Search results for 'sensor cleaning' - page 133
Lens Formulae
in fact at 18mm the image principal plane must be at least 25mm behind the rear element, I mean on a pentax slr, where the lens mount is 46mm in front of the sensor/film plane, and the rear element of the lens can't be more than a mm or two closer than this.
Posted by SpottyDog on 01/06/2011 - 18:20
A few q's about the Sigma 30mm, eBay and Sigma sevice before I buy...
Manual focus: I can't agree that f1.4 lenses are difficult to focus, that one's a complete mystery to me. The limited DOF means that the sharp point snaps in and out beautifully and alo the brighter image makes it easier as well. When you stop down to f8 or whatever, all that's happened is that the ...
Posted by Smeggypants on 29/05/2011 - 01:22
Changing Pattern of Lens Range
It is apparent Pentax has little interest in making fast lenses and there are some good reasons why. 1. Higher attainable ISO values reduce the need for speed for the purposes of low-light photography. 2. Most shooters rely on auto-focus mechanisms that have a hard time past a certain aperture...
Posted by Smeggypants on 30/05/2011 - 02:18
Changing Pattern of Lens Range
It's true that faster than f/2 can produce some interesting effects, but these are gimmicks in the same way adding effects in PP is a gimmick. Some might like them for aesthetic reasons but it is hardly a reflection of true optics. This is hard for me to understand. I have always thought of aperture...
Posted by Pentaxophile on 30/05/2011 - 12:12
Changing Pattern of Lens Range
You are not wrong, but my point is based on optical design. For every stop you increase light the aberrations go up by a factor of nine. It becomes almost impossible to control these beyond a certain point, which is why very fast (significantly faster than f/2) lenses generally have all sorts of odd...
Posted by rparmar on 30/05/2011 - 13:54
Phoenix 28-210mm Lens
A number of years ago I decided to buy a Pentax K100D DSLR. Since the Digital age of photography has arrived I've always wanted a DSLR instead of a Pentax K1000 35mm that I used for a few years before. The DSLR works real nice and have also purchased 3 different Lens's to use with it. However, ...
Posted by Corker2211 on 30/05/2011 - 18:54
Phoenix 28-210mm Lens
Unless the lens has an "A" setting on the aperture ring then you need to go into the DSLR menus and find the custom setting relating to aperture ring. Set this to "allow" (or "permitted", not 100% sure of the exact wording) and you'll be able to fire the shutter with this lens. You also need to look...
Posted by Dangermouse on 30/05/2011 - 22:12
Pentax 60-250 Problem
Have you tried cleaning the contacts on the lens and the camera? That would be my first step. The 60-250 has SDM focussing I think so those contacts should be included. Also, make sure you have the latest firmware in the camera perhaps. I used to have a K10d and that required a certain update to the...
Posted by matwhittington on 03/06/2011 - 06:26
recommend a macro lens please
One of the few things I used to use 1:1 for was slide copying. What sort of macro do you want to do? Remember 1:1 in in the sensor so an object will appear life size on the sensor and therefore much bigger on the screen or printed (unless you print very small ;) ) So a photo of a bee of a fly wil...
Posted by Kim C on 06/06/2011 - 16:38
DA 35mm f2.4 on 35mm Film SLR
I've given it serious thought. The sensor on my K-m has to be better than that on a £99 film scanner, the only thing I'm not sure about is whether there'd be a problem with crop factors (duplicators designed for 35mm cameras, not APS-C sensors)?
Posted by Dangermouse on 05/06/2011 - 17:16
DA 35mm f2.4 on 35mm Film SLR
I've given it serious thought. The sensor on my K-m has to be better than that on a £99 film scanner, the only thing I'm not sure about is whether there'd be a problem with crop factors (duplicators designed for 35mm cameras, not APS-C sensors)? I briefly owned one of those duplicators, and the resu...
Posted by thoughton on 05/06/2011 - 19:23
Tamron 70-200mm f2.8 and 2x
Hi Sue, I won'i be much help here sorry. I don't own the Tamron 70-200 f/2.8 but have 4 TC's, 2 of them are Teleplus SHQ models 1.5x and 1.7x and work well with DA*200 and DA*300 SDM lenses although they tend to hunt a little depending on conditions. I have a Teleplus 2x MC7 (not DG) this will not w...
Posted by johnwhit on 07/06/2011 - 18:29
Opinions sought on Sigma 8-16mm F4.5-5.6
Well the 15mm seems to give a little more contrast but the Sigma looks sharper to me. Overall there doesn't seem to be much in it at all. I'd concur with that, I also notice I have dust on the sensor:lol: The Sigma is a little sharper at the edge in particular with less CA:shock: John
Posted by johnwhit on 18/06/2011 - 20:13
Kit list for Western USA trip?
In my extended wanderings around the SouthWest, my most-used kit includes: DA18-250 walkaround (large spaces), Tamron 10-24 walkaround (small spaces), DA10-17 fisheye (unique angles), FA50/1.4 (dark places). I will minimally have a Raynox DCR-250 also, and some other macro setup, often a couple de-g...
Posted by RioRico on 29/06/2011 - 00:47
Macro lens (WHICH ONE )
I use the Sigma 70mm f2.8 MACRO, you can pick them up fairly easily and they double as a fantastic portrait lens as it equates to 105mm on a crop sensor. Never had any issues with mine either, built like a tank and cost less than £300
Posted by claudefrog on 22/06/2011 - 14:56
Lens for Street Photography
Vignetting shouldn't be too bad at all on APS-C sensors. I think it was tested on a Canon APS-C sensor which is marginally smaller than the K-7 sensor.
Posted by wadna on 23/06/2011 - 02:43
Lens for Street Photography
I envisage people subjects often being on the edge of the frame because I will be in close aiming to one side to fool them into thinking they aren't in the shot. Ah, well you got me there, the only lens I could recommend would be the Zeiss 18mm f/3.5, I don't think anything else would compare edge s...
Posted by johnwhit on 28/06/2011 - 08:15
Lens for Street Photography
I envisage people subjects often being on the edge of the frame because I will be in close aiming to one side to fool them into thinking they aren't in the shot. Ah, well you got me there, the only lens I could recommend would be the Zeiss 18mm f/3.5, I don't think anything else would compare edge s...
Posted by wadna on 28/06/2011 - 08:38
FA 43mm ltd or Sigma 50mm 1.4 or DA* 55mm 1.4
But there's absolutely nothing wrong with the build quality of the FA 50mm. Absolutely, I have a bag full of FA lenses, never had any problems with them, they're light compact and take regular filters, can be used on film as well as digital, less vignetting than crop sensor lenses and use the sweet ...
Posted by johnwhit on 23/06/2011 - 08:53
FA 43mm ltd or Sigma 50mm 1.4 or DA* 55mm 1.4
On an APS-C sensor the digital equivalent of the 85mm f1.4 is of course the 55mm f1.4 lens. The digital equivalent of the 50/55mm standard lens is the 35mm f2.4, which is the low priced standard lens that quite a few users were asking for. The classic 135mm lens would be something like a digit...
Posted by johnriley on 23/06/2011 - 08:55
