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06-03-2013, 04:12 PM   #16
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QuoteOriginally posted by JinDesu Quote
He is accounting for (and asking for) DOF difference between a 200 F2.8 on APSC vs the 300 F2.8 on FF. Boriscleto has given the difference as 3" if you have focused on a subject 30 feet away. OP has asked a very specific question.
Talk is cheap

06-03-2013, 07:41 PM   #17
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QuoteOriginally posted by konraDarnok Quote
A Canon 6D with a 300mm 2.8 lens is 8500 dollars new. A Pentax K5II with a 200mm 2.8 lens is 2200. That's quite a price spread for a change in the depth of field, but does anyone have any samples of the same subject matter to illustrate what you're buying for 6300 dollars?
You'd get about 1.3 stops more DOF control (ie 300 f/2.8 on FF =~ 200 f/1.8 on aps-c,) but that is a hefty price to pay for that. No idea about the relative IQ of each lens beyond the FOV/DOF difference the format brings, the 300 2.8 may be excellent. (It should keep a very high resale value, for one thing )
06-03-2013, 07:45 PM   #18
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QuoteOriginally posted by konraDarnok Quote
Losing a full stop is going change your exposure or ISO. Less of an apples to apples comparison IMHO.
Actually it's more of an apples-apples comparison. In FOV/DOF, 200 f/2.8 on aps-c almost exactly equals 300 f/4 on FF.

If you want to maintain shutter speed with the FF f/4 lens, you can bump up ISO that stop to do so, and your images should have about the same amount of visible noise, assuming similar sensor generations.

In other words - here's that dreaded phrase! ... 200 2.8 aps-c and 300 f4 FF will create equivalent images.

.
06-03-2013, 07:49 PM   #19
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Here is a 7d and 200mm f2.8 shot



and 1dsii 300mm f2.8



closest I had and it was cloudy that morning. Not a lot of difference unless you are close it seems to me. Its nice to have different crop bodies to swap focal lengths. A 300mm f4 is a nice bargain, I got a real nice used one for $700 ef mount. It is a whole lot like my old DA*300, but with fast focus.

06-04-2013, 10:18 AM   #20
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QuoteOriginally posted by borno Quote
Here is a 7d and 200mm f2.8 shot



and 1dsii 300mm f2.8



closest I had and it was cloudy that morning. Not a lot of difference unless you are close it seems to me. Its nice to have different crop bodies to swap focal lengths. A 300mm f4 is a nice bargain, I got a real nice used one for $700 ef mount. It is a whole lot like my old DA*300, but with fast focus.




Well if you wouldn't mind answering my question as you have the requisite lenses and formats. . . A picture of lawn chair at 100' or so with both setups would do it (or whatever you think would be most illustrative). Just a straight forward test of the exact same subject matter.
06-04-2013, 10:55 AM   #21
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borno? you do understand that an F -stop is a measure of light transmission and doesn't directly relate to DoF don't you? If people want to talk about DoF equivalence, that's a different (albeit related) topic.

F-number - Wikipedia, the free encyclopedia
06-04-2013, 12:50 PM   #22
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QuoteOriginally posted by normhead Quote
borno? you do understand that an F -stop is a measure of light transmission and doesn't directly relate to DoF don't you? If people want to talk about DoF equivalence, that's a different (albeit related) topic.

F-number - Wikipedia, the free encyclopedia
Really, so would shutter speed or ISO instead change the DOF ? Try shooting a 300mm at F2.8 then at F22 then see if DOF changes.
06-04-2013, 12:55 PM   #23
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QuoteOriginally posted by jsherman999 Quote
Actually it's more of an apples-apples comparison. In FOV/DOF, 200 f/2.8 on aps-c almost exactly equals 300 f/4 on FF.

In other words - here's that dreaded phrase! ... 200 2.8 aps-c and 300 f4 FF will create equivalent images.
Well the combo D600 + 300mm/f4 is 73 % more expensive then the combo K-5 II + 200mm/f2.8.

(but that is only 1200 euro and a once spending money)


Last edited by RonHendriks1966; 06-04-2013 at 01:03 PM.
06-04-2013, 01:49 PM   #24
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QuoteOriginally posted by konraDarnok Quote
Well if you wouldn't mind answering my question as you have the requisite lenses and formats. . . A picture of lawn chair at 100' or so with both setups would do it (or whatever you think would be most illustrative). Just a straight forward test of the exact same subject matter.
I'll try to get something by the weekend (if I don't forget)
06-04-2013, 02:20 PM   #25
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QuoteOriginally posted by jogiba Quote
Really, so would shutter speed or ISO instead change the DOF ? Try shooting a 300mm at F2.8 then at F22 then see if DOF changes.
Just read the article on the Wicki, I can't be bothered with this nonsense.
06-04-2013, 03:51 PM   #26
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Actually, if I am not mistaken, you can modify dof with an improper exposure (over exposing for example). Now, I can be wrong and hopefully someone will correct me if I am...
06-04-2013, 03:57 PM   #27
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QuoteOriginally posted by joe.penn Quote
Actually, if I am not mistaken, you can modify dof with an improper exposure (over exposing for example). Now, I can be wrong and hopefully someone will correct me if I am...
Well, if you overexpose, then you can lose details in the highlights...but I'd say that DoF, for a given focal length and focusing distance, is simply a property having to do with the aperture opening only, and /not/ the exposure (over and under).

In other words (for a given focal length and focusing distance): keeping the aperture constant, I believe that the same DoF will be obtained regardless of if the image be over or underexposed.
06-04-2013, 04:12 PM   #28
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QuoteOriginally posted by normhead Quote
Just read the article on the Wicki, I can't be bothered with this nonsense.
Depth of field increases with f-number, as illustrated in the image here. This means that photographs taken with a low f-number will tend to have subjects at one distance in focus, with the rest of the image (nearer and farther elements) out of focus.
F-number - Wikipedia, the free encyclopedia
06-04-2013, 04:36 PM - 1 Like   #29
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QuoteOriginally posted by jogiba Quote
Depth of field increases with f-number, as illustrated in the image here. This means that photographs taken with a low f-number will tend to have subjects at one distance in focus, with the rest of the image (nearer and farther elements) out of focus.
F-number - Wikipedia, the free encyclopedia
Exactly... so while DoF changes with F-number... and the DoF will be different across systems, the F-number with the same shutter and ISO will remain the same across all systems. F 2.8 on one system when looking at exposure, because the F-stop is one of the units by which exposure is measured. DoF on the other hand is the distance between the closest and furthest points in acceptable focus. It is not a measure of available light as is an f-stop, but is a distance measured in inches or mm. The cost of confusing these two measures is endless confusion, incorrect assumptions and misleading arguemnts that while factually correct in a limited perspective, create semantic juxtapositions that create factual confusion.

How's your head?

If we use the F-stop as a measure of the intensity of the light transmitted through the lens and the DoF as a distance between two points, the confusion will be eliminated. The fact that DoF changes with aperture doesn't make DoF the same as aperture. As soon as you wrap your head around that, you can see a lot of the gobbly gook around "equivalency" for what it is. Confusion caused by trying to condence two different concepts into one term.
06-04-2013, 09:23 PM   #30
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QuoteOriginally posted by normhead Quote
gobbly gook around "equivalency" for what it is


Equivalency:




Looks pretty clear to me.
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