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09-23-2010, 10:31 AM   #31
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QuoteOriginally posted by violini Quote
I owned a Canon G11 before moving on to Pentax K-7. I've seen so many sample photos on the Internet taken with over thousand dollars lenses; these photos with partly sharp, partly blurred objects are really disturbing to me.
If that is what you want then sell the K-7 to me and buy a G11. What disturbs you is what is desired by most people who know how to use an SLR. The ability to CONTROL the amount of in and out of focus objects in a photo is why you buy a DSLR with a larger sensor and better glass. If you want everything to always be in focus go with a P&S with a small sensor.

09-23-2010, 11:17 AM   #32
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QuoteOriginally posted by steve1307 Quote
One of these?

Frazier Lens

I dont think it is available in a K-mount (or Canon/Nikon/Sony/Oly for that matter)
That is a freakin' awesome piece of tech. Wow. That down under fella knows his stuff.
09-23-2010, 12:04 PM   #33
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Troll?

QuoteOriginally posted by violini Quote
I owned a Canon G11 before moving on to Pentax K-7. I've seen so many sample photos on the Internet taken with over thousand dollars lenses; these photos with partly sharp, partly blurred objects are really disturbing to me.
I also believe this may be a troll. Or OP is particularly obtuse

Weighed in the balance, I favour troll.

YMMV
09-23-2010, 01:05 PM   #34
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Definitely Trolling.

QuoteOriginally posted by violini Quote
I owned a Canon G11 before moving on to Pentax K-7. I've seen so many sample photos on the Internet taken with over thousand dollars lenses; these photos with partly sharp, partly blurred objects are really disturbing to me.
Ok you must be trolling....

09-23-2010, 01:32 PM   #35
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QuoteOriginally posted by privateryan Quote
Ok you must be trolling....
Has 'Bokeh' become a 'thing' of some kind, is my question?

I worked in the business for years and never heard the word spoken aloud or much mentioned till the Internet.

Come to think of it, I *still* haven't heard the word spoken aloud,

(I do think that the OP is confused cause teeny-sensor cameras tend to lack appreciable OOF areas under many conditions unless you go out of your way to lock focus really short: it's easy enough to forget that some little feller like my old Lumix or a Canon G11 has the frame size of like a Kodak Disc. )
09-23-2010, 05:44 PM   #36
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Focal Length of the Eye

You can beg to differ, and the one web page does mention the change in focal length. If the focal length changes, then you can see from wide angle to telephoto, or something similar, hence changing the focal length. Your "field of view" and "angle of view" does not change. The focus distance does change as you look at subjects closer to you. The same thing happens with your camera as you focus on closer subjects. But instead of the lens moving, as happens in your camera, in the eye, the image plane moves, and the same effect is achieved.

You can calculate focal length at any distance, but typically the focal length is calculated when the eye/imaging system if focused at infinity (or some distance where it does not matter anymore as algebraic calculations do like infinity). By using a standard distance like infinity, the effect the imaging lens system has on the imaging system can be compared. However, I was mistaken about the actual focal length it is not 17mm, but about 22.3mm. See also the following:

Focal Length of a Human Eye


BD
09-23-2010, 06:23 PM   #37
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QuoteOriginally posted by BigDave Quote
You can beg to differ, and the one web page does mention the change in focal length. If the focal length changes, then you can see from wide angle to telephoto, or something similar, hence changing the focal length. Your "field of view" and "angle of view" does not change. The focus distance does change as you look at subjects closer to you. The same thing happens with your camera as you focus on closer subjects. But instead of the lens moving, as happens in your camera, in the eye, the image plane moves, and the same effect is achieved.

You can calculate focal length at any distance, but typically the focal length is calculated when the eye/imaging system if focused at infinity (or some distance where it does not matter anymore as algebraic calculations do like infinity). By using a standard distance like infinity, the effect the imaging lens system has on the imaging system can be compared. However, I was mistaken about the actual focal length it is not 17mm, but about 22.3mm. See also the following:

Focal Length of a Human Eye


BD
From your link: "The lens flexes to change its curvature and finish the focusing process. When an object is located at infinity, the focal length, or the distance from the cornea to the retina, of a normal relaxed eye is about 1.7 cm (17 mm).
"

The author specifically says at infinity, the focal length is about 17mm. If you change the curvature of a lens, you change its focal length. He doesn't explicitly state that the FL doesn't change. Unfortunately, in his explanation of how the eye focuses, he doesn't use the phrase "changing focal length" or anything like that. He does however, refer to changing the curvature of the lens. If this doesn't change the curvature of a lens, what does it do?

