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Author Topic: Shallow DOF and Sony F828 Comparisonhttp  (Read 8864 times)
Lin Evans
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« Reply #40 on: March 13, 2005, 12:48:54 AM »
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I have a question: how much would it increase the price of the Sony F828 to give it a larger sensor, like the Cannons here, while keeping the camera the same in all other respects? One thing I realy like about the Sony is the design. Everything fits perfectly in your hand. For those who have never handled it, you should just to see how it feels. Although I haven't owned the high dollar digitals, I've held them, and nothing feels like that F828.

It's not possible. The lens determines the circle of definition. A lens like the one on the Sony F828 can only produce a circle of definition to fit the sensor designed for it. If a larger sensor were placed in image plane, then the circle of definition would still describe what it does with the Sony except you would have a circle rather than a rectangle of image.

In addition the aperture would be all wrong. As you may know from optical physics the lens diameter plays the major role in determining the amount of light striking the film or sensor plane, thus defining the maximum F rating. The small sensor allows the small lens (relative to 35mm) to achieve the equivalence of a very fast 35mm lens. With a large sensor it takes more light to achieve the same results.

It's just not possible to have a relatively tiny camera with a large sensor unless it also has a lens properly designed to match the sensor. The lens can be larger than necessary, and the additional circle of definition wasted as with crop factor dSLR's, but it can never be smaller than what is required to achieve the needed aperture.

In essence this simply can't work.

Best regards,

Lin
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Lin
Jonathan Wienke
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« Reply #41 on: March 13, 2005, 08:40:41 AM »
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howard smith
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« Reply #42 on: March 14, 2005, 08:44:08 AM »
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"Right, subject size has no influence on DOF."

Actually, it does in a rather indirect way.  You would not likely take a photograph of a dime (small subject) the same way you take a photograph of Half Dome (large subject).  Your choice of focal length lens and/or focus distance would be significantly different, producing profound effects on DoF.

That is why you can produce very noticible shallow DoF on the barbed wire fence but are having trouble with the marina.  Use the same focal length and focus distance in the marina as you did on the fence and you will get exactly the same DoF.  You just won't either get the boat in focus or much of the boat in the frame.
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dwdallam
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« Reply #43 on: March 14, 2005, 03:13:46 PM »
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"Right, subject size has no influence on DOF."

Actually, it does in a rather indirect way.  You would not likely take a photograph of a dime (small subject) the same way you take a photograph of Half Dome (large subject).  Your choice of focal length lens and/or focus distance would be significantly different, producing profound effects on DoF.

That is why you can produce very noticible shallow DoF on the barbed wire fence but are having trouble with the marina.  Use the same focal length and focus distance in the marina as you did on the fence and you will get exactly the same DoF.  You just won't either get the boat in focus or much of the boat in the frame.
haha yeah exactly. Well, I REALLY want to do large subject shallow depth, but I guess I'll have to find other things to do with the F828. Do you think that add on lens that screws on like a filter would help? Still don't understand how a wider angle will help shallow DOF.
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dwdallam
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« Reply #44 on: March 09, 2005, 10:47:34 PM »
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Guys, I feel like my posts are being hijacked for a technilogical discussion each time I post anything on DOF. For that reason, I'm starting a DOF specific thread. Please post technilogical discussions and arguments there. Thanks
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didger
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« Reply #45 on: March 11, 2005, 03:40:19 PM »
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Would selectively sharpening a digital image increase the DoF? Sharpen the just the edge of the DoF range, both just inside and out side.
I've never tried it or even thought about it before. Any ideas?
I HAVE tried essentially this using the PKSharpener Creative sharpening tool, and yes, you can selectively sharpen areas in an image and you can feather the effect, though I've never really considered that a form of increasing DOF, though I suppose you could look at it that way.  However, any kind of sharpening only gets you a rather minimal effect before sharpening artifacts rule the day (or is that ruin the day?).  Serious image blurring isn't just a matter of fuzzy edges that you could sharpen, but substantial information loss.  You can digitally throw away information in various clever, creative, and visually useful ways, but you can't fake information that's missing altogether, alas, whether the information is missing because of lack of lens or sensor resolution or due to black shadows or blown highlights.
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DiaAzul
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« Reply #46 on: March 11, 2005, 07:04:36 PM »
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Here are a couple of narrow depth of field pictures...not boats, but will give some examples of how DOF can be affected.

