the 5D2 has a resolution of 5616 x 3744 px. The central APS-C portion of the sensor would be comprised of the central 3510 x 2340 px region. Thus, if you cropped the full image down to the center 3510 x 2340 px, then you would have the equivalent of an image that had been taken with an 8.2 megapixel APS-C sensor, with the same lens, at the same subject distance, and the same exposure.

In practice, there are no such pairs of APS-C and full frame sensors--even if the pixel density were exactly equal, the sensor technology is not, due to the fact that such sensors are not made contemporaneously. Newer innovations in CMOS sensor fabrication have improved noise and dynamic range at equivalent ISOs.

Mar 08, 2011 at 07:34 AM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #11 · p.1 #11 · A stupid question

dcains wrote:
Nobody mentioned the DOF difference?

melcat wrote:
I guess because it was fairly clear from the OP's wording that both pictures were taken with the camera in the same position - so there is no depth of field difference.

Not only that, but it was specified the same focal length. Same position (distance), same crop, same focal length, same enlargement, same viewing distance, same viewer visual acuity: therefore same depth of field.

Mar 08, 2011 at 03:03 PM

dcains
Offline
• • • • •
Upload & Sell: Off

p.1 #12 · p.1 #12 · A stupid question

Monito wrote:
Not only that, but it was specified the same focal length. Same position (distance), same crop, same focal length, same enlargement, same viewing distance, same viewer visual acuity: therefore same depth of field.

Wrong. Do the math. Sensor size makes a difference. If as you state: same position (distance), same focal length - the DOF will be smaller with the FF body. Try it and see for yourself, or use this calculator:

http://www.dofmaster.com/dofjs.html

I'm not sure what you mean by same viewing distance or same viewer visual acuity, but they don't factor into the DOF calculations.

Mar 08, 2011 at 03:24 PM

garyvot
Offline
• • • •
Upload & Sell: On

p.1 #13 · p.1 #13 · A stupid question

wickerprints wrote:
The simplest way to think of such a comparison is to consider the effect of cropping a full frame sensor at the APS-C boundary. The result is an image equivalent to one taken with an APS-C sensor whose pixel count is equal to the number of pixels in the crop.

For example: the 5D2 has a resolution of 5616 x 3744 px. The central APS-C portion of the sensor would be comprised of the central 3510 x 2340 px region. Thus, if you cropped the full image down to the center 3510 x 2340 px, then you would have the equivalent...Show more →

+1

Mar 08, 2011 at 03:28 PM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #14 · p.1 #14 · A stupid question

dcains wrote:
Wrong. Do the math. Sensor size makes a difference. If as you state: same position (distance), same focal length - the DOF will be smaller with the FF body.

I did the math. I often post the point you make for full frame versus crop factor, but in this case, the OP specified that the full-frame sensor is to be cropped the same a the 1.6x crop factor sensor. Hence, I wrote "same crop", which you neglected or omitted.

Mar 08, 2011 at 03:28 PM

dcains
Offline
• • • • •
Upload & Sell: Off

p.1 #15 · p.1 #15 · A stupid question

Do you really think cropping a photo changes its DOF? Sorry, but you're just not thinking about this correctly. Do you see any DOF difference between the original and crop version of these two images:

http://deanwcains.smugmug.com/photos/1210168147_g7RiJ-L.jpg

http://deanwcains.smugmug.com/photos/1210168296_MfXh7-L.jpg

A few screen grabs of the DOF calculations, 7D (1.6x) versus 1Ds2 (FF):

http://deanwcains.smugmug.com/photos/1210161456_j8fGW-L.jpg

http://deanwcains.smugmug.com/photos/1210161510_3Sukp-L.jpg

Mar 08, 2011 at 03:38 PM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #16 · p.1 #16 · A stupid question

dcains wrote:
I'm not sure what you mean by same viewing distance or same viewer visual acuity, but they don't factor into the DOF calculations.

Do the math. They most certainly do factor in. If you make an 8 x 12 inch print and look at it from about 20 inches away, it will appear to have a particular depth of field. However, if you print the same image at 48 x 72 inches size and look at it from 16 to 20 inches away, you will see things blurry that you perceived as sharp in the 8 x 12 inch print from the same viewing distance; that is to say: less depth of field. You have to look at the large print at a distance of 120 inches to perceive the same depth of field.

Similarly, if someone has poor visual acuity due to loss of retinal cells due to disease, then they will perceive a greater degree of blur and because they are used to this, they will have a greater tolerance of blur and thus will perceive a greater depth of field than someone with high visual acuity.

Do the math with a real Depth of Field calculator that accounts for all the factors: http://eosdoc.com/jlcalc/ [edited to include link]

Do the study to understand all the factors, starting with an overview http://en.wikipedia.org/wiki/Depth_of_field and proceeding to more primary references as needed or desired.

Edited on Mar 08, 2011 at 03:42 PM · View previous versions

Mar 08, 2011 at 03:38 PM

dcains
Offline
• • • • •
Upload & Sell: Off

p.1 #17 · p.1 #17 · A stupid question

You can't be serious. Print size changes DOF? Retinal disease changes DOF? I'm done.

Mar 08, 2011 at 03:41 PM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #18 · p.1 #18 · A stupid question

dcains wrote:
You can't be serious. Print size changes DOF? Retinal disease changes DOF? I'm done.

Yup. You were done a long time ago when you stopped thinking about it and stopped listening to reason. Besides you contradict yourself.

Mar 08, 2011 at 03:43 PM

Monito
Offline
• • • • • •
Upload & Sell: Off

p.1 #19 · p.1 #19 · A stupid question

dcains wrote:
Do the math. Sensor size makes a difference.

You contradict yourself when you later write:

dcains wrote:
Do you really think cropping a photo changes its DOF? Sorry, but you're just not thinking about this correctly.

Cropping is exactly equivalent to changing sensor size. That's why crop-factor cameras (the ones with the sensors smaller than full-frame 24 x 36 mm sensors) are called "crop-factor".

Mar 08, 2011 at 03:47 PM

JSXX
Offline
•
Upload & Sell: Off

p.1 #20 · p.1 #20 · A stupid question

dcains wrote:
Wrong. Do the math. Sensor size makes a difference. If as you state: same position (distance), same focal length - the DOF will be smaller with the FF body. Try it and see for yourself, or use this calculator:

http://www.dofmaster.com/dofjs.html

dcains wrote:
A few screen grabs of the DOF calculations, 7D (1.6x) versus 1Ds2 (FF):

http://deanwcains.smugmug.com/photos/1210161456_j8fGW-L.jpg

http://deanwcains.smugmug.com/photos/1210161510_3Sukp-L.jpg

I have always heard a FF sensor has a smaller dof than a crop sensor, but the calculator shows 1.84 ft tor the 7D and 2.94 ft for the 1Ds?

Mar 08, 2011 at 04:04 PM

1 2 end
FM Forums \| Canon Forum \| Join Upload & Sell 1 2 end

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.