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01/29/2006 03:15:24 PM · #1 |
Hello everyone :) !
First of all thanks a lot to the admins for the tutorial about DOF! Finally some documentation on something I've been looking for for ever lol :)!
Now the problem is that I tried out with my Fuji Finepix F700 digicam and didn't manage to get that DOF effect :(.
My compact digicam :) : //www.dcresource.com/reviews/fuji/finepix_f700-review/index.shtml
I don't manage to have the effect desired. My shots are either too dark or blurry :(.
Also I don't really know what Focus mode to choose: Center, Center Zone, Manual, Mobile, Auto?
I hope my question is correctly explained since my english is a bit rusty :(.
Thanks a lot in advance for your help :) |
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01/29/2006 03:29:03 PM · #2 |
First, that tutorial is a bit misleading in my opinion. Sensor size doesn't affect DOF -- the only things that affect DOF are aperture, focal length, and focal distance.
If you shoot a subject that is 10 feet away at 100mm at f/2.8, your DOF will be the same whether you use your camera, or a Canon 1dsmkII with a 35mm sensor.
The only difference arises when you need to compose the same way with a cropped sensor because this forces you to move away from your subject with the smaller sensor...thus increasing your distance to subject, and in-turn increasing your depth of field.
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Anyway, here's a little something I wrote a little while ago on the matter:
Full-frame sensors do not yield lower DOF when a subject is at the same distance. a lens: 100mm f/2.8 is 100mm f/2.8, no matter what the size of the sensor.The only things that affect DOF are the following: aperture, focal length, and focusing distance.
Take a Canon 1dsmkII and stand 10 feet from a tape measure, take a picture at 100mm f/2.8, now do the same thing with a Nikon d70...You will get 5.9 inches of 'acceptable sharpness' in both cases.
The only difference is when you want to frame (or compose) a photo exactly the same way -- with the smaller sized sensor of the D70, it becomes necessary, even when shooting at the same focal length to move away from your subject...thus resulting in the same picture, but a larger depth of field.
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People, when discussing full frame and DOF always seem to bring up the point and shoot cameras with their smaller sensors...I am using, for this discussion, a randomly selected camera: the Kodak Z740.The sensor on the Kodak Z740 is a type 1/2.5" sensor...which measures about 6mmx8mm. When compared to a film camera, or a full-frame DSLR, it is roughly four times smaller.
The Kodak Z740 has a focal length range of 38-380 (in 35mm terms) -- so people are confused when shooting at 38mm f/2.8 why their DOF is so small. The reason is that at 38mm, you'd technically be shooting at roughly 9mm f/2.8 -- which yields a DOF, when focused at 10 feet, of 29 inches to infinity. This is why it's impossible with these point and shoot cameras to get a nice DOF.
Furthermore, the f/2.8 aperture is also only available when zoomed all the way out. When you zoom all the way in (to a whopping 95mm (380mm equiv)), the minimum aperture changes to f/8 -- so that is why that even at the telephoto end (or 95mm, f/8) doesn't yield low DOF results either.
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In the end, you can see how the lense is the only thing ultimately responsible for depth of field, or how the photographer wants to compose the shot...the size of the sensor has nothing to do with depth of field.
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So, as you can see, that shallow depth of field just may not be possible with your camera...because your lens is actually just not able to open wide enough at any longer focal length. Good luck.
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01/29/2006 04:11:09 PM · #3 |
Originally posted by deapee:
The only difference arises when you need to compose the same way with a cropped sensor because this forces you to move away from your subject with the smaller sensor...thus increasing your distance to subject, and in-turn increasing your depth of field.
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And thus ... everyone is just saying the same thing, only in different words. :-)
The sensor size matters because you can't take the same shot on such a small sensor without either going with a wider angle lens (which forces greater DOF) or stepping back from the subject (which also forces greater DOF).
Does sensor size matter? Absolutely. But indirectly. Otherwise we wouldn't keep reading about how these P&S's can't get shallow DOF the way a DSLR can. :-) |
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01/29/2006 04:59:31 PM · #4 |
Originally posted by deapee:
First, that tutorial is a bit misleading in my opinion. Sensor size doesn't affect DOF -- the only things that affect DOF are aperture, focal length, and focal distance.
If you shoot a subject that is 10 feet away at 100mm at f/2.8, your DOF will be the same whether you use your camera, or a Canon 1dsmkII with a 35mm sensor.
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Your response, with all due respect, adds even more to the confusion, David.
The fact that has to be considered is that due to small sensor size, most if not all PS cameras ACTUALLY use VERY wide angle lenses, even at telephoto settings. With a small sensor, a 28mm lens is actually a telephoto, not a wide angle, but due to the rules of optics that you rightly mention, the depth of field is the same. Thus, since the image is cropped tremendously by the small sensor, depth of field is much greater for a small sensor than it is for a large sensor.
You are right, the sensor itself does not extend the depth of field. However, for the average user, it IS fair AND correct to say that because their camera has a small sensor, the optics are configured in such a way that depth of field for a given aperture is ALWAYS much greater than for a camera with a larger sensor.
That's not misleading at all, but to remove the sensor from the equation is very unfair to the guy that can't make heads or tails of why his f1.8 doesn't blur the background but so-and-so's 2.8 does.