First is Canon EOS10D, approx 150mm and f2.8



Second is Canon EOS1DII, approx 25mm and f4



Final image is Canon EOS1DII, 17mm all image is in focus (nearground to background), however, processed with Photoshop CS lens blur filter to simulate narrower DOF (NB this is a quick and dirty example, with more work the effect can be blended in more naturally)


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David Plummer    http://photo.tanzo.org/
Jonathan Wienke
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« Reply #47 on: March 12, 2005, 10:36:34 PM »
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I'll do some more digging through the archives, and see what I can come up with...
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Lin Evans
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« Reply #48 on: March 13, 2005, 10:13:20 AM »
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Well, have you seen the F828? It's not a small camera. But more importantly, what I meant was I wonder how much more expensive the F828 would be if they could make it with a large sensor and matching fixed lens, as in 28-200mm Ziess lens it has now. In other words, I wonder what they could do pricewise to have the same design camera work with a large sensor?

Yes, I've had an F828 since they became available. If you designed a similar camera with a large sensor it would be the average size of existing cameras with large sensors. The Canon 350D represents about as small of a camera body as will accommodate a 1.6x crop factor sensor. So if you can imagine a camera with a lens about the size of a Canon 70-200 L attached to the body of a Canon 350D then you will be somewhere close to what it would take. To get the F828's lens speed in a large sensor camera would require a lens with an objective of around 77 mm. To get the zoom would require a length similar to the 70-200 and would probably cost in the neighborhood of $4000. It's doubtful that anyone would buy it because the lens itself would weigh over three pounds.

In short, it won't happen and would be totally impractical...

Best regards,

Lin
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Lin
BJL
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« Reply #49 on: March 14, 2005, 11:50:34 AM »
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the size of the subject is inconsequential.
For all practical purposes, subject size has big consequences. Look at how limited the DOF is in macro photography even when stopped well down.

Beware of comparisons got by changing just one variable in a particular formula which thus introduces the assumption the constancy of the particular collection of other quantities used in that formula. I can easily create different mathematically equivalent formulas that use a different collection of quantites and seem to give quite different conclusions if not interpreted carefully. For example, there are valid DOF formulas that make no mention of focal length, or no mention of f-stop, or no mention of subject distance, or even no mention of CoC; the last one should be very popular!
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Lin Evans
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« Reply #50 on: March 14, 2005, 01:32:36 PM »
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One of the best definitions I've ever heard for describing COC (circle of confusion) is:

"A group of professional photographers sitting in a circle discussing depth of field...."

These arguments are primarily difference in semantics rather than differences in substance. The original question concerned the Sony F828 and whether it was "possible" to get a blurred background when shooting a large boat. The answer is yes, it's possible but certainly not "practical". I could connect my F828 to my Swarovski ST-80 HD or my Meade ETX-90 - shoot from 1000 yards at F14 and produce a blurred background. But in the practical sense of using the camera wide open and shooting from a distance allowable within the native focal length for a reasonable frame it's just not practical. The small sensor and associated lens produces a 35mm "equivalency" of 28-200 mm at an "equivalent" aperture. In reality the true focal length quite wide angle and the stated aperture must be multiplied by about four to get a 35mm equivalency. So the F2.8 actually has the optical 35mm characteristics of about F11 while F8 has the optical 35mm equivalence of F32. This is one reason I love the F828 for shooting small, highly detailed fine art macros with this camera. I can shoot hand-held in available light or even with built in flash and get results which are difficult to achieve in the studio with my Canon EOS-1DS, a tripod, specialized lighting, an expensive macro lens and lots of "luck".

It's just not a camera designed for producing a background blur type image and any attempt to make it perform that way simply leads to frustration. It's "horses for courses" and the F828 is a great tool for what it does well.

