Search results for 'back focus' - page 654
100mm Macro Quandry
The figures on the SMC Pentax-M 100mm f4 Macro do indeed refer to magnification and 2 means 1:2 In practical terms, macro lenses are specifically designed with a flat field and to give superb image quality when used close up. A 1:2 magnification, half life size, is usually referred to a macro, an...
Posted by johnriley on 19/10/2006 - 23:57
100mm Macro Quandry
Am I right in assuming that it would be a .75 magnification factor when used with my *ist Ds? Drew, This is an odd one, and depends on how you look at it! Compared to 35mm film, you will apparently have greater magnification. If you have a subject that is 48mm long, on film the image would be 24...
Posted by photo*ist on 21/10/2006 - 17:10
100mm Macro Quandry
Well, I did say "This is an odd one, and depends on how you look at it!" :D Drew, the minimum focusing distance of the lens is not going to change - it's the same lens whatever body it's mounted on, after all. The reaon you could see 65mm width on your MZ5N, is because that's roughl...
Posted by photo*ist on 21/10/2006 - 18:55
100mm Macro Quandry
I reckon that sounds right. :D Of course, the advantage of the digital body is that to get that increase in magnification (on the output :lol: ), you don't suffer from a loss of light (as you would using a 1.5x convertor) and you can still focus on infinity (which you would lose if using extension...
Posted by Daniel Bridge on 21/10/2006 - 19:14
100mm Macro Quandry
Computers, eh? Computers are wonderful when they are firing on all cylinders :D , but when they're not.... :cry: Still I wouldn't like to go back to the days of letter writing. How long would these forum discussions take? :shock:
Posted by johnriley on 23/10/2006 - 09:01
Auto Focus Lenses - The Long and the Short of It
Haven't seen a dumb question here for a while (I've been away and have been delinquent in my submissions). Sooooooo...... Now that I've entered the K mount reality with Don's Super Program and three wonderful M and A lens based on great advice from this forum, I thought I'd familiarize myself wit...
Posted by Anonymous on 24/10/2006 - 12:07
Auto Focus Lenses - The Long and the Short of It
there was a 28-70 f4 on sale at london drugs wpg (clearance item) for $149.00 Cdn a while back..want me to check to see if it's still there? it's a constant aperture zoom with internal focussing..{.both good things}. I was using the 28-200 on a super program and an me yesterday! and a 50 mm 1.4...
Posted by Don on 24/10/2006 - 12:26
Auto Focus Lenses - The Long and the Short of It
Mac, You assume correctly :D Pentax compatibility is probably the best there is ;) Though often the AF lenses require less rotation to focus, and the SMC-F have piddly little focus rings. Don't forget that wide angle lenses will have greate DoF too so focussing is less critical - but you knew ...
Posted by MattMatic on 24/10/2006 - 12:27
Auto Focus Lenses - The Long and the Short of It
I would probably resist buying AF IF (auto focus - internal focus) lenses if you plan to continue using them on a manual focus body. The reason is that the amount of movement required of the focus ring to travel from minimum focus to infinity is often very small. This can make it difficult to achiev...
Posted by Mannesty on 24/10/2006 - 13:05
Auto Focus Lenses - The Long and the Short of It
Thank you all! Most valuable input as always. Don, I've PM'd you re your kind offer. I feel the jump to AF is inevitable, as focusing through my ever-thickening tri-focals is becoming dodgy. Much as I hate to concede my beloved Spotmatics, and ME, I'm loosing too many shallow DOF shots (my...
Posted by Anonymous on 24/10/2006 - 13:57
Auto Focus Lenses - The Long and the Short of It
The 1:1.4 28-70 is a very good lens, by all accounts, but it suffers from element separation. Recently, Pentax in the US have said they can repair such lenses, but I don't know at what cost. My advice is not to pay much money for this lens. G
Posted by George Lazarette on 24/10/2006 - 13:58
Auto Focus Lenses - The Long and the Short of It
Mac, What you need is the Sigma KAF 50-200mm. It has built-in AF, and will therefore convert any Pentax K-mount MF body to AF. It's good for doing upper-body training as it's not light (it takes three batteries), and the AF takes a few minutes to lock on, but apart from that (and the poor opt...
Posted by George Lazarette on 24/10/2006 - 14:04
Auto Focus Lenses - The Long and the Short of It
Ohhh George...... Always the OEM fan! Thank's for the tip. Does element separation involve those pieces that are glued (spruce-gummed) together? I fear this would be a costly repair indeed! (Am now a Bowmore Dusk addict!)(I'll have to initiate Don!) Best!
Posted by Anonymous on 24/10/2006 - 14:15
Auto Focus Lenses - The Long and the Short of It
ROFL @ George :P Mac - no, George is referring to the second to last element's coating going all cloudy. It looks a bit like condensation, but it's permanent. I've had two 28-70s that have done this. One I managed to pull apart and scratch the resultant gunk off (fingernail and Eclipse solution) ...
Posted by MattMatic on 24/10/2006 - 15:02
Auto Focus Lenses - The Long and the Short of It
Eeekkk! Warning taken! Thank you!
Posted by Anonymous on 24/10/2006 - 15:24
Auto Focus Lenses - The Long and the Short of It
Mac, I'm just finding out what the estimated repair cost would be (as I have two of 'em already). When I find out I'll let you know ;) It's a good lens, if it weren't for that problem! Matt
Posted by MattMatic on 24/10/2006 - 15:33
Auto Focus Lenses - The Long and the Short of It
George You said something very interesting in this thread about a Sigma 50-200mm AF lens. I had one of these recently in Minolta fit, but without any electrical contacts on the mount how does it focus exactly? Three AAA batteries were housed in the body of the lens as you say, and it was a mon...
Posted by johnriley on 24/10/2006 - 16:23
Auto Focus Lenses - The Long and the Short of It
There is an AF button on the lens, and when you press it the lens focusses (slowly). Quite how it knows when it is in focus, I don't know, but it does work (slowly). I don't want to give anybody the wrong impression about this lens. It is possible that some readers might be under the erroneous...
Posted by George Lazarette on 24/10/2006 - 16:45
Auto Focus Lenses - The Long and the Short of It
Sorry George, Could you please clarify whether the Sigma lens that you refer to focuses quickly or slowly, I'm not sure you've quite got your point across. :D Dan
Posted by Daniel Bridge on 24/10/2006 - 18:02
Auto Focus Lenses - The Long and the Short of It
my 28-70 has been through H. E. L.....you get the idea. I've not had that problem....but then my macbook hasn't been frying eggs or shutting itself off, I threw a chain on my 130 hp motorcycle and only need an oil filter housing, chain and sprockets...the list is endless...maybe I'm just a lucky guy...
Posted by Don on 24/10/2006 - 21:43
