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DPChallenge Forums >> Tips, Tricks, and Q&A >> Digital Cameras vs. Apertures (Question)
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01/14/2005 06:52:57 PM · #1
Apparently when you use a aperture of 2.8 it would give a shallower depth of field than an aperture of 16.0.

The question I have is,
Does that happen with digital cameras, or does the aperture only change the amount of light entering the camera?

The reason I ask is that I have never found that the aperture made any difference to the depth of field in the photos I have taken. I currently own a Nikon Coolpix 8700 with apertures of 2.8 to 8.0
01/14/2005 06:57:40 PM · #2
To over simplify, it happens with all cameras.
01/14/2005 07:03:19 PM · #3
It happens with all cameras, as stated above. I've never been able to get the desired shallow depth with my s5100 or my dsc-p52 like I can with my 300d even with only the kit lens and f 5.6. If you really want a SHALLOW depth of field and I mean millimeters matter, you'll have to get a DSLR and like a 50mm 1.4 lens. Or like a 300mm 2.8 etc.
01/14/2005 07:24:18 PM · #4
This was being discussed earlier in another thread.

I will repeat a scap of what I said there. The nature of the lens is inherent. It has certain properties based on mathematical equations that will not, can not change, no matter what camera it is applied to.

The focal length of a lens will however determine how much DOF you will get. A wide angle lens at any given f/stop has a far greater DOF then a tele set at the same f/stop. Therefore any DOF effects, such as bokeh, are very hard to discern, if they are noticeable at all, with a wide angle.

The min. focal length on your Coolpix is only 9mm. That is extreme wide angle. At that zoom setting you should notice no DOF effects at all. In fact if your subject is ever more than 3 feet from the lens you don't even have to focus.

At the far end your camera will zoom to about 70mm. That is mid range bewteen what is called a normal lens and short telephoto. At this zoom setting you will notice some DOF effects, but nothing extreme.

Message edited by author 2005-01-14 21:51:24.
01/14/2005 10:24:26 PM · #5
Originally posted by deapee:

It happens with all cameras, as stated above. I've never been able to get the desired shallow depth with my s5100 or my dsc-p52 like I can with my 300d even with only the kit lens and f 5.6. If you really want a SHALLOW depth of field and I mean millimeters matter, you'll have to get a DSLR and like a 50mm 1.4 lens. Or like a 300mm 2.8 etc.

Here's a couple of shots with a fairly shallow DOF shot with a P&S camera ...

' . substr('//images.dpchallenge.com/images_challenge/141/thumb/38922.jpg', strrpos('//images.dpchallenge.com/images_challenge/141/thumb/38922.jpg', '/') + 1) . ' ' . substr('//images.dpchallenge.com/images_challenge/186/thumb/58793.jpg', strrpos('//images.dpchallenge.com/images_challenge/186/thumb/58793.jpg', '/') + 1) . '
01/15/2005 12:05:52 AM · #6
What i see there is an out of focus foreground - the background is in focus in both pics all the way back.
Due to the small sensors in all but dSLRs the DOF is extreme.
' . substr('//images.dpchallenge.com/images_portfolio/16648/thumb/133945.jpg', strrpos('//images.dpchallenge.com/images_portfolio/16648/thumb/133945.jpg', '/') + 1) . ' is an expampe of shallow DOF - my head is just behind my daughter's head, to DOF is what, 8 inches or less?
' . substr('//images.dpchallenge.com/images_portfolio/16648/thumb/133954.jpg', strrpos('//images.dpchallenge.com/images_portfolio/16648/thumb/133954.jpg', '/') + 1) . ' Here the bookcase is about 3 or 4 feet behind the kids. both pics are with a dRebel. I could never get this kind of DOF/effect with my Fuji 602. Beleive me, i tried. Only in macro could i come close.
01/15/2005 12:39:49 AM · #7
All other things being equal, depth of field decreases with a bigger sensor size. So yes, a larger aperture (smaller f-stop) will give less depth of field, but it is harder to get shallow DoF with a small sensor camera.

