If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
Or you can just turn up the in-camera sharpening...
....Did you ever bother to look at the custom functions, Doug? -- http://www.pbase.com/bcbaird |
#22
|
|||
|
|||
Stacey wrote:
Brian Baird wrote: In article , says... Those who don't get the faults, don't push their cameras. Translation: Measurebators will always find faults with their cameras. Actually you're the one who said you can't even manually focus your camera so how would you know? Poor Brian. He's not actually very bright. ;-) |
#23
|
|||
|
|||
Randall Ainsworth wrote:
In article , pixby wrote: Since buying Canon gear I've seen many photographers with 20D problems and experienced some severe problems with my own gear which should not have happened. People seem to think quality is related to price. Canon have disproved that with their 20D. Those who don't get the faults, don't push their cameras. There are too many people with money who buy cameras like the 20D and have no knowledge of photography. 'Twas ever thus. A great many people bought high end 35mm SLRs like the Canon EOS 1N/V and the Nikon F5, only to use them with lousy 28-200mm lenses for taking family snapshots. It's like people who buy a Porsche and use it only for shopping trips. It's called "freedom". ;-) |
#24
|
|||
|
|||
David Littlewood wrote: In article , Colin D writes The lens stops down to f/22 at 18mm, and f/38 at the 55mm end - where you had the lens set - and at that aperture the image will be badly affected by diffraction, so it will not be anywhere near as sharp as at f/11 or f/8. Basically, that sort of aperture is unusable for normal photography. True-ish; f/38 will be very much below optimum for anything other than a pinhole or bottle end. However, it may well be obligatory to get the depth of field required in high ratio macro work (don't forget that that diffraction is determined by effective aperture (which is measured aperture x (1+m)). Also, in large format work, f/45 is quite routine. Yes, it is sub-optimum, but at least you have a lot of resolution to spare. snip True also, but the lens the OP is talking about is a zoom 'macro', not capable of high-ratio work, and of course f/45 in a 150mm lens is entirely different from f/45 in a 50mm lens, for two reasons; one, that diffraction is a function of the actual diameter of the aperture, and a longer lens has a larger aperture for the same f-number than a short lens; and two, there is less magnification of the image required from the larger negative. regards, Colin D. |
#25
|
|||
|
|||
In article , Slack
writes David Littlewood wrote: Unfortunately, current AF bodies (except top-of-range models like Canon's 1-series) are stuck with screen almost totally unhelpful for manual focussing. This is, BTW, a major problem with using DSLRs for photomicrography, one of my main interests. David That should've read, come stock with an AF screen http://www.keoptics.com/Canon20D.htm Although, it will add some $$ to the orig purchase price, at least there is an option available. Thanks for this. Unfortunately, split prisms and micro-fresnel screens are not much improvement for what I want to do. The only satisfactory screen is the clear spot/cross hair type, which gives precise focussing in extreme macro and photomicrography. The "I" screen in the 1-series film cameras is the one I use in those. If it doesn't have a changeable screen, bugger. David -- David Littlewood |
#26
|
|||
|
|||
In article , Colin D
writes David Littlewood wrote: In article , Colin D writes The lens stops down to f/22 at 18mm, and f/38 at the 55mm end - where you had the lens set - and at that aperture the image will be badly affected by diffraction, so it will not be anywhere near as sharp as at f/11 or f/8. Basically, that sort of aperture is unusable for normal photography. True-ish; f/38 will be very much below optimum for anything other than a pinhole or bottle end. However, it may well be obligatory to get the depth of field required in high ratio macro work (don't forget that that diffraction is determined by effective aperture (which is measured aperture x (1+m)). Also, in large format work, f/45 is quite routine. Yes, it is sub-optimum, but at least you have a lot of resolution to spare. snip True also, but the lens the OP is talking about is a zoom 'macro', not capable of high-ratio work, True and of course f/45 in a 150mm lens is entirely different from f/45 in a 50mm lens, for two reasons; one, that diffraction is a function of the actual diameter of the aperture, and a longer lens has a larger aperture for the same f-number than a short lens; Not true. I used to think this until I actually went and studied the physics behind it, but diffraction is purely a function of f-number, not absolute diameter. and two, there is less magnification of the image required from the larger negative. True, which is why I said "but at least [with LF] you have a lot of resolution to spare". This is probably why you think (and I used to think) resolution depends on diameter: the lower magnification factor for a large film means that a higher f-number will be satisfactory. Rules of thumb exist, along the lines of "anything above 4mm (i.e. f/38 on a 150mm lens) is fine". They don't entirely cover the position though. -- David Littlewood |
#27
|
