Just GIVE IT UP!
Sheesh this is a 'I am right you a wrong' forum.
You guys use the same gear obviously have the same interests but quite obviously just hate each other.
Back to the lounge for me!
Cheers,
Jasin.
You don't hear anything different then what I have been saying all along. I am going to print larger with a 1Ds Mark II then I would if I was using a 1D Mark II It is that simple. If I crop my 1Ds Mark II image by a factor of 1.3 I have the EXACT same image, give or take a few pixels.
nsbca wrote:
Let's go through a real life scenario. I have a FF 1Ds. I shoot a picture crop and enlarge the image to say 54x24. Nothing hard about that is there? Can I do that with my 300D? Not very well. If I wanted the same aspect ratio I would print the image from the 300D at 34x15. That would give me a very close DOF (+/-) and the print would be close to the same in clarity and sharpness.
1) Yes, I think you have just said that the DoF remains the same if the magnification ratio is the same. On paper, with the 8x10 standard in place (all other variables staying the same) the DOF will change if the sensor size changes.
2) Yes. And that's why you can't use the DoF scales unmodified - the answer to the original question on page1 In the practical world it remains a constant.
3) Yes, if you print your 1dDs images bigger than your 300D, 350D, 10D etc images by the 1.6 factor. (see 1) above)
It becomes a variable if you don't use the 1.6 factor. (see 2) above )
nsbca wrote:
When my 1Ds Mark II comes in next week I will be glad to do this.
There's no need for you to do the test any more now that you said the following (bold text my emphasis): nsbca wrote:
The above calculations are 100% correct if all thing given - focal length, aperture diameter, distance from subject and (your 8x10) size of print and viewing distance from print remain the same. If the sensor size changes under these conditions the image will indeed change and the percieved DOF will also change. I have no problem with that whatsoever.
That convinces we that we actually are in agreement with respect to fundamentals.
I think we still differ on other details (e.g. the validity of the DOF scales for different print sizes), but that's a minor quibble.
Jeff Donald wrote:
DOF didn't really exist until there was photography (capturing a 3 dimensional world on a 2 dimensional medium). Try to find a 16th Century painting that displays DOF. DOF is an optical phenomenon that can be described mathematically, but it is hardly a "law of physics" as some have claimed.
Perhaps not under this definition that we have today, but this "optical phenomenon" as you put it, has been around for as long as creatures on this planet have had eyesight. Perhaps instead of "depth-of-field", you would prefer to call it "depth-of-focus" or "depth perception".
Hold your finger four inches in front of your face and see if you can focus on it and something 100 feet away at the same time. If you can't, it is because the depth-of-field is too great for your eyes optics to handle. People with poor depth perception are looking at a shallower depth-of-field than those with good depth perception.
Hold your finger four inches in front of your face and see if you can focus on it and something 100 feet away at the same time. If you can't, it is because the depth-of-field is too great for your eyes optics to handle.
I think you're talking minimum focus distance not DOF. My 50 mm at f/16 can't focus on something 4 inches in front of it and have an object 100 feet away in focus. However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time. Prior to Lippershey and Galileo DOF was not known. It requires optical lenses to perform the phenomenon. I think you're confusing depth perception, which requires stereo viewing, with DOF.
Jeff Donald wrote:
However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time.
I don't disagree with anything you've said about DoF to this point, but can you clarify this statement?
Perhaps it's just my eyeglasses that are distorting the world in ways that my eyes wouldn't if they weren't astigmatic, but if I close one eye and focus on my finger at arm's length, then switch focus to an object about 3 times as far away (box of Ilford Galerie paper), I can see the text come into focus. Conversely, if I focus on the text, then on my finger (again with one eye closed) my finger appears to become sharper and there's no way I can read the text.
Thus, it would appear that just one eye is unable to focus both on the text and my finger.
If I use both eyes, the stereo vision issue comes into play, and objects at a closer distance clearly go double. However, holding up something with text and looking at it (while leaving my eyes focused on the box of paper), the text not only is doubled, but a single copy looks blurry.
"DoF is controlled by four factors;the actual "f-stop" at which the picture is taken, the focal length of the length being used,the size of the subject being photograped, and the distance between camera and the subject"
------------------ John Shaw
If all the parameters except focal length are same, then a 50mm lens on a camera which has 1.6 crop factor produces exact same FoV as a 80mm lens on a FF body.So here only difference is the focal length of the lens being used.
Now as per the above definition , longer the focal length, narrower the DoF.
I'm going to start a pool on when this thread will finally die. However, while it's still alive...
What in the world does the size of the subject being photographed have to do with the depth of field? And as much as I admire Mr. Shaw, he seems to be making the same oversight that has contributed to much of the controversy in this thread: the relationship between circle of confusion, film size, and print size.
Anyway, setting that aside, yes, Manoj, that's why crop cameras have a larger depth of field when the field of view is otherwise identical.
"DoF is controlled by four factors;the actual "f-stop" at which the picture is taken, the focal length of the length being used,the size of the subject being photograped, and the distance between camera and the subject"
------------------ John Shaw
The size of the subject? Where did that come from
rcmanoj wrote:
If all the parameters except focal length are same, then a 50mm lens on a camera which has 1.6 crop factor produces exact same FoV as a 80mm lens on a FF body.So here only difference is the focal length of the lens being used.
Actaully if you are going on that track it would be closer to a 63mm lens and there would be more different about the resultng image then just saying what focal length you used. The light from a 50mm and a 63mm lens travel at different angles and thus would affect the aestetics of the image. And then again that furmula only works if both images are printed and viewed the same size and from the same distance.
jdaily wrote:
63mm? 50 * 1.6 = 80. Where did 63 come from?
That's not how the DOF formula works.
A FF sensor is not 1.6 times larger then a 1.6 crop sensor in area. The full frame is more then twice as large, so applying the 1.6 directly to the lens will not get you the correct FOV.
I have 3 of his books, and only in "Landscape Photography" does he make that statement. I think he was trying to say image size, because image size pops up again (rather obscurely) about 5 paragraphs later. Or...
In "Closeups in Nature", he says this:
If the image size and the aperture remain the same, all focal-length lenses give the same depth of field...If you photograph a subject at life-size with a 50mm lens and then move back and photograph it again at life-size with a 200mm lens at the same f-stop, the depth of field will be the same.
Perhaps that's where he was headed with "size of the subject" in "Landscape Photography".