It is certainly easier with a SLR sized sensor.
' . substr('//www.pbase.com/gordonmcgregor/image/15544940/small.jpg', strrpos('//www.pbase.com/gordonmcgregor/image/15544940/small.jpg', '/') + 1) . '

Depth of field also decreases as the subject to camera distance decreases, so if you get in close, you can get shallower DoF.
01/15/2005 12:42:35 AM · #8
Originally posted by Gordon:

All other things being equal, depth of field decreases with a bigger sensor size. So yes, a larger aperture (smaller f-stop) will give less depth of field, but it is harder to get shallow DoF with a small sensor camera.

It is certainly easier with a SLR sized sensor.
' . substr('//www.pbase.com/gordonmcgregor/image/15544940/small.jpg', strrpos('//www.pbase.com/gordonmcgregor/image/15544940/small.jpg', '/') + 1) . '

Depth of field also decreases as the subject to camera distance decreases, so if you get in close, you can get shallower DoF.


IMG_0409.jpg
Canon EOS D60
1/2s f/2.8 at 100.0mm (35mm equivalent: 697mm) iso100 full exif
is under teh above pic. What lens/lens set up? You list 100mm, then 35mm= of 697?
(good example of DOF though)
01/15/2005 12:43:00 AM · #9
Originally posted by Gordon:

All other things being equal, depth of field decreases with a bigger sensor size. So yes, a larger aperture (smaller f-stop) will give less depth of field, but it is harder to get shallow DoF with a small sensor camera.

It is certainly easier with a SLR sized sensor.


Not! The size of the sensor has zero to do with DOF.
01/15/2005 01:11:03 AM · #10
Originally posted by nsbca7:



Not! The size of the sensor has zero to do with DOF.


Please read some correct info...
//www.wrotniak.net/photo/dof/
The simplified version with a more practical application
//www.photo.net/learn/optics/dofdigital/
01/15/2005 01:21:00 AM · #11
In a nutshell, fate and gordon are right; effectively, DOF decreases with a larger sensor. Why? because it takes a longer focal length lens to cover the same angle of view when the sensor (or film) is bigger. 90mm on 4x5 view camera roughly equals 28mm on 35 mm SLR. So for the same angle of view, and the same aperture, the smaller sensor shows an image with more depth of field. This is correct.

Another thing to consider is that aperture is defined as the ratio of physical diameter of the aperture to focallength of the lens. So a 25mm aperture on a 50mm lens is f:2.0... The same exact hole in a 200mm lens is 5:8.0... Great depth of field coems from very small physical apertures, which reduce the size of the circle of confusion dramatically. The use of such tiny apertures on extreme telephoto would, in fact, increase their DOF dramatically, but at the expense of extremely long exposure times, an unacceptable tradeoff.

Robt.

01/15/2005 01:25:37 AM · #12
Originally posted by Prof_Fate:



IMG_0409.jpg
Canon EOS D60
1/2s f/2.8 at 100.0mm (35mm equivalent: 697mm) iso100 full exif
is under teh above pic. What lens/lens set up? You list 100mm, then 35mm= of 697?
(good example of DOF though)


Another one of the quirkier aspects of pbase, along with being broken for the last month or so. They've never calculated 35mm equivalents correctly. It was shot with a 100mm f2.8 macro lens.
01/15/2005 02:04:22 AM · #13
Originally posted by Prof_Fate:

Originally posted by nsbca7:



Not! The size of the sensor has zero to do with DOF.


Please read some correct info...
//www.wrotniak.net/photo/dof/
The simplified version with a more practical application
//www.photo.net/learn/optics/dofdigital/



All right, this is gobaldygook.

These sites are skewed. No BS.

This is a quote from one: Using the same lens on a EOS 10D and a 35mm film body, the 10D image has 1.6x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)


I would say it would be a different image, but only because one sensor would be bigger than the other thus at the same rate of enlargement one image would be bigger than the other. The the subject of both images would be exactly the same size but the image that came from the smaller sensor would apear to be cropped. Becasaue it was by the smaller sensor.

The authors of both these articles are compareing specs of lenses "as if they acted like" certain lenses on other cameras. This is confusing terminology that they are useing because they are mixing givens with "acts likes". And it seems to obviously be confusing many people.

Characteristics of a lens such as aperture, DOF and focal length are products of a mathematical equation that do not vary just because you bought a Sony with X size sensor and your friend bought a Nikon with Y size sensor. All the sensor size does is determine what your crop factor (how much of the edges of the image are cut off) is. They in no way affect any of the properties of the lens.
01/15/2005 02:25:38 AM · #14
Of course I am talking about using the same exact lens on two different cameras.

