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Old Nov 4, 2008, 12:13 PM   #31
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Thanks again for your input JohnG. I understand what you're getting at and the automatic car transmission analogy was very helpful.

Maybe I need one more bit of clarification regarding depth of field. You've mentioned that point-and-shoot cameras have a much greater DOF than DSLRs. So can I take that to mean setting the apature on my S2 to f/3.5 is not the same as f/3.5 on my XSi? Would there be some way to figure out equivalents? Something like "you need f/22 on your XSi to = f/8 on your S2?"

I wonder if that's a strange question... I guess I'm trying to understand based on what I already know.

I don'tnecessarily think there's anything wrong with my camera. But I have yet to see any image quality improvement from my XSi over shots I've taken with my S2. (And I have a feeling that my S2 will continue to be my go-to camera for indoor functions, especially ones under low light, as I'm unwilling to carry around tripods and external flashes to produce quality shots.)
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Old Nov 4, 2008, 1:17 PM   #32
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Boldstar wrote:
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Maybe I need one more bit of clarification regarding depth of field. You've mentioned that point-and-shoot cameras have a much greater DOF than DSLRs. So can I take that to mean setting the apature on my S2 to f/3.5 is not the same as f/3.5 on my XSi?
EXACTLY CORRECT!! for DOF purposes they are not the same. For Exposure purposes they should be roughly the same. The primary reason they are not the same is that is only 1 variable in the DOF equation. Of the 4 variables I mentioned, PHYSICAL (not 35mm equivelent but physical) focal length is the major reason why the two are different. As an example at the long end, the S2 is 432mm equivelent but only 72mm PHYSICAL focal length. It's the 72 value that's used in DOF calculations.

On your DSLR, a 270mm lens would give you roughly 430mm EQUIVELENT focal length (so, same field of view as the S2 at full zoom).

Here's a link to a calculator. You can plug in both cameras and see what results you get.

A quick test of XXD vs S2 dof I did was at 100' at f8 (s2 at 72mm = 432mm equiv and xxD at 270mm = 432mm equiv):

S2-IS DOF = 49.7 feet

xxD DOF = 12.6 feet.

That's a pretty big difference.

http://www.dofmaster.com/dofjs.html
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Old Nov 4, 2008, 2:15 PM   #33
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Boldstar wrote:
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I don'tnecessarily think there's anything wrong with my camera. But I have yet to see any image quality improvement from my XSi over shots I've taken with my S2.


(And I have a feeling that my S2 will continue to be my go-to camera for indoor functions, especially ones under low light, as I'm unwilling to carry around tripods and external flashes to produce quality shots.)
It's very common for people moving from a P&S to a DSLR for their photographs to get worse before they get better; the tempation is of course to blame the equipment. But if you stick with it they will get a lot better.

If you climb into a race car and try to go around the track, chances are your laps will be slower at first than with a BMW saloon. But once you adjust to the new equipment you can do much better.

First though you have to be willing to accept that YOU have to learn how to be a better photographer, the more expensive the camera the LESS it will do for you. But the potential gets greater.

Everyone has a convenience v performance limit for different situations. Look at the gear the paparazzi carry around their necks. Big cameras, big lenses, big flashguns. Most people won't do that when they go to a party, because well, they will look like a professional photographer. But if you want the shots you need the gear. The rest of us settle somewhere in the middle, and find a style that suits us. Or just decide not to do certain types of photography.

For example I quite like bird photography, but I have no interest in spending the kind of money I would need to to get the kind of shots I want. So instead I make do with the occasional decent shot when circumstances allow, but mainly I just don't photograph birds.

If you want great indoor shots, then you need the right equipment. But maybe you will just settle for P&S snapshots because the hassle and expense of carrying pro equipment is too much, not to mention the fact that you need to learn how to use it.

Don't forget most pros spend years all day every day learning about photography, that is why they can take the pictures they do.

