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Opinion Summary
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Pentax *istD Digital SLR Camera
by dkozin | Jul 26 '04
Pros: Solidly built, SLR, easy manual zooming/focusing, TIFF/RAW, picture quality
Cons: No 640x480 resolution, no ISO100 setting, slow image writing, solid disc for menu control
Return to opinion
OVERALL RATING
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Date Written |
eBay and small pictures (Reply to this comment)
by iceblinker
eBay and some other sites like Photobucket now automatically resize pictures as they're uploaded - so Pentax's minimum picture size is rarely a hassle.
It's often good to do some cropping first anyway for eBay items.
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Mar 23 '07
12:55 pm PDT
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Polarizers (Reply to this comment)
by iceblinker
A circular polarizing filter also needs to be rotated to get the optimum effect - so no advantage with a rotating front element.
A linear polarizer has much more effect (particularly on reflections) and one seems to work OK with my DS. The autofocus and meter seem unaffected - although maybe I've just been lucky so far.
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Mar 23 '07
12:52 pm PDT
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Chip size (Reply to this comment)
by iceblinker
Is the D's sensor chip larger than the DS's? A 35mm frame is about 1.4 times larger than the *ist DS's. (Some say 1.5). That's not what I call "close in size".
Yes it means there is less choice of ultra wide angle lenses, but the advantage of being able to use much smaller, lighter and cheaper lenses for telephoto is wonderful. This also means that shallow depth of field for telephoto is easier to obtain and more affordable - since shorter lenses tend to be faster than longer ones.
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Mar 23 '07
12:50 pm PDT
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dkozin is right (Reply to this comment)
by ricehigh
Play with this Depth-Of-Field (DOF) online calculator and you will find that the DOF increases as frame size decreases, for the *same* 135 equivalent focal length, i.e., the actual Angle-Of-View (AOV).
http://www.dofmaster.com/dofjs.html
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Jan 24 '05
1:53 am PST
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Re: Howard is right (Reply to this comment)
by dkozin,  in Electronics
Not to beat a dead horse, but can you explain then why with my Panasonic FZ1 it is impossible to blur the background at wide angle even at f/2.8, whereas with this Pentax I can easily blur the background (also at wide angle) even at f/4?
Obviously, it is because the lens's focal length is vastly different. At wide angle, my Panasonic FZ uses real focal length of 4.6mm, whereas this Pentax has (in my case) focal length 18mm. Nobody disputes that the DOF (and ability to blur the background) depends on the focal length and the aperture used. However, it is the sensor size (be it CCD or CMOS) that dictates the use of certain focal length.
A couple of posts below, you will see what Michael Reichmann at Luminous Landscape (http://www.luminous-landscape.com/about/contact.shtml) responded regarding this.
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Dec 31 '04
8:51 am PST
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Howard is right (Reply to this comment)
by colonialpara,  in Electronics
and I think this re-review needs a re-write to eliminate the points of confusion still not addressed. At the end of your review, you still talk about DOF being a function of CCD size. This is NOT the case. If you re-write, let me know and I'll re-rate this review.
Paul
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Dec 30 '04
7:22 am PST
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Re: Re: Re: Re: Re: Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by ricehigh
I list the prime facts and factors as follows:-
1. DOF depends only on focal length and aperture selected at that particular focal length (which Howard mentions);
2. Wider focal length has a deeper DOF or vice versa, i.e., longer focals have a shallower DOF (which dkozin mentions);
3. Smaller sensor size requires shorter focals to maintain the same FOV (Field Of View or simply the "Angle Of View").
Thus, it's very simple that we have:
Smaller Sensor => Shorter Focal => Deeper DOF provided that FOV is the SAME.
After all, since that the case is so simple, why "guru" need to be asked or to quote their words? ;-)
To make the case even more clear, my conclusion is that dkozin's observation is correct from the very beginning and Howard is also correct for the mentioned factor above. However, he overlooks the combined results is that one can't have the same focal length to shoot and compare with for sensors of different size as the FOVs are different in practical terms.
Thus, the final outcome is that when we have DC which has very small sensor size, we cannot have "blurred" background owing to the already very deep DOF, even the lens is set at wide opened. That's also one of the big reasons why professional photographers for advertising jobs etc. prefer the use of medium film format camera so as to get shallower DOF in their works.
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Aug 30 '04
7:44 pm PDT
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Re: Re: Re: Re: Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by dkozin, in Electronics
I never said that the CCD can be used without a lens at all. THis is exactly my point - different size of CCD requires different lens to produce same angle of view.
Yes, it is the lens that makes DOF different. But the kind of lens you have to use depends on the physical size of CCD.
You might not see my point (although I think I present it clearly), but at least others do.