|||
|
|||
|
#28
|
|||
|
|||
"David Littlewood" wrote in message ... In article , Brian Baird writes snip Unfortunately, current AF bodies (except top-of-range models like Canon's 1-series) are stuck with screen almost totally unhelpful for manual focussing. This is, BTW, a major problem with using DSLRs for photomicrography, one of my main interests. It (interchangeable screens) is also one of the more exciting (to me) features of the EOS 5D, if the leaks prove accurate (and if one of the screens is a useful one with clear spot and cross-hair). If you still have problems, send the camera with your lenses to a Canon repair facility. People have reported success after the techs re- calibrated their body and lenses. David -- David Littlewood Boy do you have that right. The screen in my Digital Rebel sucks for photomicrography. I can still use it but its not a pleasant experience. I miss the screens I used in my F1's. But on the other hand the sensor crop means my bellows mount macro lens give me a higher magnification. -- John Passaneau State College Pa. |
#29
|
|||
|
|||
"Cockpit Colin" wrote in message ... Thanks all, My suspicions were aroused when I took a photo of a stream and surrounding vegetation whilst on a walking track (hand held) - it just looked plain blury. I went back later on that day and set the camera up on a tripod. On my 20D with kit lens (zoomed all the way out) At 100 ISO and F29? (or there abouts - stopped down as far as it would go) I ended up with a exposure of 2.5 sec (not a breath of wind, so not worried about anything moving in the breeze). Back on the PC EVERYTHING just didn't appear to be as sharp as I would have expected (shot in RAW too). The whole thing just appeared hard on the eyes - it wasn't until I ran an unsharp mask at 200% over it that it started to look "normal". Not sure if this is the camera, or if I'm expecting too much. I did take some photos of some graph paper later on that night, and it "sort of" appeared OK (difficult to tell). I could send it in for checking, but it probably means doing without it for a couple of weeks Cheers, CC "Cockpit Colin" wrote in message ... Hi all, I have a nagging suspicion that the focus on my new 20D isn't all that it should be. Do any of you have any suggestions on the best way to test this? I was thinking of photographing a sheet of A4 "Math - graph" type paper. If the camera's focus is out, will it be out consistently when focusing on close and distant objects? Should I have the lens wide open or stopped down for the test. Is it possible for an image to be in focus through the viewfinder, and yet be out of focus at the CMOS sensor? Any other thoughts (I only have the one kit lens at this time, so I can't do any lens comparisons). Thanks for your input. Cheers, CC At F29 or so almost any lens will be un-sharp. This is due to diffraction from the small aperture. It is not a lens defect, it is a law of physics. At F29 or so the depth of field really means "every thing is fuzzy". The best aperture to check for focus errors would be wide open or if the lens not of the highest quality, at 1 or 2 stops down from the maximum aperture. Also with a zoom lens use the longest focal length available. If your basing the possible focus problem on a shot at the smallest possible aperture of your lens, I would expect it to be fuzzy. -- John Passaneau State College Pa. |
#30
|
|||
|
|||
"John Passaneau" wrote in message ... At F29 or so almost any lens will be un-sharp. This is due to diffraction from the small aperture. It is not a lens defect, it is a law of physics. At F29 or so the depth of field really means "every thing is fuzzy". The best aperture to check for focus errors would be wide open or if the lens not of the highest quality, at 1 or 2 stops down from the maximum aperture. Also with a zoom lens use the longest focal length available. If your basing the possible focus problem on a shot at the smallest possible aperture of your lens, I would expect it to be fuzzy. Thanks for that. Unfortunately the "nature scene" wasn't intended as a focus test - it was one nice scene that I wanted as a "keeper". I wanted the best possible DOF so I went for smallest aperture - lowest ISO - shot in RAW - put the camera on a tripod - and set the camera for a delayed shot. I knew that a large aperture means poor DOF - I didn't know that small aperture has issues as well (something else to add to my bucket of wisdom!). So far, using an unsharp mask @ 300% @ 0.3 as suggested by Colin D seems to be producing a good result (I didn't know you could select anything under 1 pixel). I'll have to do some more tests to see it F8 to F11 are any better for me. Cheers, |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
advice on battery chargers for Canon | bill a | Digital Photography | 0 | January 30th 05 06:28 PM |
Canon G2: working around crummy autofocus | John Faughnan | Digital Photography | 10 | November 26th 04 09:37 AM |
CANON - The Great Innovator (was: CANON – The Great Pretender) | Steven M. Scharf | Digital Photography | 104 | September 3rd 04 01:01 PM |
Canon digicam advice please | joe at salerno dot com | Digital Photo Equipment For Sale | 2 | September 3rd 04 03:01 AM |
Need advice to choose Canon Elan 7N, 7NE or Nikon N80 | JZ | 35mm Photo Equipment | 8 | August 8th 04 07:49 AM |