The sensor IS involved. But to get it to fit, one needs to look at the ACTUAL focal length of their lenses - not the 35mm equivalent - to see what is going on. |
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01/29/2006 05:10:56 PM · #5 |
I respectfully disagree with both of you...
The size of the sensor has nothing to do with depth of field, great or small. It is all in the lens that sits on the camera -- in the case of the Z740, they TELL you that you're shooting at 38mm f/2.8, but the LENS itself is a 9mm f/2.8 -- whether you're shooting on a 100 foot sensor, or a 1mm sensor, 9mm f/2.8 is 9mm f/2.8.
Furthermore, I disagree with having FF gives more control over depth of field -- you just need to select the correct lens.
Shooting a subject at 10 feet with a 35mm sensor at 100mm and shooting a subject at 14 feet with a 1.5x sensor at 150mm will produce nearly the same DOF -- actually, the 1.5x sensor will yield you with .8 inches shallower DOF in that case.
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I don't see how I'm confusing anything -- if you are here to learn, you should learn the truth -- sensor size does NOT affect DOF -- and if that's your way around learning something properly, or you think that way of thinking suits anyone, then I'd have to begin to question anything that you say.
Sure, it's easier to think that way, but it's false, incorrect, and just flat out wrong. Remember, aperture, focal length, and focusing distance are the only things that affect depth of field -- in a real world. We'll leave the COC for another discussion...because I don't feel it's relevant enough and that would confuse more than is necessary.
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01/29/2006 05:31:21 PM · #6 |
Originally posted by deapee:
sensor size does NOT affect DOF |
100% correct --- that is, until you try to capture the same image on relatively different sized sensors.
Originally posted by deapee:
It is all in the lens that sits on the camera -- in the case of the Z740, they TELL you that you're shooting at 38mm f/2.8, but the LENS itself is a 9mm f/2.8 |
Yes! Now ask yourself WHY do they put such a tiny (i.e. short focal length) lens on the camera? Because a longer focal length lens would not let you fit the image on such a small sensor.
You already said it yourself "The only difference arises when you need to compose the same way with a cropped sensor because this forces you to move away from your subject with the smaller sensor...thus increasing your distance to subject, and in-turn increasing your depth of field."
So the size of the sensor DOES matter when it comes to taking EQUIVALENT IMAGES.
Let's say we shoot uncle Tom and fit him from head to foot on our sensor, then with a smaller sensor, we need either a wider angle lens, or a longer distance than what we would need on a larger sensor.
The size of the sensor does matter insofar as your ability to take identical images is concerned.
It's not incorrect to think this way. It's just a different way of stating the same thing.
And it's simply an easier way to explain to the newby why a P&S has a lot more DOF than does a DSLR. Is it wrong to explain it this way? Well, it's certainly not the complete story. But it's not inaccurate once you understand the design decisions being made (that a shorter focal length lens is necessary to fit the image on the sensor). What's really confusing is how the manufacturers keep touting their lenses in terms if "35mm equivalent". You gotta get that notion out of the newby' s head before he can understand why the DOF is different.
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01/29/2006 05:35:47 PM · #7 |
Originally posted by dwterry:
100% correct --- that is, until you try to capture the same image on relatively different sized sensors.
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Well, I made it that far and stopped reading because clearly you didn't read even my initial post where I clearly stated that in order to maintain the same composition on different sized sensors, with the smaller sensor it becomes necessary to change the camera to subject distance, which changes your focusing distance, and then in-turn results in greater depth of field.
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The main point is this (and this could have been gotten from my original post): There are three things that affect depth of field -- aperture, focal length, and focusing distance -- nothing more, nothing less (short of the circle of confusion, which, named-rightly, confuses things even more, but has little to no effect in the terms of this arguement).
EDIT: typo
Message edited by author 2006-01-29 17:36:36.
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01/29/2006 05:42:12 PM · #8 |
Originally posted by dwterry:
And it's simply an easier way to explain to the newby why a P&S has a lot more DOF than does a DSLR. Is it wrong to explain it this way? Well, it's certainly not the complete story. |
What's wrong with just simply explaining to a 'newby' exactly why there is a larger depth of field -- the way I did it -- because technically they're shooting at 9mm f/2.8 and not the stated 38mm f/2.8 (it is their crop factor that makes it an effective 38mm because the sensor isn't recording the full image)? I just don't understand why that is, even though it's easier to say 'well, it's a larger depth of field because your sensor is so small.' I think it would be best to just explain to them what is really going on and be done with it.
If we focused our time devoted to this thread on explaining exactly how it works and why it works that way, instead of arguing with eachother over semantics, then I think no one would be confused, and we could accomplish a lot more.
EDIT: more typos
Message edited by author 2006-01-29 17:43:42.
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01/29/2006 06:02:27 PM · #9 |
Originally posted by deapee:
Originally posted by dwterry:
100% correct --- that is, until you try to capture the same image on relatively different sized sensors.
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Well, I made it that far and stopped reading |
LOL! Well, that's obvious because in both of my messages I QUOTED YOU (the same words you just wrote again) and AGREED with you. :-)
Peace.
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01/31/2006 06:13:21 PM · #10 |
Thanks a lot for all your help :D !
Sadly I don't understand most of it since I don't have the correct vocabulary :( lol.
I'll print it and re-read it quietly at home lol (english isn't my native language so I try understand as well as possible lol :)).
Do you know a good site for photography beginners, with glossaries etc?
Thanks again for helping :D ! |
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