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Hi all,

Just looking for some help with Depth of Field. I understand it and know how it works. However where I struggle is what to set my aperture at for different shots. I really enjoy shooting with a low f number (1.8) but I know I need to increase this when I want to bring more things into focus or want to shoot a couple of people together.

I think with practice I will learn automatically what aperture to use for each shot. But is there a guide, or tips of things to think about. For example if I was shooting 2-3 people would f 2-3 be enough? I would normally crank it up to be sure and therefore sacrifice some ISO or increase lighting.

Any tips or help would be appreciated thank you.
 
It depends on the focal length. There are a lot of tools at DOFmaster that you can use. For the most common focal lengths I use, I printed out some tables and put them in the camera bag.

It's difficult to say that for 2 or 3 people you need f/x, because are those people in line, staggered or one behind the other? You need to be able to judge the depth of field you need (in cm or inches) and then have a rough idea what aperture is needed for that focal length to get it.
 
If you predominantly used fixed focal length prime lenses then you could print out a table for each from here.

http://www.dofmaster.com/doftable.html

However if you use zooms then to have a printed table for all focal variations would be impractical. What I find indispensible is an app for my iPhone called iDof calc just pop in your camera settings and you get an instant readout of nearest and furthest in focus range. There are lots of other good apps along these lines DoFmaster is another and they can be had for most smartphone OS's (android,windows,apple etc)
 
Probably about f/5.6. You just get to learn this stuff ;)

Go to the depth of field calculator here http://www.dofmaster.com/dofjs.html Input your camera model, which sets the size of the sensor (and is the bit you can't change) then play with focal length, f/number and shooting distance and all the answers will pop up on the right.

Unfortunately, DoF doesn't work on a linear scale but a curve that changes more strongly as the image gets bigger. Basically what happens is that DoF gets more shallow the closer you get, or the longer lens you use - both make the image on the sensor bigger. Though if you frame your group with a wide lens at close distance, then move back for the same framing with a longer lens, DoF will be the same (but persective and field of view will change how the background appears).

In practise, once you've got the image framed up the way you want from the right distance, you use the f/number to control DoF. Also on that site, you can create a custom rotary calculator to stick on your lens cap, covering up to three focal lengths. That will tell you what's what, but the advantage of that over the basic calcs you can download as a phone app, is you can instinctively see the relationship between distance and f/number and how things shift about.

Or you can buy a similar device called Expo Aperture for £30. It's a cool tool for learning too http://www.warehouseexpress.com/buy-expoaperture-2-depth-of-field-guide-2-disc-kit-metric-/p1523180

Edit: I'm slow today. DoF Master are doing good business :)
 
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Thanks all, these ate really good tips for me to go away and play now. I have downloaded the app which is great, gonna go and experiment now :-)
 
Just on this phone app thing, does anyone know of one that works like a rotary calculator? Along the lines of the DoF Master one that you print out, and reads like a conventional DoF scale as engaved on some lenses? I'd prefer that to a table of numbers that gives you no idea of what's happening either side of the actual number you've input.

I'm thinking iPhone type jobby where you touch the screen and the dial rotates. I've just done a quick google and nothing like that came up.

The problem with the printed out one on DoF Master is a) the limited range of focal lengths per calculator, and b) the range of distances covered. For example, if you have a 400mm lens, you want to know DoF for distant stuff, but if you also use it for small garden birds at 2m away, the scale won't go down that far with a long lens. A digital one could be easily configured to do loads of useful stuff like that. Macro too would be cool.

Any ideas chaps?
 
I have Phototools on android, not quite what you describe but it does allow you to set your own focal length favourites.. and I think you can set them by camera as well (so when you change between APS-C and 6x7MF the focal lengths change to match your kit bag). It displays the information I think you are looking for, but not in the conventional lens barrel display.. and you can drag the slider for the focus distance. As the information is there on the screen, I'm sure it's a matter of developing a GUI.. might be worth contacting the author.
 
Thanks Alastair. I can't be the first person to have though of this, DoF Master for a start. But I have no idea of the technology invloved, and presumably it's difficult. Much easier to create a table than an animated kind of device?

I guess it will happen if there's a will. Meanwhile, I need to get an iPhone first :D

Cheers :)
 
HoppyUK said:
Just on this phone app thing, does anyone know of one that works like a rotary calculator? Along the lines of the DoF Master one that you print out, and reads like a conventional DoF scale as engaved on some lenses? I'd prefer that to a table of numbers that gives you no idea of what's happening either side of the actual number you've input.

I'm thinking iPhone type jobby where you touch the screen and the dial rotates. I've just done a quick google and nothing like that came up.
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Mmm :thinking: not exactly like a lens readout but the one I use on my iPhone is called iDoF Calc and it is a spinny dially thingy lol. It works very smoothly and much quicker than DoF master, just a matter of taste really.

http://itunes.apple.com/us/app/idof-calc/id348599110?mt=8

Give it a bash its free
 
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