Email to Michael Reichmann at Luminous Landscape (http://www.luminous-landscape.com/about/contact.shtml):
"Michael,
I would like to ask you a question: Is it true that the physically larger CCD gives one more control over DOF (e.g. the larger the CCD, the longer lens is required to have the same angle of view and thus it is easier to get shallower DOF)?
Thank you for your time!"
Response
"Yes, this is correct.
Michael"
I have a second email (from J. Andrzej Wrotniak, authour of the article I was quoting here) that agrees with me
You may keep insisting I am incorrect (based on the fact that I am not a professional photographer). However, 1. this is a matter of simple geometry and 2. as long as Michael Reichmann and J. Andrzej Wrotniak tell me my understanding of this is correct, I will believe it is.
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Aug 03 '04
7:28 am PDT
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Re: Re: Re: Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by Howard_Creech, in Electronics
1. Ironically, the articles and quotes you supplied support the fact that depth of field (how far the plane of focus extends in front of and behind the point of focus) is a property of the focal length of the lens and the aperture (as I originally explained) rather than a property of the size of the CCD---so I will just move on to clarify any confusion others may now have after reading this comment exchange. Below is some of the material you referenced:
Also, from http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml
"A common complaint about digital cameras is that when using one it's not possible to get nice out-of-focus backgrounds. Why therefore do digital cameras have greater Depth of Field? The reason for this is that the imaging chips on most consumer digitals is very small, around the size of ones smallest finger nail. This means that a normal lens for a format that small is as short as 15mm. A 15mm lens at f/5.6 has Depth Of Field from about 2.5 feet to infinity. Not too much opportunity for selective focus, is there?
2. For anyone who may have been reading these comments and has now become confused, I discussed this with my friend (former professional photographer, photojournalism degree & 16 years selling photo/optics) and he suggested a test to demonstrate that depth of field is a property of focal length of the lens and aperture rather than a property of the size of the CCD sensor.
Take two digital cameras, a Nikon D70 dSLR (which has a large CCD sensor) and an Olympus C5060Z (which has a smaller CCD sensor) –remove the lens from the D70—you would have to cut the lens off the C5060Z since it cannot be removed- so you can just visualize the C5060Z without a lens.
Now set up a small table with a white cloth covering the surface, place anything you like on the table (my friend suggested a vase of colorful flowers) and photograph the scene from up close with both “optics free” cameras. Review the image files from both cameras.
Here’s what you’ll see---a confused mass of color blobs with no definition whatsoever, and the only difference between the two image files will be their size.
Why won’t the image files show anything recognizable? Because the lens resolves the image and focuses it on the CCD/CMOS sensor which is the recording medium-- without a lens to resolve the image it is impossible for the CCD/CMOS sensor to record anything recognizable.
You won’t notice any difference in depth of field between the two images---- BECAUSE THERE WON’T BE ANY DEPTH OF FIELD WITHOUT A LENS TO RESOLVE AND FOCUS THE IMAGE
3. No one expects you to be an expert on digital cameras, in fact immediate technical expertise when you’ve just started getting serious about photography---would be strangely atypical – after all how can one skip the learning curve?
4. Thank you for the corrections you've made to your review. I have reread the modified version of your review and re-rated accordingly.
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Aug 03 '04
12:25 am PDT
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Re: Re: Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by dkozin, in Electronics
The article at http://www.megapixel.net/cgi-bin/fs_loader.pl?p=http%3A//www.megapixel.net/html/articles/article-dof.html
proves my point (or explains it better). The authours of the article, quote "...seek to explain the observable difference between the depth of field of a digital camera that uses a small-size CCD, and others that use larger imagers or film."
The sample photos show that a DOF for a camera with smaller, 1/2-inch CCD produce greater DOF than a dSLR camera with larger CCD (at the same distance to the subject and the same aperture).
Also, from http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml
"A common complaint about digital cameras is that when using one it's not possible to get nice out-of-focus backgrounds. Why therefore do digital cameras have greater Depth of Field? The reason for this is that the imaging chips on most consumer digitals is very small, around the size of ones smallest finger nail. This means that a normal lens for a format that small is as short as 15mm. A 15mm lens at f/5.6 has Depth Of Field from about 2.5 feet to infinity. Not too much opportunity for selective focus, is there?
This is one of the unspoken drawbacks of low-end digital cameras. Only expensive SLRs like the Nikon D1x, Canon 1D and their ilk have chips close to the size of a 35mm frame, and therefore offer enough DOF to allow creative control over out-of-focus backgrounds."
and finally, from http://www.wmin.ac.uk/ITRG/IS/DPI/HIW/5Camera%20Formats%20notes.pdf
"...Smaller format cameras give greater depth of field than larger formats..."
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Jul 30 '04
10:16 am PDT
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Re: Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by Howard_Creech, in Electronics
1. What you are purporting is a property of the CCD is actually (as I have explained previously) a property of the lens/aperture.
