Controlling Depth of Field

[sygyzy]

Many times I am shooting and while I appreciate shallow depth of field pictures for portraits or to isolate a subject, much of the time I want it to be a long DOF. I want everything to be in focus, in other words.

What is a general value range that would make everything focused? f/8? f/11?

Second, I have this dilemma I need help with. I use a 50mm f/1.8 prime to shoot mostly food or other objects. If I am indoors (not optimal lighting), and I want a wider DOF, I need to raise the aperture to say f/5.6+ The problem is when you raise the aperture, you are making the opening smaller (right?) and as a result, my shutter speed slows down and/or ISO raises. Well I can't exactly handhold a camera very well. The camera naturally wants to use the largest f-value (1.8) which means the cherry on top of my sundae will be sharp and everything else including the ice cream 2 cm below will be blurry.

What can I do?

Thanks.

 

[virtuamike]

Not just enough to set aperture. You need to take into consideration distance of subject to camera. The closer you're focusing, the less DOF you'll have. From there, look at distance of background to camera to figure out whether or not if falls into the DOF you have.

As far as shooting indoors, either get more light or deal with the restrictions that you'll have.

 

[fuzzybabybunny]

If you need there are DOF calculators:

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

It's impossible to give a good general aperture value that would make everything in focus. Like Mike said, depends on lens to subject distance, looking at the lens to background distance, subject to background distance (closer, easier to get within the DOF).

I could just tell you to shoot f/8, as this would be ok for a good number of your shots, but most definitely not all.

As for the indoors, get more light or get a tripod or both.

You can also try focus stacking with Helicon Focus or CombineZ

 

[ElFenix]

if you want everything in focus you need to set the hyperfocal distance on the lens. unfortunately a lot of current non-professional lenses don't have the markings for DoF on them, as that's the easiest way to do it.


at f/8 and focusing somewhere about 1/3 of the way to infinity will be close. f/11 would be better.

 

[andylawcc]

for 2) where the aperture is fixed at a small opening / large f value,
I crank up ISO, increase Shutter speed for longer exposure, and increase EV (exposure) too. A tripod will help to commensate shanky hands under long exposure.

 

[fuzzybabybunny]

Originally posted by: ElFenix
if you want everything in focus you need to set the hyperfocal distance on the lens. unfortunately a lot of current non-professional lenses don't have the markings for DoF on them, as that's the easiest way to do it.


at f/8 and focusing somewhere about 1/3 of the way to infinity will be close. f/11 would be better.

Hehe, 1/3 of the way to infinity would be.... infinity? I know what you mean, but it's just funny to think about.

 

[sygyzy]

Hi guys,

Thanks for all your help. I am still a noob at this so I have some followup questions and comments.

BTW, since I am usually shooting food at my apt before I dig into dinner or at a nice restaurant, I cannot exactly setup a tripod or adjust special studio lamps. That's why it's important for me to handhold.

Since it's a 50 mm prime and I want to just focus on the food, I cannot exactly move back. I have to get close enough for it to fit/fill the frame so that's usually about 2-3 feet.

I used FBB's online calculator with 50mm, Canon 40D, f/1.8 and 2.5 feet and it gave me results, but I don't know how to interpret them.

Subject distance 2.5 ft

Depth of field
Near limit 2.48 ft
Far limit 2.52 ft
Total 0.05 ft

In front of subject 0.02 ft (50%)
Behind subject 0.02 ft (50%)

Hyperfocal distance 242.4 ft
Circle of confusion 0.019 mm

It also says Depth of field extends from 121.2 ft to infinity. Does this mean I have to stand 121 feet behind the plate for everythign to be sharp? That's ridiculous.

 

[ElFenix]

what that says is that, at 2.5 feet distance, a 40D with a 50 mm f/1.8 lens has a depth of field of 1/20 of a foot, or somewhere near 2/3 of an inch. that's why not much is in focus.

 

[sygyzy]

What does hyperfocal distance mean?

 

[ElFenix]

hyperfocal distance is when you've focused on the distance that infinity has just come into focus for the given f-stop and focal length. at smaller apertures the hyperfocal distance is nearer to you. at f/11 or f/16 you can take long vista landscapes with practically everything in focus.

 

[sygyzy]

So are you saying that if the hyperfocal distance is say 10 feet for a given f-stop and focal lens, that if I focus on something 10 feet away, everything between myself and that object will be on focus? That only explains front focus. What about rear focus (objects behind the object? How focused will they be?

 

[ElFenix]

Originally posted by: sygyzy
So are you saying that if the hyperfocal distance is say 10 feet for a given f-stop and focal lens, that if I focus on something 10 feet away, everything between myself and that object will be on focus? That only explains front focus. What about rear focus (objects behind the object? How focused will they be?

if the hyperfocal distance is 10 feet for a given focal length and f-stop, then everything from probably 2 feet to infinity will be considered in focus. though at that f-stop you're probably decently into diffraction so not much will be sharp. given that you probably don't need focus on stuff 2 feet away (won't even be in the frame for a typical tripod shot), you should probably open the lens a stop.

 

[fuzzybabybunny]

Originally posted by: sygyzy
So are you saying that if the hyperfocal distance is say 10 feet for a given f-stop and focal lens, that if I focus on something 10 feet away, everything between myself and that object will be on focus? That only explains front focus. What about rear focus (objects behind the object? How focused will they be?

If hyperfocal distance is 10 feet, then everything from 5 feet to infinity will be in focus when you set the lens to focus at 10 feet.

If the lens is focused at hyperfocal distance H, then everything from H/2 to infinity will be in focus.

The above is the most common definition. There's another definition that muddies the waters a little bit but the above is good enough for practical use. You can further muddy the waters with things like circles of confusion but I wouldn't worry about it.

 

[LS21]

Originally posted by: sygyzy

BTW, since I am usually shooting food at my apt before I dig into dinner or at a nice restaurant, I cannot exactly setup a tripod or adjust special studio lamps. That's why it's important for me to handhold.

3 tricks:

-hold your breath to keep steadier
-if you can, prop camera/your arm against something (ie elbow on table)
-use a self timer- put camera on 2-second timer and snap the photo (this way your motion of pressing trigger wont affect camera movement during the shutter)