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Old Aug 29, 2010, 5:16 PM   #41
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Justin,

I'm curious how you change the laws of mathematics to prove your hypothesis. Perhaps you can have a mathematician explain to us how you were able to do that.
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Old Aug 29, 2010, 5:20 PM   #42
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@ Mark, you can have my 400 2.8 and 200 2.o when you pry them from my cold.........LOL
Spot the new 'boy'..... didn't Jim tell you I'm 6'6" and 260lb?? LOL
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Old Aug 29, 2010, 5:23 PM   #43
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For example, the math tells us (simplified by using the depth of field calculator) that at 100 feet. 100mm lens at f4:
full frame (c=0.03) has DOF of 0.71 feet
aps-H (c=0.023) has DOF of 0.54 feet
aps-C (1.6 version at c=0.019) has DOF of 0.45'

Now those are close but not the same. What might surprise people is the depth-of-field for the smaller sensor is actually smaller. That's right - smaller. But I look forward to the mathematical explanation for how Justin has turned the mathematics of depth-of-field on their head so that circle of confusion no longer plays a part.
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Old Aug 29, 2010, 5:38 PM   #44
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Spot the new 'boy'..... didn't Jim tell you I'm 6'6" and 260lb?? LOL
Good that means I can take you out at the knees and youll drop hard and fast!

John, Im not trying to be difficult. I have heard it all and from many different sides of the fence. I have run the math too many times but in the end when 3 bodies were compared with the same 300 mounted on a tripod and were focused at the same target with a yardstick beside them the infocus marks on the stick were the same give or take 1/32 of an inch at 10 ft which may have been contributed by the calibration of the body or the "circle of confusion". Can mathematics narrow it down to .00000000000000000000001mm well yes but unless your taking photos of microbes on a gnats behind its not very practical. My point is that this doesnt have to go to the molecular level and its not rocket science. The misconception that is largely presented is as Mark stated that when you fill the frame with a FF using the same lens to match that of a 1.6 crop the DOF will change but not as a result of sensor size but changing the focal plane by closing it to get the subject the same size on both bodies.
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Old Aug 29, 2010, 5:44 PM   #45
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This will give someone an interesting read if they like http://en.wikipedia.org/wiki/Circle_of_confusion

From what I remember isn't it to do with the printing of the final image at a set size (8x10 can't remember???) and then observing it...... I could be wrong and am about to sleep so haven't even read the link I posted. If that is the case, when cropping you would find the results to be the same as when you print them the are all the same size. But when you print them with their original field of view then you get the differences.

I'm looking forward to hearing the replies when I get up.
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Old Aug 29, 2010, 5:45 PM   #46
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Originally Posted by JohnG View Post
For example, the math tells us (simplified by using the depth of field calculator) that at 100 feet. 100mm lens at f4:
full frame (c=0.03) has DOF of 0.71 feet
aps-H (c=0.023) has DOF of 0.54 feet
aps-C (1.6 version at c=0.019) has DOF of 0.45'

Now those are close but not the same. What might surprise people is the depth-of-field for the smaller sensor is actually smaller. That's right - smaller. But I look forward to the mathematical explanation for how Justin has turned the mathematics of depth-of-field on their head so that circle of confusion no longer plays a part.
Now that just threw the entire myth 180 degrees that a FF sensor has a more shallow DOF.
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Old Aug 29, 2010, 5:47 PM   #47
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For example, the math tells us (simplified by using the depth of field calculator) that at 100 feet. 100mm lens at f4:
full frame (c=0.03) has DOF of 0.71 feet
aps-H (c=0.023) has DOF of 0.54 feet
aps-C (1.6 version at c=0.019) has DOF of 0.45'

Now those are close but not the same. What might surprise people is the depth-of-field for the smaller sensor is actually smaller. That's right - smaller. But I look forward to the mathematical explanation for how Justin has turned the mathematics of depth-of-field on their head so that circle of confusion no longer plays a part.
Its not difficult. Its called enlargement.

.3/1.3 = .23
.3/1.6 = .1875

If you blow up the crop to the same size, COC is the exact same.

This argument is getting silly.
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Old Aug 29, 2010, 5:48 PM   #48
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Originally Posted by Mark1616 View Post
This will give someone an interesting read if they like http://en.wikipedia.org/wiki/Circle_of_confusion

From what I remember isn't it to do with the printing of the final image at a set size (8x10 can't remember???) and then observing it...... I could be wrong and am about to sleep so haven't even read the link I posted. If that is the case, when cropping you would find the results to be the same as when you print them the are all the same size. But when you print them with their original field of view then you get the differences.

I'm looking forward to hearing the replies when I get up.

Now my brain hurts!

We can go all technical, my point was simply that in a practical situation The difference is moot.
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Old Aug 29, 2010, 5:49 PM   #49
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Its not difficult. Its called enlargement.

.3/1.3 = .23
.3/1.6 = .1875

If you blow up the crop to the same size, COC is the exact same.

This argument is getting silly.

Touche
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Old Aug 29, 2010, 6:05 PM   #50
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Touche
AND DOF is a property of physical aperture (not f-number), focal length, and distance to subject.

QED
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