You said---“The camera uses an APS-sized CCD, which is larger than consumer digital cameras and lets you control depth of field much better than the aforementioned digital cameras with small CCDs."
2. Taken out of context the quotes you referenced in your comments and e-mails to me appear to support your position; however a careful reading of the complete article does not support your claim.
Not to beat a dead horse, but rather to sound an alarm for you – no where in all the technical information and facts contained in the article you referenced does it say or allege that depth of field is a property of the size of the CCD rather than the focal length of the lens
3. Remember, you asked for my assistance - there is a problem with your interpretation of the examples you referenced in your comments and with your interpretation of the examples you sent to me by e-mail. Reread what I have written and reread your examples, if you still do not see what the problems are send me an e-mail and I will try to clarify it for you.
I don’t want to take away from the efforts you have made to reword your review and clarify your thoughts, but the problem is not with how you expressed yourself, but rather with the accuracy of what you wrote.
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Jul 29 '04
10:36 pm PDT
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Example (Reply to this comment)
by dkozin, in Electronics
The DOF for same angle of view (27mm 35mm-equivalent focal length), F/2, subject distance 3m
35mm film camera: 2.4-3.97 m (http://www.shuttercity.com/DOF.cfm)
Olympus Camedia C5060: 1.4m-infinity (http://www.wrotniak.net/photo/dof/c5060.html)
The difference is caused by different focal length (even though the equivalent focal length is the same).
You can find more at http://www.wrotniak.net/photo/dof/e10.html
Tables there show the difference in DOF between Olympus E-10/E-20 and 35mm camera at the same equivalent focal length.
The formula for calculating the near and far distance values of depth of field does not depend on the equivalent focal length (which is a virtual value), but depends on the "real" focal length:
"The near and far distance values of depth of field can be calculated as
d = s/[1 ± ac(s-f)/f²]
with plus in the denominator used for the near, and minus — for the far value. The notation is:
s — the subject distance (measured from the lens entrance pupil, see below)
f — lens focal length
a — aperture (or F-stop), like e.g., 2.8
c — the diameter of the acceptable circle of confusion
...
Copyright © 2000-2003 by J. Andrzej Wrotniak.
Reprints and links permitted with proper credits.
this is from http://www.wrotniak.net/photo/dof/
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Jul 29 '04
1:44 pm PDT
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Re: Re: Re: Your review contains some serious factual errors (Reply to this comment)
by dkozin, in Electronics
The same focal distance produces the same depth of field with the same aperture (regardless of the CCD size), I agree.
However, to achieve the same image angle (35mm-equivalent focal length), the digicams with smaller CCD have to use the shorter "real" focal length, which increases the DOF.
E.g. to achieve the same 35mm-equivalent focal lenght of 28mm, the digical with smaller CCD would use a lens with "real" focal length of 18mm (for instance), which would (at the same distance from the subject and the same aperture) produce greater DOF.
I searched the web for comparisons and found this, among other things (http://www.wrotniak.net/photo/dof/):
"I expected the depth of field in digital cameras to be significantly greater than that in 35 mm models. Everybody and his mother knows that. What I didn't expect, is how large the difference is..."
"The bad news is that it is much more difficult, using a digital camera, to blow the background out of focus, which is a pleasing effect in portrait and nature photography..."
Copyright © 2000-2003 by J. Andrzej Wrotniak.
Reprints and links permitted with proper credits.
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Jul 29 '04
11:15 am PDT
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Re: Re: Your review contains some serious factual errors (Reply to this comment)
by Howard_Creech, in Electronics
My concerns with your review relate to what I see as a basic misunderstanding of the mechanics of photography.
Like I said yesterday, depth of field (how far the plane of focus extends in front of and behind the point of focus) is a property of the focal length of the lens and the aperture setting and has absolutely nothing to do with the size of the CCD (or CMOS) sensor. The shorter the focal length of the lens the wider the plane of focus, everything else being relative, will be. --- What this means is that wide-angle lenses have much greater depth of field than normal or telephoto lenses.
Here’s where I think the confusion lies---Non SLR digital cameras (typically) have a small CCD sensor and the zoom lens is precisely matched to the digital format---Digital SLR’s (with the exception of the Olympus E1) utilize lenses that are designed for the 35mm format, which means that the lens IS NOT matched to CCD/CMOS sensor. This results in a magnification factor of 1.4X to 1.6X since the 35mm format is 1x1.5 inches (and the sensors in dSLRs DO NOT measure 1x1.5 inches).