Best regards,

Lin
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Lin
AJSJones
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« Reply #51 on: March 09, 2005, 11:28:17 PM »
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So, what's the question again?
Have you decided what size you want to print and how far away you are going to view the prints?  Sorry, but as has been pointed out, the rest of the determination of DoF is mathematics or optics but there's no philosophy there.  There may be certain boundary conditions, based on physical science and what can reasonably be manufactured , that could be summarized in inexact generalities, such as "cameras with small sensors usually have difficulty creating shallow DoF" .  These are not philosophical statements, however.
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howard smith
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« Reply #52 on: March 11, 2005, 03:17:08 PM »
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"Now the pity is that there's no way to fake MORE DOF than what you shot."

Perhaps there is.  DoF is the zone of "perceived in-focus" image, the part of the image that is acceptably sharp.  Would selectively sharpening a digital image increase the DoF?  Sharpen the just the edge of the DoF range, both just inside and out side.

I've never tried it or even thought about it before.  Any ideas?
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howard smith
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« Reply #53 on: March 11, 2005, 04:43:47 PM »
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You want fries with that?
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howard smith
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« Reply #54 on: March 12, 2005, 09:52:08 AM »
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Sorry you were offended by my comments about your depth of field effect.
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dwdallam
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« Reply #55 on: March 13, 2005, 01:54:19 AM »
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Also, I'm really interested in what Howard suggested, but I don't know what a WA filter is.

Here's a picture I took a few days ago. I didn't have it in macro mode, and I forgot the settings. but it shows how the F828, given a very close subject, can produce some shallow DOF. Surprised me:
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dwdallam
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« Reply #56 on: March 13, 2005, 02:21:50 PM »
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dwdallam, a wide angle "filter" isn't really a filter, but a supplementtal lens that goes on like a filter.  It simply proves a wider angle of view.

The F828 can produce narrow DoF as you show.  But the field of view isn't enogh there to fit in a 60' boat.

The F828 doe not have a 28-200mm Ziess lens it has now.  Thta is the equivalent 35mm focal length.

DoF is determined the same way for the F828 as it is for an 8x10 view camera.  I suggest you learn how that is done and go from there.  You sound frustrated.  Learning what your camera can and can't do may help.
I am learning what my camera can and can't do Howard. Have you been reading this thread? (lol)

What I don't understand is how a wider angle lens will give me better shallow DOF on large subjects?
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howard smith
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« Reply #57 on: March 14, 2005, 01:10:30 PM »
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Lin, what you say is partly true.  Where the subject falls within (or outside for that matter) the DoF has nothing to do with DoF.  But in practicle terms, most photographers (not even me) set the focus distcance and f/stop and then look for an "in focus" subject.  Most photographers select a subject, compose, focus, decide what the DoF should be, set the f/stop, shutter speed and shoot.  So, for practicle considerations, size matters.  Large subjects will require a wide lens and/or a long focus distance (if the photographer wishes the subject to be within the frame and focused).  You simply will not get a full body portrait of a 6' tall person with a 500mm lens on a 35mm camera from 10'.  NowI suppose you might argue that the only propblem is teh model is standing in the wrong place, but not practicle.  True, if that is all the camera I had, I would ask the model to walk down the block.

DoF is not determined by sensor size - directly.  Look at the equations for DoF and point to the term for sensor size.  Not there.  Now you could say that if I selected a 20x24 camera instead of a 35mm for the above example, I might get what I wanted.  But that isn't a practicle method either.  I usually won't set the model and tripod up and then decide which camera to use.

Another question here.  If I set up a shot with an X-Pan camera (focus distance, f/stop, lens) and then switch from regular to panorama mode, does the DoF change?  If you say yes, you would of course be wrong.  I could then have the film processed, cut the frame in half and change the DoF back again.
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dwdallam
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« Reply #58 on: March 15, 2005, 05:11:44 PM »
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I am still interested in what some of you can come up with, however, given my parameters. I looked at some professional boat photography sites, but none had what I was looking for. Is it even possible?
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