If the equation were to change, say by using a point and shoot with an effective 200mm zoom as opposed to a 1Ds with a 200mm EF lens then yes. The point and shoot would have much more depth of field. Why? Because the lens on the point and shoot may be the equivalent of a 70mm if mounted on the 1Ds. So the point and shoot would have much deeper DOF then the 1Ds at this point, but it would have an Identical DOF as the 1Ds with a 70mm lens if they were set at the same f/stop.

The key word is effective.

Message edited by author 2005-01-15 02:57:06.
01/15/2005 02:54:26 AM · #15


Another thing to note: If the distance from the lens to the film plane (sensor) were to change this would cause all all the numbers to change. That is why a 200mm on a 6x7 camera has a much differnt DOF then the same 200mm on a 35mm.


Message edited by author 2005-01-15 02:56:18.
01/15/2005 10:59:31 AM · #16
A lot of the confusion on this issue is due to the fact that the camera manufacturers give 35mm equivelent ratings for the point and shoot lenses. A 33-96mm 35mm equivelent lens on a point and shoot camera is actually something like a 7-28mm lens in reality, so it gives you a much greater DOF.
Mark
02/23/2005 04:50:17 PM · #17
Originally posted by scroosloose:

A lot of the confusion on this issue is due to the fact that the camera manufacturers give 35mm equivelent ratings for the point and shoot lenses. A 33-96mm 35mm equivelent lens on a point and shoot camera is actually something like a 7-28mm lens in reality, so it gives you a much greater DOF.
Mark

I was jus wondering if there is anybody that can give me any insight on this particular post. how do figure out on the cameras with zoom lenses what the real focal length is? i thing some one said you times it by .6 but iam not sure thanks
Leon
02/23/2005 04:58:35 PM · #18
The "real" focal length range is usually written on the lens. On my camera, 8.9 71.2 mm.

The other numbers are the "35mm equivalents", and they are ONLY discussed because they give a point of reference with which many people are familiar. On a 4x5 inch view camera, 90mm is wide angle lens. It's roughly equivalent to a 28mm lens on a 35mm camera. Angle of coverage is essentially determined by the size of the film or the sensor. Take a piece of 35 mm film and place it on the film plane of the 4x5 view camera, and that 90mm lens just became, effectively, a mid-range telephoto, since the film is "cropping out" a mUCH smaller central portion of the image.

Robt.
02/23/2005 05:01:36 PM · #19
Originally posted by bear_music:

The "real" focal length range is usually written on the lens. On my camera, 8.9 71.2 mm.

The other numbers are the "35mm equivalents", and they are ONLY discussed because they give a point of reference with which many people are familiar. On a 4x5 inch view camera, 90mm is wide angle lens. It's roughly equivalent to a 28mm lens on a 35mm camera. Angle of coverage is essentially determined by the size of the film or the sensor. Take a piece of 35 mm film and place it on the film plane of the 4x5 view camera, and that 90mm lens just became, effectively, a mid-range telephoto, since the film is "cropping out" a mUCH smaller central portion of the image.

Robt.


Thanks
02/23/2005 08:43:20 PM · #20
Originally posted by damelzakelly:

Apparently when you use a aperture of 2.8 it would give a shallower depth of field than an aperture of 16.0.

The question I have is,
Does that happen with digital cameras, or does the aperture only change the amount of light entering the camera?

The reason I ask is that I have never found that the aperture made any difference to the depth of field in the photos I have taken. I currently own a Nikon Coolpix 8700 with apertures of 2.8 to 8.0


Doesn't anybody know how to use google or pick up a book to find out these very simple questions?
02/23/2005 09:39:30 PM · #21
Originally posted by MeThoS:

Doesn't anybody know how to use google or pick up a book to find out these very simple questions?


Perhaps not... but then again, who are we to judge.

What seems simple to you, could quite readily seem unsurmountable to another. One can never assume that others know what he or she does... as we are all ignorant to varying degrees.

Just a different point of view...

Ray

Message edited by author 2005-02-23 21:45:24.
02/23/2005 10:36:22 PM · #22
Originally posted by MeThoS:

Originally posted by damelzakelly:

Apparently when you use a aperture of 2.8 it would give a shallower depth of field than an aperture of 16.0.

The question I have is,
Does that happen with digital cameras, or does the aperture only change the amount of light entering the camera?

