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Author Topic: The "Clarity of Resolution"  (Read 9547 times)
BruceK
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« on: April 12, 2004, 10:19:45 AM »
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Dear Digitally_Inclined:

(I wish people would at least give their first names when leaving a message. Replying to a handle is so impersonal...)

You could try an add-on telephoto converter for your existing Sony camera to increase the focal length of the lens. I have a friend with a 717 that's done that and has been happy with the results. You can find decent ones in the 1.4X to 2.0X range that will screw onto the front of your camera. The only other option would be to get another digicam that has a greater zoom range built-in and then use a converter with that as well.

Antoher possibility, which I have not tried, would be to get a small spotting telescope and try attaching your Sony to that. The same effect as the teleconverter, but with far greater power.

I hope this helps.

Bruce
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BJL
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« Reply #1 on: April 12, 2004, 10:57:42 AM »
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I understand if you do not want to wade through the numerous discussion of DOF at this site, even if I enjoy them. I can suggest three ways to increase your magnification while maintaining depth of field; two are fairly obvious
a) as mentioned, a telecoverter
 a digicam of greater "35mm equivalent" focal length, like the Nikon 8700
c) a DSLR sufficiently good high ISO performance and equipped with sufficiently long focal length lenses (perhaps with a teleconverter again).
   It is often the case that, due to larger pixel size, the ISO speed limit of a DSLR is faster than that of a digicam like the Sony about in proportion to the increase in pixel and sensor area. When true, using those higher speed settings is enough to allow using aperture ratios with the DSLR that are smaller by enough to get about the same DOF for the same composition and shutter speed as with a compact digicam like your Sony.

(For example, with many DSLRs ISO 800 to 1600 is as good as about ISO 100 to 400 in compact digicams.)
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Howard Smirh
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« Reply #2 on: April 12, 2004, 11:58:55 AM »
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What I like to see is everything in focus.

May not happen.

If you want to take picture of my stamp collection for example, maybe a flat bed scanner is your best bet.  Unless you want to include the album.  Unless you want to include your den.

Understand what you want first, then the choice of what you want to capture that.  Don't depend on what others want or assume you want.
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Howard Smith
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« Reply #3 on: April 12, 2004, 04:01:27 PM »
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If you want "long depth of field," look at how depth of field is determined and work fro there to make depth of field as long as you want with what you can work with.

Depth of field is a function of the hyperfoacl distance, the and the focus distance.  The hyper focal ditance is a function of the focal lenth squared, the f/stop and the desired diamter f the circle of confusion.

Stop down.  The farther the better as far as depth of field is concerned.  f/16 will give more depth of field than f/2.8, all else being equal.

Don't waste depth of field when focusing at infinity.  Use the hyper focal distance instead of infinity.  There is nothing gained by making the far limit of depth of field farthert away than infinity.  That will make nearer parts of the subject appear to be in focus.  

Don't make big enlargements.

Don't stand too close to the print (increase viewing distance).
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BJL
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« Reply #4 on: April 13, 2004, 09:40:21 AM »
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Depth of field is a function of the ... and the desired diameter of the circle of confusion.
And the circle of confusion diameter is not an arbitrary choice: to get the sharpest possible image of an object, as you seem to want, the object should be within the DOF range computed by using a CoC value comparable to the size of the smallest feature that the camera (sensor and lens) can resolve. This means that you probably want it very roughly the same as the pixel size; maybe more like twice the pixel size in practice.

To get beyond this hand-waving vagueness, experiment, or find an experiment that someone else has posted on the web! Norm Koren's site http://www.normankoren.com/ is often great for this sort of technical and experimantal stuff.

An easy, crude initial experiment is to make a sequence of photographs of a scene in highest quality JPEG mode, gradually opening up the aperture, and look at the file sizes. As OOF blurring increases, the file sizes get dramatically smaller, since the JPEG compression is smart enough to realise that there is far less detail in many parts of the image, and so compresses those parts a lot more. Check against how the image looks, and see how file size is related to perceived sharpness.

Indeed, some digital cameras have a "best shot" mode that chooses the sharpest of a sequence of shots on the basis of having the biggest JPEG file size.