This means that standard digicam lenses should be approximately five times sharper than an equivalent 35mm lens (since the sensor is only about 1/5th the size of the 35mm format) to render the subject with the same degree of sharpness. Obviously, this isn’t the case (digicam lenses are sharper, proportionally sharper than similar 35mm lenses, but not five times sharper) so they do render a sharper image with greater apparent depth of field (this is based on improved detail rendition)—which is great if you are shooting the grand vista (large scale landscapes). This increased apparent sharpness extends throughout the zoom range and when coupled with the combined lens iris/shutter found in most standard digicams makes shallow depth of field (only the subject is in sharp focus) much harder to achieve.
What I think you are attributing to the larger CCD sensor is actually due to the fact that 35mm lenses (with true diaphragms) are able to do a much better job (than standard digicams) of showing shallow depth of field. If your contention (that larger CCD/CMOS sensors “lets you control depth of field much better than the aforementioned digital cameras with small CCDs”) were scientifically correct -- dSLRs (with larger sensors) would also render much better apparent sharpness in smaller aperture shots, much shallower depth of field in large aperture shots, and would provide a wider band of sharp focus in telephoto shots – which they definitely DO NOT.
It may also be that you are confusing depth of field with the magnification factor–Here’s how that works:
If you shoot a specific shot (say a head and shoulders portrait) with a dSLR (and a 35mm format zoom) the image would appear to have 1.5 times less depth of field as an image shot with the same lens mounted on a 35mm camera---due to the fact that depth of field decreases exponentially as magnification increases---however the equivalent field of view would be enlarged by the same ratio (1.5) -- in other words the 35mm image would show one and a half (to one and two thirds) times as much area as the dSLR image. If both lenses were set to an identical (corrected) focal length (say 100mm) the dSLR’s lens setting would actually be about 65mm (instead of 160mm) and the depth of field (and field of view) for both images would be exactly the same.
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Jul 29 '04
10:19 am PDT
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Re: Your review contains some serious factual errors (Reply to this comment)
by dkozin, in Electronics
1. I guess I did not express my thought clearly enough. What I meant is that using the same lens, the smaller CCD will produce the larger 35mm-equivalent focal length than when using the larger CCD.
If using the same 35mm-equivalent focal length (same magnification factor), the larger CCD will actually use the greater "real" focal length, resulting in shallower depth of field.
In other words, the same lens used with a smaller CCD would produce the deeper depth of field at the same magnification (when the same object at the same distance looks the same size as with larger CCD-equipped camera).
Isn't one of the advantages of the larger CCD (and 35mm film cameras) a shallower depth of field at the same 35mm-equivalent focal distance and aperture?
2. What I meant here is that focusing manually, the outer barrel does not rotate and because of it, you can use a linear polarizer without it rotating as you focus.
But you are right about autofocus and exposure readings, I added a note about that to my review. Thanks!
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Jul 28 '04
10:44 am PDT
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Your review contains some serious factual errors (Reply to this comment)
by Howard_Creech, in Electronics
1. You said, “The camera uses an APS-sized CCD, which is larger than consumer digital cameras and lets you control depth of field much better than the aforementioned digital cameras with small CCDs. The CCD has resolution of 6.1 megapixels and the camera can save pictures in JPEG, TIFF or RAW format.” – in addition, you mentioned, “I was using the Pentax FA J 18-35 f/4-5.6 lens”
Depth of field (how far the plane of focus extends in front of and behind the point of focus) is a property of the focal length of the lens and has absolutely nothing to do with the size of the CCD (or CMOS) sensor. The shorter the focal length of the lens the wider the plane of focus (wide angle lenses have much greater depth of field than normal or telephoto lenses). Clearly you were impressed with the very wide plane of focus available with the Pentax FA J 18-35 f/4-5.6 lens, an ultra wide-angle to moderate wide-angle zoom.
The primary benefit of a larger CCD (or CMOS) sensors is a reduction of the magnification factor (with SLR lenses designed for the 35mm format) and a much lower level of image noise -- larger (less complex) sensors (with larger less crowded pixels) produce exponentially less image noise than smaller (more complex) sensors with smaller more tightly packed pixels.
2. You said, “The outer barrel of the lens dow not rotate when focusing, unlike some others. This means you can use linear polarizer instead of having to get a more expensive circular polarizer.”
What you are describing is called an internal focus (or IF) lens -- With modern AF digital/film cameras light entering the lens is divided by a beam splitter and part of the light is directed to the AF sensor and part is directed to the camera’s light meter. Using a linear polarizer (instead of a circular polarizer) blocks/interferes with the ability of the auto focus and light metering systems to do their jobs. Use of linear polarizers (rather than circular polarizers) with modern AF cameras results in inaccurate focus (or the AF system may not be able to focus) and equally important -- light measurement readings will be inaccurate and consequently all exposures shot in auto, program, shutter priority, and aperture priority modes will be incorrect.
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Jul 28 '04
6:36 am PDT
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