Focus is affected by the focal length, the image distance and the object distance. Since the eye itself does not change shape, the lens remains the same distance (the image distance) from the retina. If neither the focal length nor the image distance change, there is no change in focus. Sort of like a Brownie box camera. Since we all know that the human eye does, in fact, change focus, it must change focal length.

As for changing the field of view, the human eye has a FOV of almost 180 degrees. The small change in FL that I calculated would not significantly affect the FOV, so we wouldn't notice it. Besides, we hardly notice the things at the periphery of our vision anyway.

The relationship between FL, image distance and object distance is given by the formula in my last post. I have no reason to believe that it is invalid the human eye, just because it is organic, rather than glass. If the image distance remains constant and the object distance changes, the only variable left to change is FL.

Next time I go to my opthomologist, I'll ask her.

I just re-read your post before hitting submit. Are you saying that the retina (the image plane) moves? I agree that that would have the same effect, but I don't see anything in any of the links you posted, or any others I could find, that indicates that the retina moves.
09-23-2010, 08:43 PM   #38
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QuoteOriginally posted by VaughnA Quote
If that is what you want then sell the K-7 to me and buy a G11. What disturbs you is what is desired by most people who know how to use an SLR. The ability to CONTROL the amount of in and out of focus objects in a photo is why you buy a DSLR with a larger sensor and better glass. If you want everything to always be in focus go with a P&S with a small sensor.
Take for example: a photo of a strand of grapes, some in focus and the rest out of focus. What I want to see is the whole strand of grapes is the subject and should be in focus. Another example is shown in the lens review: The grasshopper head is in focus and the rest of the body is out of focus. These are what disturb me. I would think these are not equipment problem; most likely the photographer does not know how to handle the situation well.

09-23-2010, 08:51 PM   #39
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QuoteOriginally posted by violini Quote
Take for example: a photo of a strand of grapes, some in focus and the rest out of focus. What I want to see is the whole strand of grapes is the subject and should be in focus. Another example is shown in the lens review: The grasshopper head is in focus and the rest of the body is out of focus. These are what disturb me. I would think these are not equipment problem; most likely the photographer does not know how to handle the situation well.
Well, basically, if you have a K-7 and want to replicate what a P&S does, just shoot from further away and crop down to about the middle eighth of the frame, and there you go.

That's really all there is about these little cameras: they make a pretty nice image out of a teeny little chip of a sensor: if you want lots of DOF, they work just fine: it's if you want *less* that there's more of an issue. if you have a nice DSLR, you can basically just back off and make your own 'crop factor' ....by cropping.

('Bokeh,' by the way, usually refers to the subjective qualities of how an out of focus part of the image ends up rendered: thanks to various optical characteristics, these areas can look pretty, unobtrusive, or distracting, and that's why you hear people talk about it. In photography, we commonly want to isolate the subject from background clutter and whatnot to varying degrees: the quality of what this looks like can be of import. If you *don't* want any out of focus areas in your frame, then you want DOF, which is a function of distance focal length, and aperture. The size of the film or sensor also has a relationship to these when it comes to framing, ie, the angle of view, ...what may appear to be 'magnification' when you compare a framed shot to what the eye sees: A small-sensor camera like your G11 will almost always give great depth of field because the focal length of the lens will be very short to do a given job, but in some important ways this is almost the same as if you used a larger-sensor camera like your K7 and simply cropped out the middle of the frame. Follow?)

Last edited by Ratmagiclady; 09-23-2010 at 09:08 PM.
09-23-2010, 09:06 PM   #40
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Sorry I mis-stated what changes. I really have to stop the posts late at night! The curvature of the LENS actually changes (done by the eye muscles), and not the distance from the retina. Something we could never do in a camera, reshape a lens on the fly! So, since the lens to retina distance does not change, then the focal length by default.... you fill in the rest.