A cautionary example of what would be a very poor choice of circle of confusion value for your purposes, even though some sources might seem to suggest it:

If you were to use a traditional DOF scale for 35mm format, which assumes a 35 micron CoC, with a camera like you F717 whose sensor has 3.4 micron pixels and which can resolve details as small as about 5 microns or less, that DOF scale would be counting some objects as being "in focus" even though they are blurred down to about one tenth the sharpness of objects at the focal plane; the image of each point at the supposed limits of DOF would be smeared into a circle of confusion covering about 100 pixels!


If instead you count something as being in focus only when it looks about as sharp as the sharpest part of the image, an appropriate value for the circle of confusion should be very roughly the same as the resolution scale of the camera, which with a good camera (including a good lens) is usually about 1.5 times the pixel spacing, because of the way that Bayer interpolation works. Teleconverters can noticably reduce sharpness though, as you seem to have observed.


P. S. Some things you can read in forums and even in photography books are written in the traditional context of film photography, and sometimes even specifically for 35mm format film and lenses. For example, they might assume the resolution capabilities and enlargment factors typical with such equipment. Even worse, they sometimes assume the more severe resolution and enlargment limitations of the films and lenses that existed half a century ago, when the DOF scales for 35mm lenses were standardized.

Some people make the mistake of taking these statements out of context, believing them to be universal truths, applicable even to cameras and lenses of far greater resolution and far smaller formats that are typically used with far greater enlargement factors.
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Howard Smith
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« Reply #5 on: April 13, 2004, 03:57:34 PM »
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Justin, there isn't a real simple answer.  To make things as simple as I can;

- stop down as far as you can.  The trade is long shutter speed with attendent motion problems (camera jiggle, air currents, suject motion, etc.) and diffraction from small aperature.

- don't waste depth of field by focusing at or near infinity.  The depth of field behind the subject will be wasted if it falls farther than infinity (calculated distance).

- try to compose to reduce or eliminate foregrounf objects that are "close" to the camera, nearer than the fodward limit of depth of field.  Try to compose "two dimensional" subjects.

- make small prints to keep the circle of confusion smaller on the print.

- use a long viewing distance.  The farther away you stand, the fewer problems you will see on the print.  You can tolerate a larger circle ofconfusion on the print without seeing it.

- use the out of focus elements to seperate the focused subject from its environment.  Make the out of focus parts work for you instead of against.

- experiement to find what rally works for you.
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Digitally_Inclined
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« Reply #6 on: April 14, 2004, 12:11:09 AM »
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Well, Justin, it seems clear what you should be looking for. Any one of the new breed of 8 megapixel fixed lens cameras would be your best option. The Nikon 8700 has a longer reach (280mm) and might be preferred for that reason. However, the Minolta A2 has an image stabiliser which will greatly facilitate the taking of sharp images at 200mm, and of course has a wider angle at the other end.

The Minolta A2 would be my recommended choice, if I've understood your circumstances.  
All of the photo's I have seen (on Pbase), with the new 8mp cameras, seem to be rather less than what you get out of a good 5mp. I would think that it's due to the downsizing of the pixels, which can be a bad thing, if I'm understanding some of what I've been reading. The larger the sensor, the better (to a point) and that's part of why the new 8mp cameras do not seem to have the clarity, due to the smaller pixel size. (gathered from Norman's site). The thing that strikes me as odd, is by the "numbers" the Sony F717 should be one of the poorest cameras out of the bunch, when looking at what it would be compared to film, as far as clarity when enlarged, but I have found it to be excellent and it gives me tack sharp pictures, that need hardly any post processing.... The 18x24's I have are from that F717 and from 2-3 feet, they rival any blow up from film that I have...  But the numbers on Norman Koren's site, say the opposite should be true...  When things go aginst what the numbers and science say, it get's confusing to understand...

I have looked at all four of the 8mp cameras, but since they all use the same sensor, I see only little difference in colour values. Purple fringing and grainyness seem to be in photos from all four.  The Canon seems to be the best overall, followed by the Minolta, then Sony and Nikon last. (my personal opinion). Of course taking them down to an 8x10 size helps dramatically, but I'm talking not taking them down, but being able to print them at size instead of downsizing.  An easy way for me, is to open a photo up in Paint Shop Pro (can't afford photoshop right now), and resize it 150%. If it's grainy as heck, I don't consider it good, but with the F717, when resized to 150%, the photo's are still very good and markedly smoother than any other camera I ve tried...  I do not know why, I just know what I see and that's the kind of thing I want from a camera with a bigger lens...
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Howard Smith
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« Reply #7 on: April 14, 2004, 08:23:08 AM »
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Justin, the addition of an auxiliary lens may cause a slight focus shift when focused wide open and then stopped down to make the image.  Perhaps that could be the cause of "softening."