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Old Nov 4, 2008, 3:00 PM   #34
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I love the analogies!

I'll admit, my reason for investing in a DSLR wasn't a very good one. At the time, I was eager for a new toy. And my S2 had seen a lot of action. I thought using a DSLR would be fun and produce better photographs than I was already getting. I'd more or less mastered the S2 and was looking to step up. But I didn't give a whole lot of thought to my most frequent subject matter. Perhaps a newer S-series camera would have been sufficient.

My #1 motivation behind taking pictures is to preserve memories. I'm building a massive collection of prints in photo albums, very up-to-date, all in chronological order. Most of the timeI'm taking pictures atsocial gatherings(weddings, Christmas parties, cottage gong shows, etc.), or on vacation. And of course, my most frequent subject is our dog. I share these archives (and laughs) with friends from time to time, and I hope it'll someday be an entertaining collection of photos for my kids, grandkids, etc.

All that being said, it's a growing hobby for me and I'm starting to get more into landscape, action and night photography. So I still hope to put lots of mileage on my XSi, but I can forsee lots of opportunity to keep using my S2.

Sorry if I got off topic there...


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Old Nov 4, 2008, 6:07 PM   #35
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JohnG wrote:
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shoot. I should have mentioned that this is not exclusive to the 50mm lens. My tamron 17-70mm focus wanders from front to back and my other canon lenses, 50mm f1.8 and 28-135mm IS are slightly front focused as well. This applies to both cameras. It's consistent and with the changes to my technique, I don't plan on sending anything back to Canon.
Out of curiosity, just wondering if what you see is actual front-focus vs. the fact that an image typically has more in-focus in front of the focal plane than behind.* For instance if you were shooting a ruler (typical focus test) - yes you want to see the point you're focusing at in-focus but you should NOT see an equal amount of distance behind the focal plane and in front of the focal plane in focus.* The fact you're describing the same affect with 4 different lenses across 2 different bodies makes me wonder.* You also mentioned you changed your technique and thus are not going to send in your gear.* Does that mean that your change in technique has resulted in more consistent focus?
I'll post some images of the focus test. The Tamron showed front focus, back focus and mid focus. The canon did not focus in the middle, but usually caught the intended subject in focus along with the front. I was shooting the printout of the focus test chart from http://www.focustestchart.com. That's a nice little page.

The changes in my technique have expanded the DOF so that I'm not shooting at a razor thin focus field. Increase the f-stop, ISO, and use the flash more. I got some good rechargeable batteries and a lightsphere for it.
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Old Nov 5, 2008, 9:25 PM   #36
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First I want to lend my total support to Boldstar for his post on Tuesday. I agree 100% with his statement that the first requirement of a Camera and/or lense is it must focus correctly. None of us would be having these "Discussions" if the camera was working as it should.

John G,...Boldstar asked a series of questions about FOCUS and your gave him an answer about DOF,.. which was absolutely correct, but my response was "It didn't answer his question about focus". Come on,... we all know you guys are the experts, and you know more than we will ever learn,... but we are not exactly dummies.

I expect a new XSi to shoot 20% better resolution pictures than a G7 with a 10mp res. But first off it has to be correct in focus and if is't not, how can you compare. I have already seen that the ISO improvement in the XSi over the G7 is fantastic. The nose reduction is just great. MyXSi shots at ISO 1600 are as good or better than the G7 at ISO 400. But my portrait shots with the G7 are 10x better than anything I've shot so far. The G7 images are sharp and clear at 200x and the XSi are not in focus at 100x.

