Search results for 'sensor cleaning' - page 131
My first mount conversion
are there no worries with the exakta mount hitting the mirror? I don't think so, certainly not an a crop sensor DSLR anyway - I checked the Meyer above by measuring how far the rear of the Exakta mount protruded from the flange and it is similar to the protrusion of the rear element of my Chinon 55m...
Posted by sorted78 on 07/04/2011 - 08:53
Prime?
So my 100mm macro stops being a telephoto if I focus close-up? The F 100-300 is only a telephoto when zoom ed to beyond 170mm, whilst several of my 50mm lenses are telephotos at least when focused on infinity... I think you'll find it's one of those words here the definition has changed. In a sim...
Posted by MostlyHarmless on 05/04/2011 - 22:48
Prime?
(And my 100mm macro may not be a telephoto even at infinity since it's always > 100mm - just - from front element to sensor plane:)) I see your adding the rear flange distance now (Your original definition only mentioned the length of the lens) Mine is ~95mm with both caps on. I guess the 500mm ...
Posted by petrochemist on 05/04/2011 - 23:59
Prime?
I see your adding the rear flange distance now (Your original definition only mentioned the length of the lens) Mine is ~95mm with both caps on. I guess the 500mm Newtonian telescope I have is actually only telephoto if used with an eyepiece (and the camera of course) - it must be about 1m long ...
Posted by pentaxian450 on 06/04/2011 - 00:13
Who needs a big white one?
On a crop sensor a 1500mm equivalent lens of little use over and above curiosity value to any but the most specialized of photographers. As someone who hired a Nikkor 2000mm lens to photograph an IRA siege in my Fleet Street days, I can seriously say don't bother. The main use for a lens such as ...
Posted by lemmy on 05/04/2011 - 22:54
Portrait Lens
Hi Guys, In the days of film I used to use a 100mm lens for portraiture I now use a K10D which has a 1:1.5 ration CCD:35mm So is this (100mm) still a good maxim or should I be looking at 70mm? As 100mm equates to 150mm (35mm) would this still be suitable for portraits? - seams a bit long t...
Posted by Frogherder on 06/04/2011 - 10:22
Portrait Lens
This question comes up so often I wrote an article on it:
Posted by rparmar on 07/04/2011 - 13:00
Macro help
I think first, you need to understand what is meant by macro photography. Macro photography requires a lens, or a combination of lens and extension tubes, that is capable of producing images at 1:1 magnification, or greater. That is, if a subject measures 1 centimetre in real life, it's image mea...
Posted by Mannesty on 06/04/2011 - 15:55
Why do some lenses have front/back focus issues?
I've recently bought a Sigma 30mm f/1.4 and in reading up on it beforehand, it appears that these lenses are prone to front/back focus issues. Fortunately mine doesn't seem to be affected, but I'm a bit confused as to why any lens should be. From what I understand about the AF system, it adjust...
Posted by sorted78 on 14/04/2011 - 21:26
Why do some lenses have front/back focus issues?
but if it's out of focus at the Main sensor, then the info at the Focus sensor should also be out and an adjustment made !? as both light sources come through the same lens ?? is this not so ? I'm confused with this too ! links to more info required please :)
Posted by Cisco on 15/04/2011 - 11:24
Why do some lenses have front/back focus issues?
I agree. For normal "closed loop" control, the camera would adjust the lens until it was in focus. Hence the only calibration would be that the focus sensor and the actual photographic sensor were the same distance optically. However, my logic tells me the fact that one has some lenses front foc...
Posted by timd on 15/04/2011 - 12:03
Why do some lenses have front/back focus issues?
I agree. For normal "closed loop" control, the camera would adjust the lens until it was in focus. Hence the only calibration would be that the focus sensor and the actual photographic sensor were the same distance optically. However, my logic tells me the fact that one has some lenses front foc...
Posted by Oggy on 15/04/2011 - 12:23
Why do some lenses have front/back focus issues?
but if it's out of focus at the Main sensor, then the info at the Focus sensor should also be out and an adjustment made The focus sensor is located below the mirror box, and the light is reflected to the focus sensor trough a secondary mirror located behind the main mirror. If any of these compone...
Posted by pentaxian450 on 15/04/2011 - 15:42
Why do some lenses have front/back focus issues?
But ALL those components are in the Camera body !! So how can the lens make any difference ?? It will be the same error for ALL lenses ?? No ? :? Lenses also suffer from manufacturing variations. The focus sensor might not see the light exactly as the image sensor does. Add to that the color f...
Posted by pentaxian450 on 15/04/2011 - 15:52
Why do some lenses have front/back focus issues?
I simply wanted something Objective, rather than your Subjective findings :) My findings were objective not subjective. From your link : It can therefore instruct the lens to move directly to the correct position, without taking a second measurement or "hunting" around. :D You forgot...
Posted by Smeggypants on 15/04/2011 - 20:53
Why do some lenses have front/back focus issues?
It can therefore instruct the lens to move directly to the correct position, without taking a second measurement or "hunting" around. It doesn't exactly works like that. Since some lens have a longer focus throw than others, and since some lens screwdrive don't all use the same "drive ratio", the A...
Posted by pentaxian450 on 16/04/2011 - 00:43
18-135 has been slaughtered by Photozone
Scored one and a half stars (I think) :shock: I wonder if it's anything to do with the K-5 sensor having more pixels, although they tested the 35mm f/2.4 on the K-5 and that was OK :shock:
Posted by Algernon on 16/04/2011 - 20:28
18-135 has been slaughtered by Photozone
Scored one and a half stars (I think) :shock: I wonder if it's anything to do with the K-5 sensor having more pixels, although they tested the 35mm f/2.4 on the K-5 and that was OK :shock: It shouldn't do: if I understand it rightly, having a higher resolution sensor increases the maximum result...
Posted by MrCynical on 16/04/2011 - 21:22
18-135 has been slaughtered by Photozone
It shouldn't do: if I understand it rightly, having a higher resolution sensor increases the maximum result which can be measured but does not decrease anything. For example if they were to retest the FA43 with the K5, then its measured centre resolution at f4 would be higher (because it exceeded th...
Posted by pentaxian450 on 16/04/2011 - 22:41
fish eye
The Samyang 8mm seems well thought of, but if I was after something wider than 18mm I'd probably go for their 14mm instead. It's full frame compatible so would double as a fisheye on film Not really as it's rectilinear, you would end up with an ultra wide angle lens. John Even better then! :lol: ...
Posted by Dangermouse on 23/04/2011 - 15:07