Expecting DoF like you see it with the human eye may not be realistic for a camera.  When you focus on a subject, objects closer and farther away may actually be outof focus, by your brain fills in some detail and tends to overlook the fuzzy details.  When you check around, your eye will autofocus.  This an give the impression of very great DoF for the human eye.  The camera just records what's there.

An 18x24 prnt from an F717 is a huge enlargement.  A very small CoC on the sensor will be very large on the print.  Two to 3 feet is pretty close actually for viewing an 18x24 print.  There are exceptions of course, like large format books.  Maybe you are just expecting too much from the equipment you have.

And don't forget that the DoF of a print will be different for different people.  If you have the eyes of an eagle, your DoF will be less than for me, even with my bifocals.
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Digitally_Inclined
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« Reply #8 on: April 14, 2004, 10:01:52 AM »
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An 18x24 print from your F717 is more like a 20X enlargement.  That will require a CoC on the sensor 1/4 the size to get the same 1/100 CoC on the print.  This doesn't take into account changes in viewing distance ssumed for a 5x7 and an 18x24.
Here's some links to photo's that may show better what I'm talking about. I uploaded a few.  The first is a Train that sits as a museum piece. The next two are shots of trees. The next is just a close up, but I couldn't resist including it. I just love the pic.  The last is a 100% crop of the photo taken to 18x24.  

Train

Leaves1

Leaves2

Flower

100% crop


Let me say that what I did to get the 18x24 was to take the photo, add sharpening in PSP and send the file off to the print place I use on the web. They returned an 18x24 glossy on Kodak photo paper, to me...


Even in these photos, "everything" is not in focus, but a large part is and that's what I am looking for in a camera with longer telephoto. These were all taken without doing anything more than turning on the camera and taking the picture. No manual settings of Aperature or shutter speed. Just Auto mode...  Every other camera I've tried so far gives a very shallow DOF in Auto mode, about half as much as you see in these photo's. That's why I haven't found anything better than the Sony so far...  (at least that I can afford). I can reproduce this in 35mm and I imagine on a 10D as well, with an expensive lens...  Don't get me wrong, if the Canon lenses weren't $3,000-$8,000 a piece, I would be shooting Canon, but at 2-3 hours every 2-3 weeks, that's just not worth it...
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BJL
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« Reply #9 on: April 14, 2004, 10:14:18 AM »
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Justin,

    sorry for my bad habit of giving detailed explanations for optical facts, instead of just stating the practical consequences. As Howard Smith has said, getting large prints in which subjects over a range of distances look sharp from a small sensor camera like the F707 requires keeping the circles of confusion far smaller than the value used on a traditional 35mm lens DOF scale, due to the far greater enlargement factors involved. So numerical DOF examples published in many photographic books can be misleading. Online DOF calclators like
http://dfleming.ameranet.com/dofjs.html can be more useful, if used with care.

It seems that you are for now constrained to a high end digicam (probably 2/3" format like the F707), so the most practical issues seem to be

a) Beware comparing images from different cameras of different pixel counts at 100% on screen: comparing at the same image size (like "fit to screen") is far more relevant to how sharp your prints of a given size will look. Another somewhat fair way to do it is to downsample files from 8MP cameras to 5MP and compare those versions to files from 5MP cameras.
   When compared this way, I see some of the new 8MP cameras giving somewhat sharper images. Sony 828 images downsampled to 5MP are still sharper (but slightly noisier) than 5MP images from the 717, if examined very closely. Check out the Sony 828 review at DPReview.

 For optimal sharpness, getting the longest possible focal lengths from the camera's built-in lens is usually better than using a telephoto supplementary lens, as supp's usually degrade sharpness. Hence the Nikon 8700 idea.

c) In the realm of tele supp. lenses, the Olympus E-20 with its big 3x supp. (giving a 35mm equivalent FOV of about 420mm) is apparently of very good quality, but is also very big and rather expensive compared to most digicam options. At that stage, you might be better off with an entry level DSLR and a cheap, long lens like some of the Sigma ones.
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George Barr
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« Reply #10 on: April 16, 2004, 08:29:33 PM »
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oops - that's 380 mm. not 280 and 3800.
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Digitally_Inclined
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« Reply #11 on: April 12, 2004, 12:42:58 AM »
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Hello all,
I'm new to these forums and hope that what I speak of and ask, will not be too redundant, nor too naive.