I totally disagree with anyone that says you have to have a $3000 body and a $1000 lense to take a good picture and expect it to be sharp.
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Old Nov 6, 2008, 5:12 AM   #37
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jbird1938 wrote:
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I totally disagree with anyone that says you have to have a $3000 body and a $1000 lense to take a good picture and expect it to be sharp.
No disagreement here. Anyone telling you that is full of it. BUT it depends on expectations. And, no one is saying people are dummies just that the focus systems on DSLRs are different than digicams and because the DOF is so much thinner, mis-focuses show up much easier on DSLRs. Again, if you're unhappy with the gear send it in to Canon for callibration. That's the recourse. Sure the gear could be faulty. But what you're running into here is that the experience of people here (including our own experience) is that 80% of bad pictures are the result of user error. Then about 19% are just using the WRONG gear (i.e. taking low light shots with kit lens) and about 1% gear failure. You're going in circles now though. Send your gear in for calibration. Not really much point in going back and forth anymore.


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Old Nov 10, 2008, 11:29 PM   #38
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JohnG,... My XSi is off to Canon and they acknowledge they got all 3 pieces, Body and 2 lenses. I should have it back in one week.

I've shot enough pictures with both P&S and DSLR's to see my share of mistakes, but like I've said, I've started shooting 45 years ago with a Pentax SLR and all I had was the Body, the lens, and film. Those original camera only had one button and that was the Trigger.

I know that DOF is a killer for closeup shots but here is my point. I shot the XSI in AE mode, singlespot AF at 55mm and a distance of 2' a f/11. I repeated the same test using my G7 set at AE singlepoint Continuous Focus at 44 mm, distance=2' and f/11. According to the DOF charts the XSI has a DOF of 1.9" and the G7 has a DOF of 1.0". The Center of the DOF for the G7 was dead on. The XSi focus was FF on some shots about 3/4 but the image was still not in focus,.. so it must have been more since the DOF would still have left the image in good focus. In a couple of shots the XSi was Rear focused but no way to tell how much. Image was not in focus.

I really do hope that Canon does find something out of adjustment, otherwise I feel that there new Autofocus system has a short fall and can't lock focus on some low contrast(gut excellent light) images.

In other posts I've seen on this forum another guy has posted some pictures of glass figures of ballet dancers. Clearly there should not be any problem to focus on his target but there was. He has the same shot with a Sony Alpha camera and the focus is great and the entire depth of field is visible on the image.

I printer out my DOF tables using the correct camera and lens from

http://www.dofmaster.com , you just have to select your camera and lens.
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Old Dec 5, 2008, 4:16 PM   #39
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jbird, what was the result of your calibration?
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Old Dec 6, 2008, 8:04 PM   #40
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I've updated my logon to my correct User ID,...Jbird is gone. I got all of my Canon stuff back from them with the only commet was the "Camera was In-Spec". Not another word. Also, both lens were in spec.

I took the camera outside and started a new series of test. I got similar results as before. The AF system will easily lock in on medium to high contrast objects but still will not get the correct lock on a monolithic Magenta or white flower pedal. What it seems to do is lock in at the front edge of the DOF, especially when the DOF is at or about 1". I tested my G7 using the same fstop, 55mm, and distance from the image and the G7 never fails to get the target in focus. I've check the specs on the G7 and the DOF is not any large at all when you match all 4 DOF factors.

So I modified one of the Focus Targets and mounted it on a stick that I could set in the ground right next to the pedal of a flower I was taking. I used single point focus in Av control and used a setup that would force a DOF of 1-1/2". It failed each time to focus on the pedal of the flower and was in great focus at 1-1/4" in front of the flower.

According to Canon, this is in Spec, since there spec is "All the camera and lense have to do is focus within the DOF. The problem with this is not all things in MY DOF seem to be sharp.

I need to change the Focus Target such that it will be more accurate in show the distance in front and to show the full DOF the camera has captured. Using Canon's ZOOM browser you can see all the shooting data and the AF point.

We are a little busy around here with Family and Xmas so I don't know when I will get back to testing. My view on the Canon spec is that I expect the Camera to focus at or +- 2mm from dead center of the DOF. I have 4 other Canon P&S Cameras and all of them can do it. If Canon didin't think their entry level DSLR could or should do that, then why do they have the "Creative Modes" controls similar to every other P&S they make.




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