Depth of Field.. Help!!!

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lemonsprig

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Name
Ian
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Hey All,

I need a bit of help.. I have recently joined the forum and have read through CT's excellent tutorial on aperture and shutter speed. So tonight I thought id try to work out what all the dials on my camera do.

In particular I was experimenting with depth of field, and having seen some excellent pictures in the past of pencils and the like where one is pin sharp and the others blurred I thought id give it a go.. Sadly no pencils, so I set up some vegetables and thought well if i can blur some of them or at least the background it will prove the point and I can see how it works..

well several shots later, small aperture, big aperture, macro mode with both big and small and err my results.. hmmm less than impressive.. To be honest hardly any burring if any.

But take a look and please please please tell me what I am doing wrong. I hope if you right click it you can see the data about aperture etc.

ISelby-2011-10-31-4.jpg


ISelby-2011-10-31-3.jpg


ISelby-2011-10-31-1.jpg


ISelby-2011-10-31-2.jpg
 
What camera/lens are you using?

Your reference ot macro mode suggests a compact camera - and due to the size of the sensor and the short focal lengths it is much harder to get much reduction in depth of field on them.

Edit, I can see you are using a powershot SX40. Try framing the same shot but at full zoom with the widest aperture. The focal length makes a difference you see.
 
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Hi Richard,

I am actually using a SX40 HS, although that is not a true DSLR not sure it quite qualifies as a compact either :)
 
Hi Ian

I think your problem is you have all the veg bunched together, space them out 8-10 inches apart along the counter, largest at the rear, smallest at the front.

Then position yourself at one end of the line and try again, I think you will get the results you are after.


John
 
Hi John,

I will give that a go, but shouldnt it at least have blurred the background tiles?

I have seen some amazing photos of flowers and stuff, where the head is pin sharp but leaves and twigs close by are nicely blurred.
 
well according to the canon site some tech specs are as follows

Type
12.1 Megapixels 1/2.3-inch CMOS sensor

Total Pixels
Approx. 12.8 Megapixels

Effective Pixels
Approx. 12.1 Megapixels

Lens
Focal Length
4.3 (W) - 150.5mm (T) (35mm film equivalent: 24 (W) - 840mm (T))

Digital Zoom
Approx. 4.0x, up to 140x in combination with optical zoom

Focusing Range
Auto: 0 in. (0 cm) - infinity (W), 4.6 ft. - infinity (T)

Normal: 2 in. (5 cm) - infinity (W), 4.6 ft. (1.4 m) - infinity (T)

Macro: 0 in. (0 cm) -1.6 ft. (50 cm) (W)

Autofocus System
TTL Autofocus, Manual focus*

* Shooting standby only in movie mode
 
So that's approximately 1/6th the size of a full frame DSLR. I had a look as well and, as far as I can see, the max aperture is f2.7 but on a sensor that small, that's probably equivalent to about f8 to f10 on a camera that can produce the kind of DoF you're looking for. Can't see how it's going to happen at that smaller aperture.
 
oh no :( please dont say that.. I only just bought this camera and that was one style of photo (close up macro with nicely blurred elements) I was really hoping to be able to take, I thought with a 0mm focus macro mode that would be possible...

Gahhh, I totally need to not seem depressed and let the missus in on this she hates, cameras, photos as it is.. if she realises i botched the purchas.... oh dear.
 
lemonsprig said:
oh no :( please dont say that.. I only just bought this camera and that was one style of photo (close up macro with nicely blurred elements) I was really hoping to be able to take, I thought with a 0mm focus macro mode that would be possible...

Gahhh, I totally need to not seem depressed and let the missus in on this she hates, cameras, photos as it is.. if she realises i botched the purchas.... oh dear.
Click to expand...

I may be wrong Ian, as I don't know your specific camera. I'm just going on the technical side as far as sensor size and aperture are concerned.

Hopefully someone else will come along who can help you further.
 
Fabs is correct. One effect of a small sensor is that the depth of field will, in general, be large.

However, if you are taking macro photos the depth of field will be smaller.

For normal (ie non-macro) shots you can get a smaller depth of field by getting further away from your subject, zooming in and using a large aperture. You'll need to be careful about keeping the camera steady, but it is a possibility.

Dave
 
Try it at full zoom and max aperture as I suggested - you might be suprised.

It won't be as good as a DSLR but at full zoom and as close as you can focus is where you will get the narrowest depth of field.

Unfortunatly as has been mentioned already, depth of field control really isn't the strong point of almost any compact camera.
 
You can do it, but you'll have to use small subjects so you can get in REALLY close. For example:

ebay094.jpg


(That's f1.8 though and it's still massive DOF)
 
thanks all, I have tried standing as far back as i can and using zoom and large aperture but am not getting much better results, or the camera is struggling to focus. Possibly the poor light and fact i cant get much distance.