I have worked with digital cameras since they first came out, just as total amateur. I am not really very knowledgeable about the Technology, but I know a little, just enough to get me into trouble as usual...

My questions pertain to figuring out how to judge which digicam or DSLR will be the best for what I want to do, or if it does not exist within my limited budget...

My love of the outdoors and wildlife, leads me to desire to take photos of those things. My quest is to find a way to take photos which are pleasing to my eyes, no one else's, just to me...  I don't intend to ever sell or "share" the images I take, except maybe with a few friends...

The problem I have, is that I absolutely do not like photos with a short DOF. I do not like portrait style. I like a photo to show what I see, which is everything in focus. I also want to be able to do (or have done) prints up to 24" or better, from digital photos that I have taken.

That said, I have used many digital cameras over the years, from cheapies, to DSLR's and so far, the only one that I have enjoyed using due to it's ease of use and natural tendency to give me the type of photo I want, is the Sony F707/717.

I should say that I only get maybe 1-2 hours every couple of weeks, to take photos, so time is precious and I don't need to have to use a camera which requires constant manual adjustment. I also have a need to have a camera which has a longer telephoto reach than the F707/717 does...  I have tried DSLR's including a 10D, but the reality of those, is that I cannot and would not ever have the funds to buy the "L" series lenses, to be able to get the clarity I'm looking for... That's why I didn't stick with DLSR. A DSLR with a cheapo lens, is totally worthless… I have learned that the hard way.

For whatever reason, the F707/717 seemed to give me the closest to what I wanted in DOF, without having to do a lot of manual adjustment to get it and it has made the "clearest prints" that I've ever gotten with any camera. I have an 18x24 hanging on my wall that is simply beautiful, not grainy or noisy.  What I don't get is the telephoto distance that I need.

So the question is, are there any cameras out there that would get me closer to my subjects than the Sony, but give me the same "clarity" that I see with the Sony? Also, what is the key in the F707/717 that makes it do so well, when even by what is written on this site, it shouldn't lend itself to large prints at all...  How do you tell which camera will be the best, when some that should be good seem to be bad and some that shouldn't be good, are good? ...

I realize that what I see as clarity is DOF, I just call it clarity of resolution...  

Thanks in advance for any thoughts you have.
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Lin Evans
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« Reply #12 on: April 12, 2004, 10:36:51 AM »
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Just a couple of thoughts. You could use the F707/F717 with a 1.7x tele converter like the Olympus TCON-17 which would extend the 190mm focal length to 323mm. You could use the DSC-F828 with the same tele converter to get 340mm.

The only problem I see is that neither of these - in fact none of the fixed lens digicams are too great a tool for shooting wildlife since you really need about 600mm focal length and you need much faster autofocus than most fixed lens digicams have.

The 4 megapixel Panasonic FZ10 with the Leica F2.8 lens, 12x optical zoom and optical stabilizer will get you 420mm, but it's not going to be able to print quite as large as the 5 or 8 megapixel versions. (I have all the above mentioned cameras).

I really don't have a good recommendation. Of the approximately 25 digital cameras I use, the only ones which I would recommend for any serious wildlife use are the Canon EOS-1D and EOS-10D. Both are dSLR's and I only recommend the 10D because of the 1.6x crop factor and its effect on telephoto. Depending on your expectations of depth of field, you would probably be better off with a fixed lens digicam like the Sony's, but again getting the needed telephoto is not an easy task.
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Lin
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« Reply #13 on: April 12, 2004, 11:54:54 AM »
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My name is Justin...  I've become used to the anonymity of the internet and the "handles"...  

I have tried several teleconverters on the F717 (B-300, TCON-17, etc). They do work, but I see a loss of "crispness", the photos seem to look more (how do I describe it?), like the pixels have been mushed together, or smoothed out, like an oil painting, loosing definition...  

I think that what I desire is unreachable within my limited budget...  I too feel DSLR is probably the only way, buy only with expensive lenses. I have tried it with several lower priced lenses and again, you loose definition...  Where the expensive well made lenses have it.

I usually look at f8 for aperature or higher. That gives me the "look I want"...

Thanks for your responses. It's much appreciated.  

