Search results for 'back focus' - page 748
Sunagor 500mm "telescope"
I have the above lens but have not been able to find anything about it on the web. My question is: - It has a standard manual focus, then moving towards the camera it has variable aperture f8-f22 ring. Next is a ring which has O C. This interacts with the apeture ring when moving from O to C in t...
Posted by Donut on 04/02/2009 - 14:45
Sunagor 500mm "telescope"
You set the aperture to the desired value and then focus when it's (O)pen, then (C)lose it down to actually take the photo. Never used one though, it'll be interesting to see your results. :)
Posted by hefty1 on 04/02/2009 - 14:51
Suggestions plz for 500mm lens
It depends on what you're photographing and what your requirements are. Do you want a zoom or a prime? Would an old manual mirror lens suffice? For that kind of money, perhaps the latest Sigma 150-500mm would be the best to look at for overall versatility (especially that it sports HSM). Just be ...
Posted by chirpy on 04/02/2009 - 17:31
Am I using my 50mm A F1.7 correctly?
Hi there, Got one of these off eBay for £53 - in mint condition so am very pleased. Managed to work out the auto aperture bit, but what I was wondering was whether the lens / camera automatically knows when the centre of the picture is in focus? I am half pressing the autofocus and then adjus...
Posted by jkharmer on 05/02/2009 - 19:57
Am I using my 50mm A F1.7 correctly?
If you have the body set to AF the shutter will only fire when the image is in focus. On MF mode it will fire no matter what. They both have their uses with manual lenses. Yes, you have the whole thing worked out there.
Posted by Tyr on 05/02/2009 - 20:08
Am I using my 50mm A F1.7 correctly?
Yes, the green hexagon indicates that the camera thinks the centre of the image is in focus, no matter what lens is attached. To take a shot with an MF lens, you can use manual focus mode, or auto focus mode any time with Catch-in-focus* turned off, or auto focus mode when the image is in focus o...
Posted by iceblinker on 05/02/2009 - 20:14
Am I using my 50mm A F1.7 correctly?
If you have the body set to AF the shutter will only fire when the image is in focus. K20D is different from the K10D in that it has an option to allow the shutter to fire in AF mode even when the image is out-of-focus. It conveniently saves having to remember to switch to MF mode for MF lenses.
Posted by iceblinker on 05/02/2009 - 20:18
SMC Pentax-FA 35-80mm F4-5.6
[quote:3496ace15f="johnriley"]What makes you think it's a pretty dismal lens? It makes it sound like the pictures will be a dirty grey unfocused mess! /quote] Hi John, The few mentions I can find of it are all quite negative :lol:, will do some test`s and report back. Dave
Posted by davex on 06/02/2009 - 10:07
Macro Magnification
It has nothing to do with the speed. A 1:2 lens is not a true macro lens. A 1:1 or a 2:1 are true Macro lenses. It is all to do with the construction of the lens and the number of elements which affect the magnification the lens provides. To be a Macro lens the lens must show the subject at at lea...
Posted by bforbes on 06/02/2009 - 20:38
Macro Magnification
No, a 1:2 500mm is not the same as a 1:1 1000mm. The size ratio is the physical size of the image on the film frame (or sensor) in relation to actual size of the object. So a 1:1 macro gives the same sized image on the film as the object measures in real life. A 1:1 macro gives you a life sized i...
Posted by MarkD on 06/02/2009 - 21:05
Macro Magnification
It's very simple. A 1:1 100mm Macro lens will focus down to half the distance a 1:2 Macro 100mm will. Macro lenses just focus closer. They achieve this with much longer focusing mechanisms, hence the size, weight and cost. The design is different too, emphasising closer distances and flatness ...
Posted by johnriley on 06/02/2009 - 22:38
Macro Magnification
So what are the differences between a 28mm, 50mm and 100mm macro lens? I am sure it can't be so but wouldn't the best be the longest? A 28mm, 50mm or 100mm macro lens is the same as any other 28mm, 50mm or 100mm lens except that they allow much closer focusing allowing --- if they are "true" macro l...
Posted by womble on 09/02/2009 - 20:49
DA 12-24mm advice
Hmmmm... shooting wide open isn't the best way to judge the sharpness of any lens ;) You really want to test around f/8 at least, and check both the centre and the edges (not just the edge as you've shown) since there can be differences in sharpness according to region. I've had both very sharp ...
Posted by MattMatic on 07/02/2009 - 10:07
DA 12-24mm advice
There are lots of Pentax lenses and the poorer ones we note as such, but sometimes it depends on what the lens is designed for. For example, the SMC Pentax-M 120mm f2.8 is soft at wider apertures. That's because it was designed to be so, as a portrait lens where cruel sharpness is not what we alw...
Posted by johnriley on 07/02/2009 - 11:11
DA 12-24mm advice
It would be a mistake to just evaluate sharpness when considering a lens ;) There are other factors (some that are especially important in super wides like the 12-24). The 12-24 is an excellent lens, and I wouldn't part with mine :D Colour and flare handling is stunning. e.g. http://www.ephotoz...
Posted by MattMatic on 07/02/2009 - 11:12
DA 12-24mm advice
Rob, I'm not sure what your focus point was here but it almost certainly wasn't the rear light. As the others have said testing a lens at it's largest aperture is not a reliable way of testing a lens. Also iso400 isn't going to retain as much detail as iso100 due to noise control smudging the detail...
Posted by RR on 07/02/2009 - 13:19
DA 12-24mm advice
Agreed about the focus accuracy Pete. In fact the first thing I do when I get a new lens is whip out the focus chart. I then make the necessary adjustments if required, before firing off some real-world test shots.
Posted by RR on 07/02/2009 - 14:02
DA 12-24mm advice
Its difficult to tell exactly but it looks to me as if the centre of the picture (just below middle of rear door window) includes a REFLECTION. Centre point AF was used so focus could be on the reflection NOT the car - if so tail lights of car could simply be outside of the depth of field. I would ...
Posted by Bob and his Pentax on 08/02/2009 - 16:09
Pentax FA 50 f1.7 at ffordes
The 1.7 is a bit smaller and lighter than the 1.4 as well. £99 is a fair price considering the rarity. They'd get even more if they put it on eBay! Hmmm! I've got a FA 1.4 and an F 1.7 right here in front of me and they look about the same size. The AP test report (1991) says they weigh 235g and ...
Posted by shim on 07/02/2009 - 15:31
Pentax FA 50 f1.7 at ffordes
"About" the same size ain't exactly the same size ;) http://www.bdimitrov.de/kmp/lenses/primes/normal/index.html : FA 1.4: 63x37mm, 220g FA 1.7: 63x31mm, 170g ... But in this case I think bdimitrov is wrong. Mine are both 64mm dia x 37.5mm back plate to front at infinity and 45.2mm at the othe...
Posted by GlynM on 07/02/2009 - 16:13
