Search results for 'back focus' - page 1097
Calculating depth of focus
AP ran an article I believe in a recent issue (week b4 last I think) on maximising depth of field. It included depth of field tables for different apertures as well as instructions for calculating DoF. Might be worth locating a copy and having a read. Other than that, check out the 'DOFMaster Depth ...
Posted by Defragged on 22/07/2013 - 14:43
Calculating depth of focus
The rules and calculations are not simple but there are several free apps for smartphones to work out depth of field for you instantly after entering the camera, focal length, aperture and subject distance. E.g. For Android phones open Google Play and search for "depth of field calculator"; I expect...
Posted by MrB on 22/07/2013 - 15:04
Calculating depth of focus
Also 'diffraction' has to be a concern at this aperture surely. Fortunately, in practice it's not a problem and you'll get crisp shots at f/16. They won't be as crisp as the optimum aperture maybe, but still absolutely good enough. f/22 and beyond is another story, but if you need the DOF then, as a...
Posted by johnriley on 22/07/2013 - 15:04
Calculating depth of focus
Hi All and thanks John - I always understood that the proper term was, as you pointed out, depth of field but I remember a posting from a few months ago which stated depth of focus - but I may well have remembered incorrectly. Thanks for the 2 links - not quite what I had hoped but lenses are ...
Posted by eoinandpaula on 22/07/2013 - 15:17
Calculating depth of focus
You're probably are already of of these two points, but in case it helps I'll mention them... 1. Many of the older prime lenses actually show the depth of field available at each aperture such as this M50mm f2. Obviously this is harder to implement in a zoom lens. 2. Don't forget most DS...
Posted by JAK on 22/07/2013 - 17:19
Calculating depth of focus
If you are trying to get reasonable DOF with a long lens, particularly at close distances ... It is going to be impossible, DOF will always be shallow. To improve things as much as you can: a) Increase camera ISO to as high as you can tolerate noise-wise. b) Stop down the lens a bit. Changin...
Posted by gwing on 22/07/2013 - 17:36
Calculating depth of focus
If you have an iPhone I recommend TrueDoF it you input your focal lens' length then you use the slider for aperture and it will display the approximate DoF.
Posted by SteveEveritt on 22/07/2013 - 18:26
Calculating depth of focus
Many of the older prime lenses actually show the depth of field available at each aperture such as this M50mm f2. The depth of field scales on these older lenses assume a full frame image (35x24mm on film). However, with a Pentax K-series crop frame sensor (24x16mm), the actual depth of field is o...
Posted by MrB on 22/07/2013 - 20:26
Calculating depth of focus
If you have an android mobile have a look at the DOF CALC app, I use it all the time Simon
Posted by simonkit on 23/07/2013 - 09:30
Calculating depth of focus
Many of the older prime lenses actually show the depth of field available at each aperture such as this M50mm f2. The depth of field scales on these older lenses assume a full frame image (35x24mm on film). However, with a Pentax K-series crop frame sensor (24x16mm), the actual depth of field is o...
Posted by JAK on 23/07/2013 - 11:53
Calculating depth of focus
JAK has made a good point. The DOF at a given aperture will always be the same, regardless of the format behind it. What changes is the the field of view has changed, so to get the original image back needs a wider lens. Conversly, the cut down picture is now a mild telephoto shot with the same D...
Posted by johnriley on 23/07/2013 - 12:00
Calculating depth of focus
Most of the optics/maths of this are beyond me, but a D.o.F calculator gives different results for different formats. E.g. Using the one at Cambridge in Colour for a 50mm lens at f/8, focused at 8 metres - On 35mm (full-frame): Nearest Acceptable Sharpness: 4.41m Furthest Acceptable Sharpness: ...
Posted by MrB on 23/07/2013 - 12:46
Calculating depth of focus
But that's no good as a comparison, because the 35mm image is a standard lens and the ALS-C image is a telephoto lens. It's all about magnification, but the complication isn't really necessary in real life. Take a picture, look at it, magnify the image. If the bits you want are not sharp then use...
Posted by johnriley on 23/07/2013 - 12:55
Calculating depth of focus
A lens can only focus at one specific plane, anything before or after that is therefore not in focus. How acceptable that nearly in focus zone is depends on the intended use of the image (eg web or 12x15" print) and the viewing distance. At a web size the whole image may look acceptably sharp wherea...
Posted by JAK on 23/07/2013 - 12:59
Calculating depth of focus
The two Johns, Your points might be relevant to practical photography but fail to support the original point that was made, quote - "Many of the older prime lenses actually show the depth of field available at each aperture". The usefulness of that statement is challenged by depth of field calculat...
Posted by MrB on 23/07/2013 - 13:46
Calculating depth of focus
The two Johns, Your points might be relevant to practical photography but fail to support the original point that was made, quote - "Many of the older prime lenses actually show the depth of field available at each aperture". The usefulness of that statement is challenged by depth of field calculat...
Posted by JAK on 23/07/2013 - 14:38
Calculating depth of focus
Actually MrB, you're incorrect in your statement for the SAME focal length lens, at the SAME aperture, focused at the SAME distance, the depth of field is DIFFERENT on a different format and the bit you've missed is that under these circumstances each format will give a different picture. The DO...
Posted by johnriley on 23/07/2013 - 15:40
Calculating depth of focus
This is my final attempt. Firstly, as I have stated before, I do not understand the optics or maths of depth of field calculations, so I can only rely on information from those that (presumably) do. Secondly, the ONLY point I am trying to make is that the depth of field scale on an old lens ...
Posted by MrB on 23/07/2013 - 18:52
Calculating depth of focus
Nobody's arguing with you Philip, it's a discussion. :)
Posted by johnriley on 23/07/2013 - 19:17
Calculating depth of focus
So, if I understand correctly, what we are saying here is that for any single scene shot with a specific lens at a specific aperture, the DOF (the distance within the scene that appears in focus) does not change just because you take another shot with the same lens and aperture on another format. ...
Posted by McGregNi on 23/07/2013 - 19:27