I have given thought to something like the Nikon 8700 or the DMC-FZ10, but again it will not really get me out there, where I need to be. I figure 600-800mm is about what I need, due to lack of time to devote to sitting or sneaking up on wildlife, to get the closer shots...
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BruceK
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« Reply #14 on: April 12, 2004, 02:44:39 PM »
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Justin:

When you tried the teleconverters with your F717 did you use a steady tripod and either a remote shutter release or the self timer? It could be that the softness you saw was due to camera shake and not the optics.

Bruce
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« Reply #15 on: April 13, 2004, 05:42:48 AM »
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Justin:

When you tried the teleconverters with your F717 did you use a steady tripod and either a remote shutter release or the self timer? It could be that the softness you saw was due to camera shake and not the optics.

Bruce
I used a tripod and self timer. I did some testing with a given subject, without the teleconverters and with the teleconverters and all the results with teleconverters were unacceptable to me... I'm sure that they might be acceptable to some, but the loss of clarity and crispness, wasn't worth the gain in focal length...
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Howard Smith
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« Reply #16 on: April 13, 2004, 07:15:20 AM »
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I have an F707.  The digital zoom is prety bad.  Do you have it turned off?
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Digitally_Inclined
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« Reply #17 on: April 13, 2004, 10:49:57 AM »
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Howard: I never use the digital zoom feature since it only interoplates the normal image and does not do a good job at all...

BJL: You are way over my head. I caught some of what you said and in visiting sites like Norman's, I catch some of it...  The drift I get is that what I would want in digital is not really here yet, at least not really affordable to grunts like me and maybe that is a good thing.....

What I also see is that digital must be treated totally different than 35mm in many ways and there's a large learning curve there. I continue to read and experiment, but I do not suspect that I wil ever become well versed on most of this....

I've thought for a long time of starting a review site, for digital dummies. It would cover about 90% of us out here. A review site where the approach is "I just want a good picture out of the box" and review cameras from the standpoint of what do I get when I just turn it on and shoot?  I would think it would be an interesting twist, seeing as all of us who do not know, really spend most of the money buying digital and paying for the technological advances... I think there should be a site for all the dummies to go....

But that's another subject.....  Again, thanks for the feedback. You make me think and look for answers, and that's good...
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Ray
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« Reply #18 on: April 13, 2004, 07:53:18 PM »
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 I have tried DSLR's including a 10D, but the reality of those, is that I cannot and would not ever have the funds to buy the "L" series lenses, to be able to get the clarity I'm looking for... That's why I didn't stick with DLSR. A DSLR with a cheapo lens, is totally worthless… I have learned that the hard way.
Well, Justin, it seems clear what you should be looking for. Any one of the new breed of 8 megapixel fixed lens cameras would be your best option. The Nikon 8700 has a longer reach (280mm) and might be preferred for that reason. However, the Minolta A2 has an image stabiliser which will greatly facilitate the taking of sharp images at 200mm, and of course has a wider angle at the other end.

The Minolta A2 would be my recommended choice, if I've understood your circumstances.  Smiley
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Digitally_Inclined
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« Reply #19 on: April 14, 2004, 12:32:31 AM »
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As far as DOF goes, let me give a couple of examples. There's the easy one where you shoot a barbed wire fence line and everything's in focus fron the foreground out to a long distance down the fence. Or looking up into a tree and focusing on the leafy brance a few feet above you, but having most or all of the tree in focus as well, so that it looks more as the human eye sees it. I've done those with film many times and I've done those with the F707/F717, but I have yet to duplicate it with any other digital I've tried, at least not to the extent that the F707/F717 does...  Maybe that gives a better understanding of what I mean by DOF. I just don't care for "soft" photos. I do not like portraits or even wildlife shots where only the animal or part of the animal is in focus...  It's just my personal preference. It doesn't mean I think the pictures are bad. It just means I don't care for that style...  I guess I'm too much of a realist...

Actually the F707 was the best at giving this "look" and the F717 does tend to give "softer" photo's. I asked a Sony rep once about it and the answer I got was that the F717 was done that way on purpose because most people do not like everything in focus and it was an issue with the F707...  Now I don't know if he was just pulling my leg or not, but that's what I was told at the time...

Again I thank you all for taking the time to discuss this with me and offering your insight. I see there are many, very well versed pro's around here and I feel a little out of place at times...
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