Search results for 'back focus' - page 1098
Calculating depth of focus
Sounds good to me Nigel.
Posted by johnriley on 23/07/2013 - 19:29
Calculating depth of focus
You seem to assume the negative meaning, John, but - argue to present supporting or opposing reasons or cases in a dispute; to try to prove by presenting reasons; to debate or discuss; to persuade; to give evidence; (World English Dictionary) which, as you have stated, is what we have been doi...
Posted by MrB on 23/07/2013 - 19:43
Calculating depth of focus
I haven't quite grasped any specific dispute or argument here yet, as in specific opposing views. Its been informative for sure. So if we seem to be agreeing that the actual lens 'DOF' remains constant, is it the case, (as MrB has said), that lens DOF scales will only be correct when applied to a...
Posted by McGregNi on 23/07/2013 - 21:52
Calculating depth of focus
At best, DOF scales on lenses are notoriously inaccurate. They are good enough for a rough and ready evaluation of the hyperfocal distance, but I would always stop down one stop further than they suggest for the optimum result. Now stop down mechanisms I find unusable as the ground glass screens ...
Posted by johnriley on 23/07/2013 - 22:04
Calculating depth of focus
The marking on many older lenses will be designed for full frame (film) use where the image is often only printed as a 6x4. These days only a portion of that image is recorded and that is often viewed bigger so it's not surprising the markings are inaccurate for modern use. I used to find them qui...
Posted by petrochemist on 23/07/2013 - 22:51
Calculating depth of focus
Phillip, I remember a good discussion on this subject a few years back on Digital Photography Review. To understand DOF you must understand that it originally related to a given print size enlarged from a negative. We can now refer to a print size or screen image, but the relevance is still the ...
Posted by pschlute on 24/07/2013 - 12:30
Calculating depth of focus
At best, DOF scales on lenses are notoriously inaccurate. They are good enough for a rough and ready evaluation of the hyperfocal distance, but I would always stop down one stop further than they suggest for the optimum result. Agreed - especially when using them on an APSC sensor. But for all thei...
Posted by gwing on 24/07/2013 - 13:33
Calculating depth of focus
Just to put a Pentax-specific practical slant to this, here is my method for eyeballing focus accurately. This is most useful perhaps for wider angles and tripod work, and in lighting conditions when it is hard to see your focus point clearly through the viewfinder. Firstly I frame up the scene u...
Posted by McGregNi on 24/07/2013 - 21:31
Calculating depth of focus
Just to put a Pentax-specific practical slant to this, here is my method for eyeballing focus accurately. This is most useful perhaps for wider angles and tripod work, and in lighting conditions when it is hard to see your focus point clearly through the viewfinder. Firstly I frame up the scene u...
Posted by simonkit on 25/07/2013 - 22:55
Calculating depth of focus
Once upon a time, depth of field and hyper-focal-distance was relatively straightforward to work out. Now with the advent of digital, crop factors and lack of DoF scales on lenses, it appears to have become more complicated. Maybe this should be sticky!
Posted by Defragged on 26/07/2013 - 00:13
Calculating depth of focus
But how lucky we are now to have all these extra electronic aids and alternative techniques to employ ! Even without using any lens scales, my focussing is more accurate now on Pentax than ever before, even at 14mm, and I can try different methods depending on the type of scene and lighting levels.
Posted by McGregNi on 26/07/2013 - 08:40
All around lens choice
You already have a 18-55mm which is a very good lens and perfectly adequate for the 'walk about' use you have mentioned. It is also capable of taking excellent landscape shots if used correctly - keep it around F7.1 to F11 and it will be sharp. I you are going to keep the 18-55 (which I think yo...
Posted by davidstorm on 23/07/2013 - 21:25
All around lens choice
A 14mm is a specialised lens though Nigel. A 55-300mm isn't. If we want pictures of birds or sporting events, we'll need the reach. Looking at your lens list, would it be fair to say you're more of a wide angle to standard lens photographer? Yes, I am for sure. As I said earlier, after getting th...
Posted by McGregNi on 24/07/2013 - 16:38
All around lens choice
When it comes to a budget telephoto, I can vouch for the 1980's Tokina SDII SZ 70-210. I got a pristine copy on Ebay for £40 ( and I've seen others). It's manual focus with PKA mount and takes excellent pictures. One of the original selling points was lack of chromatic abberations, and it's true. Al...
Posted by RussV on 05/08/2013 - 09:10
All around lens choice
I always remember when I got my first Sigma 70-200mm f2.8 from a seller on Ebay, it came with a Hoya filter. When I tried the lens every shot was slightly out of focus and just lacking the quality I expected so I was all ready to file a complaint and get a refund when I thought I would remove the fi...
Posted by Mike-P on 18/09/2013 - 09:58
All around lens choice
I always remember when I got my first Sigma 70-200mm f2.8 from a seller on Ebay, it came with a Hoya filter. When I tried the lens every shot was slightly out of focus and just lacking the quality I expected so I was all ready to file a complaint and get a refund when I thought I would remove the fi...
Posted by Mongoose on 18/09/2013 - 16:29
Cycle Events - DA 55-300??
Andrew, I used the 17-70 at the Olympics and found that quite good for the triathlon bikes. If you can get them head on then the 55-300 should be ok if you pre focus, you may struggle for panning shots with this though as you'll be quite close to the action. George
Posted by carmagw on 23/07/2013 - 19:17
Cycle Events - DA 55-300??
Andrew, I used the 17-70 at the Olympics and found that quite good for the triathlon bikes. If you can get them head on then the 55-300 should be ok if you pre focus, you may struggle for panning shots with this though as you'll be quite close to the action. George May go with the 17-70 then Geo...
Posted by AndrewA on 23/07/2013 - 19:28
longer range
Don't even think of using a cheapish consumer 50-200 zoom with a converter as it won't work, specifically it won't autofocus and even if you manually focus the image quality from a cheap zoom stretched with a convert is likely to be poor. Converters work best on fast (f2.8, possibly f4) high quali...
Posted by gwing on 25/07/2013 - 11:59
Tamron 28-75 f2.8 or Sigma 17-70mm f2.8-4?
The tamron is not fast to focus in low light, the sigma probably focuses faster but you lose the wider aperture at the long end....
Posted by cabstar on 28/07/2013 - 20:56
