Problems with shallow dof images.. help please!

[Stacylouwho]

So I have my nifty fifty and have been using it a lot lately. I have noticed that sometimes I get really clear shots while using a shallow depth of field and others are not so clear. I was wondering if there are any rules I should follow when using a shallow depth of field? I have been shooting between 1.8 and 4. Subjects so far have been children but I have a few adult portraits coming up and wondering if there is any simple ways to fix this issue? Any help would be appreciated! I should also let you know these are low iso shots around 100 with a shutter of about 200-500.

 

[tirediron]

I wonder if perhaps a better understanding of DoF might not help you. First of all, have you ever used a DoF calculator? DoF is a physical property of the lens that is dependant on certain aspects of the your shot. First, long glass has inherently less DoF than shorter glass, as do larger apertures compared to smaller ones. The closer your camera is to the subject, the less DoF you will have and the larger your recording medium (sensor/film) is, the less the DoF will be. A moderate telephoto lens shot at a large aperture, close to the subject, (say an 85mm, f1.4 four feet away) might have a DoF as shallow as 1"!

 

[480sparky]

Aperture is only part of the equation. Other parts are camera-to-subject distance and how you've set your camera up to select and use it's focus points.

 

[Stacylouwho]

I wonder if perhaps a better understanding of DoF might not help you. First of all, have you ever used a DoF calculator? DoF is a physical property of the lens that is dependant on certain aspects of the your shot. First, long glass has inherently less DoF than shorter glass, as do larger apertures compared to smaller ones. The closer your camera is to the subject, the less DoF you will have and the larger your recording medium (sensor/film) is, the less the DoF will be. A moderate telephoto lens shot at a large aperture, close to the subject, (say an 85mm, f1.4 four feet away) might have a DoF as shallow as 1"!

I have been reading a ton, maybe too much it is all becoming a blur.. literally!! but maybe some of my shots were a bit too close given the dof. Thanks for your advice, I will read over it again. I have never used a calculator..

 

[480sparky]

I have been reading a ton, maybe too much it is all becoming a blur.. literally!! but maybe some of my shots were a bit too close given the dof. Thanks for your advice, I will read over it again. I have never used a calculator..

You can download this free program and play with it on your computer. Click on the focal length and choose the aperture, then you can 'focus the lens' to different distances and see where your DOF is.

 

[Stacylouwho]

You can download this free program and play with it on your computer. Click on the focal length and choose the aperture, then you can 'focus the lens' to different distances and see where your DOF is.[/QUOTE]

I will look into this thanks!

 

[kathyt]

Are you toggling your focus point or using BBF? How are you focusing?

 

[hirejn]

It sounds to me like you're struggling holding focus, which is common with such shallow DOF. Instead of wasting time with DOF calculators and freaking out over science, understand simply that at those apertures focusing requires greater precision. For example, if you focus on an eye at f/1.8 and either you or the subject moves a couple of inches, that could be enough to lose focus. Also, if you focus, and then hold focus but recompose slightly, that could also be enough to throw the image out of focus. The DOF is so shallow these small details matter. Moving kids? Not a great subject for f/1.8. A sitting portrait is difficult enough at 1.8. In addition, try single focus instead of continuous, which is always searching. Single focus enables you to lock on and stay in focus if you don't move. It's not the camera or lens not working. It's simply more challenging to hold focus at these wide apertures.The same principles apply to f/4 but the errors need to be more amplified to have an effect at f/4, or the shutter speed is too slow.

 

[cgipson1]

UH.. stop shooting wide open all the time? At least until you learn when you can get away with it? DOF can be very tiny... if you are too close, or pick the wrong focal point.

 

[Dao]

Another thing to watch out for shallow DoF is subject walk out from the focal point/plane. i.e. Camera AF set to one shot. Half press the shutter button to focus. And by the time you take the picture, the subject already slightly out of focus since it move away from the point where you have the camera focus set on.

 

[Stacylouwho]

Are you toggling your focus point or using BBF? How are you focusing?

I am choosing my point of focus and then taking the picture with the spot display is that the same as bbf? Thats how I usually take most all of my pictures.

 

[jowensphoto]

BBF = Back Button Focus. You use the same button as you do to zoom out when previewing pictures to focus while taking photos. It's awkward at first, but once you get used to it you'll never have go back to using the shutter release for focus.

 

[jake337]

Try using a tripod and live view. With my D90 I get my composition where I want it then move the focus point, in live view, to where I want it. I then zoom in on the eyes and adjust focus. I try not to "spray" but when shooting wide open it can sometimes be needed as the eyes may move out of the DOF just by breathing.


This video shows what I'm saying using the D5000. It shows how I do it with manual focus at around the 1:30 mark.

 

[cynicaster]

OP, I still recall the day I bought my nifty fifty; I picked it up on my way to a barbecue where I was looking forward to trying it out, in particular by taking some pics of my niece. Being a bit of a noob to DSLR at the time, and a total noob to that lens, I was pretty let down by the results.

Bottom line is that if you set that thing to f/1.8 and focus on a child a few feet away, you have ridiculously shallow depth of field, meaning very little room for error. You have a few things working against you, actually: kids never sit still, and the slightest movement between focus and shutter release can get you outside of your usable DoF; the lens is already not very sharp at f/1.8; the camera's autofocus system is far from perfect....

I'd recommend saving the really wide apertures for situations where your subject is willing to sit still. For the kid pics, stop down a bit, and watch your "keeper rate" markedly improve.

 

[jake337]

OP, I still recall the day I bought my nifty fifty; I picked it up on my way to a barbecue where I was looking forward to trying it out, in particular by taking some pics of my niece. Being a bit of a noob to DSLR at the time, and a total noob to that lens, I was pretty let down by the results.

Bottom line is that if you set that thing to f/1.8 and focus on a child a few feet away, you have ridiculously shallow depth of field, meaning very little room for error. You have a few things working against you, actually: kids never sit still, and the slightest movement between focus and shutter release can get you outside of your usable DoF; the lens is already not very sharp at f/1.8; the camera's autofocus system is far from perfect....

I'd recommend saving the really wide apertures for situations where your subject is willing to sit still. For the kid pics, stop down a bit, and watch your "keeper rate" markedly improve.

Yes, stopping down and choosing a background with a great distance from your subject helps.