The reason I ask is that I have never found that the aperture made any difference to the depth of field in the photos I have taken. I currently own a Nikon Coolpix 8700 with apertures of 2.8 to 8.0


Doesn't anybody know how to use google or pick up a book to find out these very simple questions?


To describe this question as simple is at best condescending. nsbca7 and bear_music are professional photographers, yet they don't exactly agree on this subject, do they? Of course we know how to use google, and we know how to pick up and read books, but that doesn't mean we should be opposed to a simple conversation about a subject that confuses us.

Please don't be so insulting. I was baffled about this for years, and yes, I found my answer on the web, but not on DPC. I'm very glad to see it being discussed here, as this makes it much EASIER for other curious folk to find.

These are open forums. Please don't ever discourage the asking of questions. It's how many people prefer to learn.

Thank you to all who have contributed, even though I disagree with one of you :)
02/23/2005 10:45:38 PM · #23
Originally posted by nards656:

...Thank you to all who have contributed, even though I disagree with one of you :)


Please say it isn't me... I would be so hurt.

Just kidding my friend. I for one did not find the question silly. Silly would be when you already know the answer but ask the question anyway. As you stated, this is a learning venue... and sometimes what may seem as the essence of simplicity, may, to someone like myself, seem insurmountable.

Have a great day, and happy shooting.

Ray
02/24/2005 02:21:56 AM · #24
Originally posted by nards656:


To describe this question as simple is at best condescending. nsbca7 and bear_music are professional photographers, yet they don't exactly agree on this subject, do they?


Just a note:

I'm an amatuer.

Added note: I do agree with the rest of what you posted. (so far)

Message edited by author 2005-02-24 02:29:24.
02/24/2005 03:04:44 AM · #25
DOF is actually independent of focal length. They have nothing to do with each other. DOF is a function of the physical diameter of the aperture in the camera. The larger the physical aperture, the less depth of field.

An f-stop number is a ratio; it's the ratio of the physical diameter of the aperture to the focal length of the lens. Like this: on a 24mm lens, f:4.0 would be a 6mm aperture. On a 200mm lens, f:4.0 would be a 50mm aperture. Therefore, the 200mm lens shooting at f:4.0 has significantly less DOF than the 24mm lens at f:4.0, because the physical diameter of the aperture is so much larger. For the 200mm lens to have the same DOF as the 24.mm lens does when it is stopped down to f:4.0, the 200mm lens would have to be stopped down to a 6mm physical aperture, which would be f:33.33 (200mm divided by 6mm = 33.33).

That DOF is independent of how "wide" a lens is can be proven with a comparison between a view camera negative and a 35mm negative; mount a 90mm lens on the 4x5 and shoot a negative at f:8.0, then measure out a 35mm film-sized section from dead center and print that at 8x10. Now shoot the same scene or setup with a 35mm camera mounted with a 90mm lens set at f:8.0 and print an 8x10 of that. Differences of film grain aside, the images will be indistinguishable.

The reason a "wide angle" lens is perceived to have "more DOF" than a "telephoto" mounted on the same camera is a function of the fact that a given f-stop on the "shorter" lens is physically smaller than the same f-stop on the "longer" lens.

This is not conjecture, it's not disputable, it's a simple fact. There are other optical considerations that come into play with modern, compound lenses, but these fundamentals always hold true.

Since this is true, you might well ask "Why don't we show the actual size of the aperture instead of the f-stop ratio on our lenses?" That's a good question, and the answer is simple; light falls off in brightness proportional to the square of the distance it must travel. Therefore, a "shorter" lens will deliver the same amount of light to the film (or sensor) plane with a smaller aperture (less light enters the lens, but there is less falloff) than will a "longer" lens. Therefore the ratio is important, because it allows accurate metering; the physical size of the aperture is meaningless for metering purposes all that matters is the amoung of light that reaches the film plane.

One more thing; the proof of what I'm saying, essentially, is built right into your zoom lenses; notice that when they are zoomed in your maximum aperture may be, say, f:3.5, and when they are zoomed out you will find that the maximum aperture you can accomplish is, say, f:5.6. This is because the physical size of the aperture is not changing, but the focal length of the lens is, and so the ratio is changing, and so is the amount of light that physical aperture is able to deliver to the film plane.

Robt.
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