Have a good night!
09-23-2010, 09:21 PM   #41
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QuoteOriginally posted by BigDave Quote
Sorry I mis-stated what changes. I really have to stop the posts late at night! The curvature of the LENS actually changes (done by the eye muscles), and not the distance from the retina. Something we could never do in a camera, reshape a lens on the fly! So, since the lens to retina distance does not change, then the focal length by default.... you fill in the rest.

Have a good night!
Hee. Well, the human eye is trickier, because our brains build up kind of a real time picture from (usually a pair of) eyes that each is kind of always moving, so,sometimes I think the importance of the comparison is overstated: what's a 'true normal lens?' I dunno, binocular 43s? I think I like the short portrait lengths cause they most replicate for me 'Paying attention to something.'
09-24-2010, 02:14 AM   #42
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QuoteOriginally posted by violini Quote
most likely the photographer does not know how to handle the situation well.
Most likely you have no clue what a DSLR is for. Please sell your K-7 and buy a P&S. Oh, and never ever buy a DSLR again. Bye!
09-24-2010, 02:37 AM   #43
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Want no "bokeh" (never heard the word "bocca" before....) shoot at f10 and above, use a shorter lens, stand back and shoot.

Why am I entertaining this anyway?

Jason
09-24-2010, 06:24 AM   #44
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Violini,

The reason a lot of macro photos have shallow DoF is because when you get that close to a subject, your depth of field at a given aperture is almost non-existant. The photographer doesn't have enough light to stop down for a better depth of field, and even if they did, they'd hit the diffraction limit before they got the whole shot to be sharp. Focus-stacking is one way to avoid this.

To restate what others have said: Depth of Field (the lack or presence of Bokeh, if you will forgive my misuse of the term) is dependent on three factors.

1. Focal Length (Shorter focal lengths render more DoF, all other things equal)

2. Distance to Subject (closer to subject renders less DoF, all other things equal)

3. Aperture (Wider aperture gives less DoF, all other things equal.)

What you really want is a 4/3 or smaller SLR, or even a Point-and-Shoot. Because their sensors are smaller, the same field of view is done with a much shorter focal length. For instance, what your K-7 does with an 18mm focal length is what a basic P&S does with a 7.9mm focal length. Because of that, you'll get the same shot, but much more depth of field at the same aperture. This will allow you to get deep photos without stopping to oblivion ("Stopping to Oblivion" sounds like an awesome band name). This works in reverse, too: If you buy a medium Format camera, it's got a 50mm focal length to do the same job...much shallower DoF. This is why Medium and Large Format cameras are prefered for portraits.

Photography is subjective, and although I love me a nice shallow depth of field, to each their own.

As for the focal length argument: A lenses focal length does change from focusing, not just from zooming. Focal lengths (and f/stops) are quoted at infinity. What doesn't change is the effective focal length and the angle of view. I think.

This thread gave me eye strain.
09-24-2010, 09:51 AM - 1 Like   #45
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QuoteOriginally posted by violini Quote
brofkand, thanks for the link about hyperfocal distance.

The lens in the eye is a soft lens; the muscle can change the focal length instantly. That's why we can see objects near and afar.
This is an illusion. Most of what we perceive is information stored in the occipital lobe. A very small percentage of our visual field is currently being perceived.... most of it is constructed. When attention "snaps" from your finger to the mountain, both objects seem in focus because the old object of attention is stored in the occipital lobe and is combined with the new information coming in from the eyes.

Our eyes don't see... the occipital lobe at the rear of the brain does. The eyes take in visual information, which is grossly processed before perception occurs. Mose of the information in the periphery of our visual field is so blurry in nature, that if this processing was not happening, our visual field would be very small. However, when we look at a scene, we see a complete image edge to edge. The only time we experience the extent to which this is an illusion is when our attention does not pick up on an object in the periphery, the object moves, captures our attention, and suddenly appears.

For this reason, photography will never look like our perception, because it is an image that must be processed by attention. However, since the photograph is not three dimensional, our attention has the ability to focus on an area that is out of focus! And if you have everything in focus, the brain will NOT be able to isolate an object in the scene and pay attention only to that.

The art of photography is in capturing the real, but in a surreal way. Photography grabs items and directs our attention to it, and freezes action in a way that we could not otherwise perceive . A camera is not an eye, and any photograph is processed by 2 lenses, not one.

SOURCE: Biopsychology, 6th edition
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