Aperture Priority/ Focus Modes

Hi all,

Im fairly new to photography but am aware of the basic principles (if there are any in this pass time!) but am just lacking a bit of practice.

I mostly take pictures of nature when im fishing (self takes with fish) and the usual types when on holiday, but both these are unpredictable and infrequent.

Im having issues achieving a blurred background affect when snapping my captures (I want the subject to be pin sharp). Now I understand I need to use Aperture priority to achieve this affect but Im guessing Aperture alone isnt always going to guarantee the desired result.

My Lens is the standard kit 18-55mm and only 'stops down' to f5.6. Been advised to buy a Prime Lens to achieve what I'm after, so this is my long term step in the right direction. Still, before I feel confident enough to invest I feel I have to gain a better understanding.

For example, I shot at f5.6 yesterday, had a large distance between me and the backdrop, yet the affect was pretty much non-existent. Only thing I can think of was that I wasn't as close to the camera as I could have been (Ive occasionally fluked the affect in auto mode when ive filled the frame well-this isnt easy when doing self takes though!)

What factors do I need to take in to consideration? What other settings could be contributing to poor results? The only thing I can think of is to keep away from the Dynamic modes of focus ad just stick to single point..but beyond that I've no idea.

Any help would be much appreciated.

Thanks

Rory

best to have a good distance behind your subject. Also large aperture 1.8 2.8 something in that range if possible. Other can explain better. Check out some DOF charts. Shoot a lot, and have fun. Ed

Here is a depth of field calculator.
Online Depth of Field Calculator
Practice around your home. Set up some potted plants or something and get a feel for how much background blur is possible with your lens and various distances.

Buy yourself a 35mm or 50mm F1.8 AF-S G lens will be a good start...Distance yourself from the background will help..

The concept that you need to understand, @Rawfocus, is depth of field.

To oversimplify, the larger the aperture (the smaller the ƒ-number) the shallower the depth of field will be, and the smaller the aperture (the larger the ƒ-number), the greater the depth of field will be.

Focal length also comes into play. At the same distance and ƒ-number, a longer lens will have shallower depth of field than a shorter lens.

The 18-55 zoom that came with your camera complicates things further by having an aperture that is not constant with focal length. At 18mm, the aperture ranges from ƒ3.5 to ƒ22, while at 55mm, it ranges from ƒ5.6 to ƒ36. Some quick calculations seem to indicate that the effect of focal length is greater than that of the changing aperture on this lens, that is, the depth of field is shallower at 55mm and ƒ5.6 than it is at 18mm and ƒ3.5.

Anyway, you're trying to get shallow depth of field. You want the subject to be in focus,and the background to be out of focus.

So, using that lens, you want the subject as close as reasonable to the camera, the background as far away as possible, the lens zoomed to as long a focal length as possible, and the aperture open as wide (as small an ƒ-number) as possible. You'll have to experiment with these parameters yourself, to learn how they relate and how to optimize them for a particular shot. You might even want to consider investing in a good, high-speed (large aperture) prime lens, if you're serious about pursuing tight depth-of-field shots.

Another principle you might want to investigate is bokeh.

pedroj said:

Buy yourself a 35mm or 50mm F1.8 AF-S G lens will be a good start...Distance yourself from the background will help..

Click to expand...

I am new as well and bought the 35mm mentioned above and it does amazing bokeh. I think it is pretty much unattainable with the 18mm-55mm kit lens. I was skeptical, until I bought it and found out for myself.

zoom lens mate 55-300 isnt that dear or a 1.8 35mm or 50mm very cheap and will give good bokeh , you dont need too shoot in aperture priority you just need a wide aperture , you can still get that shooting in any mode
i shoot aperture priority but if i want a fast shutter speed for shooting moving objects i just keep an eye on the shutter speed and adjutst aperture and iso too achieve the shutter speed i need even though im shooting in aperture priority , i dont need too change too shutter priority to do this

You don't need to go for the very expensive f1.4 lenses a 50mm f1/8 prime will give you the results you want when used at f1.8 or f2 in aperture priority mode you can adjust the exposure using the ISO if its too bright or too dark.
They will also give you a lot more detail of your fish!

Making the best use of the lens you own for this situation, you want to use its largest aperture at the 55mm end. That means the aperture will be f/5.6. There is a physical difference in the diameter of the aperture when comparing it at 18mm vs. 55mm, and the diameter of the aperture affects DOF (especially when used in conjunction of being close to the subject and having distance between the subject and its background).

So get as close to your subject as possible while distancing the subject from the background as possible, and shoot at f/5.6.

EDIT: Let me add that when I say get as close to your subject as possible, that doesn't mean at the closest focusing distance. You don't want to create distortion so you want to be close enough without distorting the features of your subject.

egosbar said:

zoom lens mate 55-300 isnt that dear or a 1.8 35mm or 50mm very cheap and will give good bokeh , you dont need too shoot in aperture priority you just need a wide aperture , you can still get that shooting in any mode
i shoot aperture priority but if i want a fast shutter speed for shooting moving objects i just keep an eye on the shutter speed and adjutst aperture and iso too achieve the shutter speed i need even though im shooting in aperture priority , I dont need too change too shutter priority to do this

Click to expand...

Good point. Sometimes there is a lot of back and forth discussion on whether someone should shoot in aperture or shutter priority for a given situation. It really doesn't matter as long as you understand the relationship between the two and keep an eye on what is important to you. It is more of a convenience feature that we can lock one or the other by choosing aperture or shutter priority.

For that blurred back ground get a fast prime. The 50mm F1.8G and the 35mm F1.8G DX are amongst the least expensive lenses you can get. The longer the distance between the camera and the subject the larger the DOF, so as recommended, get as close as possible.

Hope this is what you want


or

can get sigma lens also as now they had cash rebate