Search results for 'back focus' - page 1095
Manual focus zooms on dslr question
Gary, I know many people may disagree but I think that your premise that having a cropped sensor with respect to full frame or 35mm film cameras leads to some form of magnification is incorrect. Having a smaller sensor I my opinion simply leads to capturing a cropped image of the scene. I think it ...
Posted by DoctorJeff on 14/07/2013 - 11:25
Manual focus zooms on dslr question
Thanks Jamie and Rob - very helpful. And hopefully this will cover 456's original question ! Jamie - I will have a proper read of those articles... thank you. I was aware of the concept of cropping resulting from the sensor being smaller than a 35mm film plane, but have misunderstood the concept o...
Posted by GaryJohn on 14/07/2013 - 11:26
Manual focus zooms on dslr question
EFL (equivalent focal length) is sometimes given, to give people an idea of how a lens would look on 35mm. But the true focal length remains what it is, regardless of crop factor, and this should be the focal length stated on the lens barrel not the 'EFL'.
Posted by Pentaxophile on 14/07/2013 - 11:47
Manual focus zooms on dslr question
Geoff, I used to own the Olympus 70-300mm. Here's an image of it. The 140-600mm equiv is in blue and the lettering is at least twice the size of the 70-300mm. I always felt that this was nothing other than an advertising gimmick. I've never compared 35mm and cropped sensor performance using...
Posted by jamieallan on 14/07/2013 - 11:53
Manual focus zooms on dslr question
So I need to change the focal length every time I zoom in or out?
Posted by fourfivesix on 14/07/2013 - 15:15
Manual focus zooms on dslr question
So I need to change the focal length every time I zoom in or out? If you want to use the SRS to it's best advantage, yes you do. If you turn the SRS off, you don't need to dial in the focal length. A good rule of thumb is for hand held photography is: keep your shutter speed at or above the the ...
Posted by doingthebobs on 14/07/2013 - 17:15
Manual focus zooms on dslr question
Jamie, Any lawyer will tell you it is all in the wording. I do have to agree with you that it looks like a bit of a gimmick on that lens. Now, just out of arm's reach I have a P50, fitted with a Tamron Adaptall-2 in 17mm F2.5. When I stick that lens on my K20D it behaves like a 24mm (really, it s...
Posted by DoctorJeff on 14/07/2013 - 18:25
Manual focus zooms on dslr question
So I need to change the focal length every time I zoom in or out? Ideally yes. In practise, it's a pain. I dial in the shortest focal length e.g. 75mm on the 75-150mm. Better too little SR than too much, I think (although I have not tested this!)
Posted by Pentaxophile on 14/07/2013 - 18:55
Manual focus zooms on dslr question
On P.142 of the K-5 user manual, with regard to a manual lens, it tells you to set the value closest to tha actual focal length of the lens, and for a zoom lens set the value closest to actual focal length at the zoom setting being used. Philip
Posted by MrB on 14/07/2013 - 19:46
Manual focus zooms on dslr question
Thank you MrB, you beat me to it. The instruction manual is a wonderful source of information!
Posted by johnriley on 14/07/2013 - 21:58
Manual focus zooms on dslr question
Yes John, as the saying goes - if all else fails, read the instructions! :D And for anyone who needs a user manual, they are here for Pentax digital cameras - http://www.pentax.jp/english/support/download_manual.html Cheers. Philip
Posted by MrB on 14/07/2013 - 22:29
Manual focus zooms on dslr question
Jamie, I did find your quote from Ansel Adams interesting, in that a 1980 publication pre-dates the Sony Mavica by a year, the Nikon SVC by 6 years, and the Kodak KAF-1400 M1 (generally considered as the first usable DSLR) by 8 years. The statement about the image not being magnified is of course ...
Posted by jamieallan on 14/07/2013 - 23:05
Manual focus zooms on dslr question
One other thing to note is that, if you think you won't have time to change the focal length setting on the shake reduction, then set it to the shortest focal length that you will be using. The amount that shake affects the image is related to the focal length - if you tell the camera that you have ...
Posted by Cuchulainn on 15/07/2013 - 09:44
Manual focus zooms on dslr question
One other thing to note is that, if you think you won't have time to change the focal length setting on the shake reduction, then set it to the shortest focal length that you will be using. The amount that shake affects the image is related to the focal length - if you tell the camera that you have ...
Posted by gwing on 15/07/2013 - 13:49
Manual focus zooms on dslr question
Mathematically, over-compensating shake reduction is going to give no more and no less error than under-compensating the same amount. As far as I know nobodody has done any tests to show that practice is different to teory - so I would assume it makes no difference which way you go - just set th...
Posted by Cuchulainn on 15/07/2013 - 14:00
Manual focus zooms on dslr question
The easy way to avoid over-compensation is to switch it off. If you only use shake reduction when you need to, setting the lens focal length accurately isn't a very onerous task. Andrew
Posted by andrewk on 15/07/2013 - 14:33
Manual focus zooms on dslr question
Jamie wrote: I'm sorry but I don't understand your last two sentences - I can't see where magnification comes into it - it's the laws of physics and consequently the decrease in field of view seen through the smaller sensor. I guess that you are having a little problem with the "laws of physics" Ja...
Posted by DoctorJeff on 15/07/2013 - 23:40
Manual focus zooms on dslr question
Mathematically, over-compensating shake reduction is going to give no more and no less error than under-compensating the same amount. As far as I know nobodody has done any tests to show that practice is different to teory - so I would assume it makes no difference which way you go - just set th...
Posted by johnha on 16/07/2013 - 00:16
Manual focus zooms on dslr question
Jamie wrote: I guess that you are having a little problem with the "laws of physics" Jamie. The focal length of a lens determines the acceptance angle of that lens. In lay terms, that is it's "seeing angle". Because there is a difference in the size of the sensor between 35mm and a DSLR (and i...
Posted by Cuchulainn on 16/07/2013 - 09:17
Manual focus zooms on dslr question
Geoff, Here's an illustration that hopefully sums up the discussion http://www.google.co.uk/imgres?imgurl=http://www.blogcdn.com/www.engadget.com/media/2011/12/digitalsensor-sizes.png&imgrefurl=http://www.engadget.com/2011/12/16/engadget-primed-why-your-cameras-sensor-size-matters/&h=208&w=310&s...
Posted by jamieallan on 16/07/2013 - 09:45