I will try some more tomorrow over the weekend, but I may have to resign myself to the fact that im not going to be able to get these types of shots with this camera, sort of annoying as with the dark nights and we weather I thought I could at least practice this type of stuff at home.. Oh well you live and learn.

just one more question though in relation to macro, I thought that one of the key elements to a good macro shot was the blurred backgrounds etc, now according to the specs reviews i read this camera was great for macro shots, can focus really close etc. doesnt that defeat the purpose, or am I just missing the point, what sorts of macro shots would work with this.. (yes I am clutching at straws here, looking for a positive at least :) ) any examples and inspiration would be good :)
 
doh, should have refreshed before posting I was down stairs trying some of the suggestions.

I see what you mean Alan..

Anyone got any more inspirational examples :)
 
lemonsprig said:
Hi Richard,

I am actually using a SX40 HS, although that is not a true DSLR not sure it quite qualifies as a compact either :)
Click to expand...

Sorry to say it is a 'compact' but with a big range lens on it. In fact the sensor is on the small side of average for a compact (which helps to get you that big zoom range) with a crop factor of 5.6x, which means the sensor is actually less than 1/30th of the area of a full-frame digital sensor. It's tiny.

In terms of depth of field, you need to multiply whatever f/number you're using by 5.6x to get the equivalent DoF in full frame terms, ie f/2.7 becomes an effective f/15.1 for DoF calculations. You can work it all out here http://www.dofmaster.com/dofjs.html and if you input your camera model in the top-left box it will do that conversion for you.

Bottom line though is, if you want shallow depth of field and nice blurry backgrounds, you need a camera with a much bigger sensor :(
 
With smaller items you can do pretty well. Here is a shot of my watch taken last year on my SX1 at max focal length and aperture as wide as possible (f5.7). The bottle in the background is about 12" back so you can get an idea of how much you can blur the background.

I used manual focus set as close to the camera as possible then by moving backwards and forwards slightly I could see when I reached the optimum point to take the shot. Much better than relying on the AF.

macro.jpg


One problem that always happens when using a narrow field of view and can be seen here is the watch looks distorted. Can't be helped though if you want to get this sort of shot.
 
lemonsprig said:
Hey All,

I need a bit of help..
Click to expand...

Use the widest aperture you can and experiment with different zoom lengths. You'll probably find that you'll get the shallowest DoF at the longest zoom + widest aperture, plus also focus as close as you can. Once you've done that you've done all you can.
 
It IS possible on a compact. Here's a shot taken on a Canon Powershot 1100is. Technically it should have a very wide DoF, as it has a tiny sensor, was taken at the shortest focal length, and at f8, but in macro mode.

I think the key with compacts is to have the background objects some way behind the subject, which in turn is close to the camera. In other words, accept that the DoF is wide, and place the objects you want to blur outside it.


Untitled by MarkBerry1963, on Flickr
 
Thanks everyone, I guess its just going to take a bit of practice to really understand the limitations of whats possible or not.

And maybe come up with some other subjectst than close up to practice with.

@Mark1616, @Southdowns - your images do give me a glimmer of hope that I can achieve these types of shots, although the distances may mean that its not so suited for setups on my kitchen counter.

Again thanks all, and at least I can say I have learnt that 'Size is Important!!'
 
Just to prove it can be done: F2 on a 1/1.8" sensor, focussing is set at 30mm from camera, IE frigging close!

pencils008.jpg


Note the DOF is only 2-3mm.

Now focussed some 40-50mm away, the DOF has increased to around 10mm already:

pencils002.jpg


You'll have to focus manually for this kind of shot though, it's very unlikely the camera can read your mind as to where the DOF band should go.

Keep trying - you'll never get it with begetables, but as shown above, you can get it with some stuff easy enough. :thumbs:
 
Alan Clogwyn said:
Just to prove it can be done: F2 on a 1/1.8" sensor, focussing is set at 30mm from camera, IE frigging close!

Note the DOF is only 2-3mm.

Now focussed some 40-50mm away, the DOF has increased to around 10mm already:

You'll have to focus manually for this kind of shot though, it's very unlikely the camera can read your mind as to where the DOF band should go.

Keep trying - you'll never get it with begetables, but as shown above, you can get it with some stuff easy enough. :thumbs:
Click to expand...

You are in a very fortunate position here as that sensor is larger than the SX40's also you have a much wider aperture to play with which helps.
 
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lemonsprig said:
Thanks Mark & Alan.

I will keep trying, and now that I am aware that it will be difficulties, I know not to let it get to me when I dont get anything close to what I am trying to achieve.

Guess I was sort of inspired by shots like these (hope its ok to link to shots that i saw popping up in the random images on the side of the forum)
Click to expand...

Best to just link rather than embed. ;)
 
Sorry fabs I just copied it from the box when i viewd the image.. for future reference do I just remove the img tags
 
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