The longer the lens, the less the depth of field. The bigger the sensor/ film area, the less the depth of field.
There is a lot of misinformation on this subject on the net (the DoF article on LL, for example).
The old magnification/ aperture line isn't strictly true, nor of much use in the real world..
I knew this would happen... Its not entirely true, its a myth.
Anyway, I figured I might try to do a quick, painless end-around on the subject, and try to tell you what actually matters about DoF. I'm going to ignore the technical explanation: because That Way Lie Dragons; Abandon Hope All Ye Who Enter there; etc. I'm doing that on purpose, so please don't write to fill me in.1. By far—by far—the most important factor in how much DoF you'll get is your distance setting. The farther the distance between the lens and whatever it's focused on, the more you'll get in the DoF.2. Next most important: the focal length of the lens relative to the size of the film/sensor. Again, on principle, let's forget all the tech-talk about what's "really" going on and the scientific explanations and all that. All you need to remember is that the longer the lens, the less apparent DoF there will be in your shots. And, big jumps matter, little ones not so much; there's not that much difference between an 85mm and a 100mm, or between a 24mm and a 20mm. Very roughly speaking, when there's a 2x or 1/2x difference in focal length, you're going to have noticeably different DoF characteristics to learn.3. Last: aperture setting. When I was teaching, all my kids had to memorize the following phrase: "The higher the number the smaller the hole the greater the depth of field." Can you see differences? Of course. But again, it takes relatively bigger jumps to really matter all that much. The other two factors matter more.
But if you backed up the 300mm lens so that the overall broad framing of the shot was the same (i.e. same overall magnification, not just of the front test chart) then the DOF would be the same.
D3s? Or D3ses? I'd need 20Mp minimum to justify such a big camera. If you're working with a single camera/ format, the following is all you need to know:QuoteAnyway, I figured I might try to do a quick, painless end-around on the subject, and try to tell you what actually matters about DoF. I'm going to ignore the technical explanation: because That Way Lie Dragons; Abandon Hope All Ye Who Enter there; etc. I'm doing that on purpose, so please don't write to fill me in.1. By far—by far—the most important factor in how much DoF you'll get is your distance setting. The farther the distance between the lens and whatever it's focused on, the more you'll get in the DoF.2. Next most important: the focal length of the lens relative to the size of the film/sensor. Again, on principle, let's forget all the tech-talk about what's "really" going on and the scientific explanations and all that. All you need to remember is that the longer the lens, the less apparent DoF there will be in your shots. And, big jumps matter, little ones not so much; there's not that much difference between an 85mm and a 100mm, or between a 24mm and a 20mm. Very roughly speaking, when there's a 2x or 1/2x difference in focal length, you're going to have noticeably different DoF characteristics to learn.3. Last: aperture setting. When I was teaching, all my kids had to memorize the following phrase: "The higher the number the smaller the hole the greater the depth of field." Can you see differences? Of course. But again, it takes relatively bigger jumps to really matter all that much. The other two factors matter more.If you're using multiple formats, (which Paul isn't, though he is comparing his kit to...) all you need add is that:4. for the same angle of view and aperture, the bigger format will have less depth of field.(though this will entail a longer lens, so you could just stick with rule 2...)When I want selective focus effects, ie isolating a subject from the background, I prefer to use a larger format than a longer lens. Mainly because I'm loathe to lose the background, and hence the context, but its also subtler. For a good illustration, compare Alex Messenger's and Al Lee's stuff, as they each tend to use the opposite method. QuoteBut if you backed up the 300mm lens so that the overall broad framing of the shot was the same (i.e. same overall magnification, not just of the front test chart) then the DOF would be the same.No it wouldn't - that's the whole point of the article. Not just the depth of field would change, but also how it falls either side of the point of focus would change (the 25mm would obey the 1/3-2/3 rule, the 300mm 1/2 and 1/2). None of this has huge relevance to actual photogaphy though. Its a shame the myth is so widely circulated as it means at some point you have to relearn everything, not to progress your photography, but just to ensure you aren't wrong.
5. THERE IS ONLY ONE CRITICAL PLANE OF FOCUS, EVERYTHING ELSE IN DEPTH OF FIELD IS A COMPROMISE RELEGATED TO "USABLE" FOCUS.
D3X then?
Quote from: Johnny Brown on February 19, 2010, 11:08:45 amD3s? Or D3ses? I'd need 20Mp minimum to justify such a big camera. If you're working with a single camera/ format, the following is all you need to know:QuoteAnyway, I figured I might try to do a quick, painless end-around on the subject, and try to tell you what actually matters about DoF. I'm going to ignore the technical explanation: because That Way Lie Dragons; Abandon Hope All Ye Who Enter there; etc. I'm doing that on purpose, so please don't write to fill me in.1. By far—by far—the most important factor in how much DoF you'll get is your distance setting. The farther the distance between the lens and whatever it's focused on, the more you'll get in the DoF.2. Next most important: the focal length of the lens relative to the size of the film/sensor. Again, on principle, let's forget all the tech-talk about what's "really" going on and the scientific explanations and all that. All you need to remember is that the longer the lens, the less apparent DoF there will be in your shots. And, big jumps matter, little ones not so much; there's not that much difference between an 85mm and a 100mm, or between a 24mm and a 20mm. Very roughly speaking, when there's a 2x or 1/2x difference in focal length, you're going to have noticeably different DoF characteristics to learn.3. Last: aperture setting. When I was teaching, all my kids had to memorize the following phrase: "The higher the number the smaller the hole the greater the depth of field." Can you see differences? Of course. But again, it takes relatively bigger jumps to really matter all that much. The other two factors matter more.If you're using multiple formats, (which Paul isn't, though he is comparing his kit to...) all you need add is that:4. for the same angle of view and aperture, the bigger format will have less depth of field.(though this will entail a longer lens, so you could just stick with rule 2...)When I want selective focus effects, ie isolating a subject from the background, I prefer to use a larger format than a longer lens. Mainly because I'm loathe to lose the background, and hence the context, but its also subtler. For a good illustration, compare Alex Messenger's and Al Lee's stuff, as they each tend to use the opposite method. QuoteBut if you backed up the 300mm lens so that the overall broad framing of the shot was the same (i.e. same overall magnification, not just of the front test chart) then the DOF would be the same.No it wouldn't - that's the whole point of the article. Not just the depth of field would change, but also how it falls either side of the point of focus would change (the 25mm would obey the 1/3-2/3 rule, the 300mm 1/2 and 1/2). None of this has huge relevance to actual photogaphy though. Its a shame the myth is so widely circulated as it means at some point you have to relearn everything, not to progress your photography, but just to ensure you aren't wrong.D3X then?That camera is a piece of pure awesomeness, used one for two jobs recently and the files are so clean and so sharp, as good as it gets without going medium format IMO, so much more of a joy to use than a hasselblad etc as well, lighter, faster and so on.Obviously the quality is still incomparable, but likewise I don't think there is another FF SLR that compares to the D3X out there right now.
JamesD, your secret is out.
Found a bit of an issue with the prime over the weekend, not that it wasn't there before: Zooming with your feet is all very well and good until the point at which you want to stand doesn't exist. I was at St.Bees and I either couldn't get far enough away to get the desired framing without running into a block or a chasm or something else.I'm guessing this is where the 1.6x crop factor becomes a bit more of a ball ache? and I'm guessing that wider primes cost $$$?(I also tried to battle the sun with my speedlights but soon realised it was a) futile and b) unecessary).
(I also tried to battle the sun with my speedlights but soon realised it was a) futile and b) unecessary).
