Search results for 'back focus' - page 700
Which tele zoom lens to buy?
There is little point in a macro function on a zoom lens. It will not make the lens anywhere near as good as a proper macro lens, and it's easy enough to use a couple of extension rings if you need to focus closer. Extension rings should be in everybody's bag, in my view. G
Posted by George Lazarette on 27/02/2008 - 10:50
Objective Lens Reviews
Thanks to all for the links and information - greatly appreciated! Now to digest it all. I will also be able to experiment with my existing pentax screw mount lenses if I find an adapter. The general consensus seems to be that you need the genuine Pentax adaptor, it allows infinity focus (not all 3r...
Posted by hefty1 on 27/02/2008 - 23:20
Devilry with an old Minolta lens…
I modified the mount of an old (but very sharp and clear) Minolta Rokkor-PF 1:1.7 f=55mm lens for use with the K10D. The Minolta lens focusing is done by moving the whole optic´s (5 glasses) front and back in a 11 mm travel for the complete focusing range (from minimal focus distance; 40 cm to in...
Posted by dirk1000 on 28/02/2008 - 01:05
Devilry with an old Minolta lens…
If a lens can be made to focus its light on the film/sensor plane then it can be used. A lens is a lens. What the result will be will depend on the lens design.
Posted by johnriley on 28/02/2008 - 07:49
Devilry with an old Minolta lens…
The results using the modified Minolta lens in the K10D are confusing. The new minimal focus distance is now 30cm (minimal focusing stop) and the maximum in-focus target distance (at infinite stop) is no more than 1 meter and 10 cm away from the camera. This would imply that the lens is too far away...
Posted by stevo on 28/02/2008 - 17:54
Devilry with an old Minolta lens…
Yes, if the lens-to-flim/sensor plane is different in Pentax and Minolta SLRs there will be a discrepancy. This tends to result in closer focusing and no infinity focus.
Posted by johnriley on 28/02/2008 - 17:57
Devilry with an old Minolta lens…
Thanks John, thanks Stevo, I understand the problematic more clear now. Surely my lens stops a little (perhaps 0.5 mm) far away from the sensor plane when focus to infinite. And this is very well comprehended when I see the logarithmical scale in the focusing lens ring. For the closer distanc...
Posted by dirk1000 on 28/02/2008 - 21:19
Devilry with an old Minolta lens…
Well, the distance needed to move the lens for focus at infinite was not so depreciable. I moved the lens 3 mm back (to the sensor) and I need to do a fine adjust, another 0.5 mm, but for do this I need the help of a lathe to get this little distance! But at least, now I can shot at infinite (wit...
Posted by dirk1000 on 01/03/2008 - 03:12
Help!!
A few definitions are here: www.bdimitrov.de/kmp/technology/lens_terms.html The rest: AF = Auto Focus SDM = Supersonic Dynamic Motor (motor built into lens) DA = Digital Auto (I guess) Tamron's "Di" just means the lens has coatings suitable for use with digital cameras. ...
Posted by iceblinker on 28/02/2008 - 08:59
50-135mm F2.8 ed (if) da* sdm
I have the chance to buy a secondhand one. Is it as good a lens as I hope? Its a cracker Gywn, and yes it does have the dual focus. But don't dip into your K20 fund :lol:
Posted by Clarky on 29/02/2008 - 21:41
How do you choose between macros?
This maybe a very silly question, but maybe some one has some images to demonstrate. Why would you choose the new 35mm macro versus the DA 50mm or DA 100mm? I appreciate the angle of view is different, leading to closer focussing. But if all three offer 1:1 magnification, isn't it just the de...
Posted by Miles1010 on 04/03/2008 - 17:40
How do you choose between macros?
Well thanks for the answers. I thought that a wider macro would give a greater depth of focus. I really like the toadstools Dan. Including a background like that in macro shots is not something I've seen too often. Cheers. Peter
Posted by Miles1010 on 04/03/2008 - 19:43
How do you choose between macros?
Like most things, there has to be a compromise. I have just bought the Sigma 70mm macro, this is one of the first shots I have taken so I am still learning how to get the best out of it. Taken at F2.8 to see how shallow the depth of field is (very shallow as you can see) I chose this foc...
Posted by MX veteran on 04/03/2008 - 22:25
How do you choose between macros?
mxuser, To early yet to say anything much, except that it is a lot easier to handle than when using extension tubes, because of course you can focus on any distance from infinity down. It's my first macro lens and there are probably a few tricks I need to learn :?
Posted by MX veteran on 05/03/2008 - 17:59
Info on Pentax-A 70-210mm zoom please
I have just been given an SMC Pentax-A zoom 1:4 70-210mm macro. :D It is, I suspect at least 20 years old and despite a search of the internet I cannot find any detailed spec for it. Perhaps someone on the forum can help. I presume that the aperture at full zoom is 5.6 (that much I gleaned fr...
Posted by old timer on 05/03/2008 - 11:29
Info on Pentax-A 70-210mm zoom please
It indeed is 0,25x at its' clostest setting: it's the same magnification ratio on 70 (+macro setting) as it is on 210 (1,2 m closest distance), but you do well to use it at the 70 setting then, as sharpness declines rapidly once you go under 2m distance (@210.) I had it back in my film days, and ...
Posted by Pentaxke on 14/03/2008 - 19:03
Info on Pentax-A 70-210mm zoom please
I have this lens and the the lens can zoom by it self (gravity) because it works so smooth. The macro position is only available in the 70mm position and locks the in the 70mm position. So you can focus but you can't zoom The image is about the same size as in the 210mm at closest focusing distant....
Posted by gerard_bekking on 25/02/2016 - 00:34
pentax f2.8 40-80 lens
sad to see this... and how about the back of lens?
Posted by werk on 06/03/2008 - 04:08
pentax f2.8 40-80 lens
sad to see this... and how about the back of lens? Sorry no pic of the back of the lens. Can you post a pic of your lens :?:
Posted by Clarky on 06/03/2008 - 04:24
sigma 18-50 ex - problems! again! Anyone else experiencing!
Hi All, this problem has turned me - a relatively young man into a doddering wreck!! Despite fiddling with the software internals I still get bad back focus issues. Does anyone else have this lens? Up to F4 seems the worst but then the bigger focus "net" seems to hide it. Can a...
Posted by Bluewhistle on 06/03/2008 - 13:50
