Forgot Password
Pentax Camera Forums Home
 
Log in or register to remove ads.

Showing results 1 to 8 of 8 Search:
Forum: Photographic Technique 09-13-2013, 04:19 AM  
Light Meter apps
Posted By JoWac
Replies: 15
Views: 1,967
EV simply represents specific shutter/aperture combinations in a single number
Forum: Photographic Technique 09-13-2013, 04:08 AM  
Light Meter apps
Posted By JoWac
Replies: 15
Views: 1,967
Most light meters will in fact return the EV, based on the measured LV and the selected ISO.
Forum: Photographic Technique 09-12-2013, 11:48 PM  
Light Meter apps
Posted By JoWac
Replies: 15
Views: 1,967
I suspect that there is some confusion between EV and what is termed LV which is less well defined. Exposure versus light value.
A light meter will effectively measure the LV (or lux) and the photographer then determines a particular EV depending on the ISO.
EV refers strictly to the exposure value set on a camera (shutter speed and aperture only) and LV indicates the amount of light present.
On some Synchro-Compur shutters one can set a particular EV value and then alter either aperture or shutter speed and the system will adjust the other variable accordingly, keeping the exposure constant. Like pressing exposure lock to fix the EV and then changing the combinations of aperture and shutter speed, maintaining constant exposure.
LV matches EV for correct exposure at 100 ISO.
Thus, for any metered LV, the required EV for proper exposure will change depending on the ISO.
Forum: Pentax SLR Lens Discussion 05-18-2013, 08:11 AM  
Macro recommendation
Posted By JoWac
Replies: 17
Views: 2,093
Any macro capable lens should suffice, i.e. macro lens or normal lens with extension etc. Maybe use existing lenses to determine best focal length. Just look through, even if the image is severely out of focus, and see which focal length gives about the right view. Use a rubber lens hood pressed against the glass, and reflections from flash or other lighting will not be a problem. Flashes could then best be positioned to the side or even overhead, rather than head on - particularly since particles in the water could reflect back.
Forum: Pentax SLR Lens Discussion 05-09-2013, 08:07 AM  
Help choose between DA* 200, 60-250, 300
Posted By JoWac
Replies: 35
Views: 5,071
Apropos magnification compared to binoculars:
The K20 spec lists x0.95 viewfinder magnification with a 50mm lens. That fits, because with a 50mm lens, the size of an object with one eye through the viewfinder and the other eye open, is almost the same. So, a 400mm lens would provide around 8x magnification when viewing through the camera (actually 7.6x = 400 / 50 x 0.95), when compared to binoculars or a telescope. This is also the commonly claimed magnification for telephoto lenses when used on 35mm where 50mm was typically viewed as the standard lens. Whether you wish to further include a crop factor for APS-C, is really a question of how much you are prepared to enlarge your taken image.
Forum: Pentax K-5 & K-5 II 03-28-2013, 01:12 AM  
SR-difference between K-5 and K-5 II
Posted By JoWac
Replies: 8
Views: 1,914
I have a similar problem with my K20. Usually the SR works very impressively for my 400mm lens, but when I try to hold it really steady, maybe by resting on something, the SR sometimes produces a double image. It is generally recommended to switch off SR on a tripod, and it seems that sometimes, when holding the camera really still, the SR (mis)behaves as if the camera is tripod mounted. I struggle to determine the threshold point, and have lost images due to this. Maybe you are experiencing something similar and just holding the new camera a fraction too steadily on that day? Perhaps there is some slight variation in the SR activation threshold between cameras?
Forum: Pentax SLR Lens Discussion 02-13-2013, 05:20 AM  
"Best" K-Mount Macro Lens for $200 or Less?
Posted By JoWac
Replies: 25
Views: 16,181
I only note one mention of the 100/4, which in this part of the world is relatively common and can usually be had for (well) under $100.

I have used this lens (formula) in the form of the bellows Tak (from 1966) and am still using the SMC-T version on bellows as well as the A100/4 for more general use.

Optically I would rate them all as excellent, certainly when stopped down a bit, which you normally would for macros. (Nikon guru, Bjorn Rorslett rates the bellows Tak 4/5 and only criticizes flair, which has been reduced with SMC and later coatings)

It is relatively compact and light for a macro lens, which can be an advantage in the field. The only drawback for me is in general use due to the steep focusing at longer distances, with the next marking after infinity being at 3m, which makes manual focusing a bit more difficult than with e.g. the M100/2.8.

It only goes to 1:2 on its own, but with crop factor, relative to filling the frame, this disadvantage is mitigated a little.
As the bellows version proves, this is not an optical limitation, and this lens thus works very well with tubes and bellows extension, unlike some of the more modern floating element versions.
Focussing as a unit also has the advantage that there are no focal length changes when focusing closer, which helps this lens maintain a longer working distance than most 100mm macros.
It also performs much better with the old T6 teleconverter than the otherwise excellent Sigma 90/2.8 which features FREE and floating elements - this converter seems generally way better with old style unit-focusing glass.
Forum: Welcomes and Introductions 02-13-2013, 04:50 AM  
Greetings from JoWac in CT
Posted By JoWac
Replies: 1
Views: 518
Greetings All,

As a long time lurker (literally years) I have really enjoyed this forum.
Thanks to all of you for the pleasure, stimulation and many insights provided.
Have been using SP-F and SP-II with mainly slide film since school days in 1975 and moved to K series in the form of a battered K1000 only in 2003, simply because I stumbled across some bargain K lenses (A20, K28/3.5, A50/2 and A100/4 macro for $100). Subsequently found a new *istDL for half the cost of any other DSLR, which kept me with Pentax even for digital. Still use it, despite my main camera being a K20 since 2008, and am eyeing the K5II(s) since LBA is largely satisfied for now. Sold off most screw mount lenses, but am definitely keeping the 50 and 100 SMC macro Taks and bellows. I have a strong interest in macro, wildlife and landscape, with people (other than family) featuring more sporadically. Plenty scope here in Cape Town and further afield in southern Africa.
I have severe bandwidth restrictions and am thus not likely to upload many images, but look forward to following less anonymously, and even, occasionally, contributing ...
Best regards,
Jo
Search took 0.00 seconds | Showing results 1 to 8 of 8

 
Forum Jump


All times are GMT -7. The time now is 07:34 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top