Aperture issue

[anne07876]

Hi everyone -

I took this shot yesterday...and I often find that while one area of the subject - in this case the tap - is the feature, and if that subject isn't all at the same distance, often times one portion of the subject is less sharp than the other. So, in this case, the tap head is less sharp than the body.

I regularly do this, and would like to know from anyone here what is the best way to ensure that a subject such as this can all be in focus. As you can see, the tap's 'head' is less in focus than the mast.

The stats for this first sample photo are 56mm, F5.0, 1/100sec

http://img364.imageshack.us/img364/1...tails14lf9.jpg

I know that some might say that it would be a matter of changing the aperture setting, but I do have another photo here which is
56mm, F8, 1/50sec which I didn't choose simply because it looks more washed out. But, I see no difference in the actual focus area.
http://img519.imageshack.us/img519/6...ails199yv4.jpg

What would you have done? Am I asking the impossible?

Perhaps it is the angle?

Camera is a D300, if you need to know that.

Many thanks in advance

Annie

[lputman]

It might have to do with the focus points. Did you auto focus? Are you able to manually set your focus point? I don't have that type of camera, but I know that with mine, I can have it automatic or I can choose which focus point to use.

[anne07876]

Hi there -

The camera has a 51 point focusing system...

I am on the 21 point focusing system (you can choose). The camera was aperture priority, but I'm still surprised that only the back of the tap would be in focus.

[lputman]

I'm gonna go out a limb here, it could be because of the distance that you are from the item also, you are too close to your intended target. If you stepped back and took the photo again, you'd probably have the totally focused shot that you are referring to.

[PhotoNewt]

Originally Posted by anne07876

...and I often find that while one area of the subject - in this case the tap - is the feature, and if that subject isn't all at the same distance, often times one portion of the subject is less sharp than the other. So, in this case, the tap head is less sharp than the body.

This is actually the normal focusing behavior. When you (or the camera) sets the focus of a lens, only a narrow flat plane of the image will be in focus - this plane is always parallel to the sensor or film. All portions of your subject that are within this focal plane and parallel to the sensor will also be in focus.

Since the faucet in this image is not on the same focal plane as the body it will naturally be out of focus (more on that later).

...I know that some might say that it would be a matter of changing the aperture setting, but I do have another photo here which is
56mm, F8, 1/50sec which I didn't choose simply because it looks more washed out. But, I see no difference in the actual focus area...

I will dare to say IS an issue of aperture indeed - keep reading.

If you look closely enough at the fork and knive, you will notice on the second photo (f/8), is more clear and focused than the first. The reason for this is depth-of-field (DoF).

DoF is the area of acceptable sharpness that extends in front and behind the focal plane where an object will be perceived as sharp by the human eye. This depends on multiple variables such as sensor size, degree of magnification and how close you examine the print.

As a photographer you have control over how wide is your DoF; there are three things you should know that will affect the DoF on your photograph:

1. At a given subject to camera distance and focal length combination, a smaller aperture will increase DoF.

2. At a given subject to camera distance and aperture combination, a smaller focal length (wider angle) will increase DoF.

3. At a given focal length and aperture combination, a greater camera to subject distance will increase DoF.

Having said that, for the subject you are shooting, you may want to go back and take the shot this time with an aperture of f/16 (or f/22 if needed) and see how it looks. If this does not yield the desired result, use the other variables described above to get more DoF on the photograph.

You can also try focusing on the faucet not the body since DoF is usually distributed about 1/3 in front and 2/3 behind your focal plane - except for close up photography where it is about equal.

One last thought: all lenses have a minimum focus distance, if your subject is closer it will not be posible to get it in focus.

Hope this helps.

[anne07876]

Very helpful indeed!!

I no longer have access to that particular faucet, but will practice on my own faucet here at home and give you the results tomorrow (Saturday). Oh, this is very exciting now. Thank you so much again.

Stay tuned.

Annie

[anne07876]

Originally Posted by lputman

I'm gonna go out a limb here, it could be because of the distance that you are from the item also, you are too close to your intended target. If you stepped back and took the photo again, you'd probably have the totally focused shot that you are referring to.

I will bear this one in mind as well. Photonewt gave a pretty thorough explanation as well, and I'll be experimenting tomorrow with my own sink's tap and posting the shots tomorrow here. I'd do it today but I have too many things packed in already, but I really look forward to the exercise.

Thanks,
Annie

[lputman]

Definitely heed the words of PhotoNewt; he's helped me tremendously.

[anne07876]

Hi there -

these are the results of playing around with the focus points and aperture settings. I used a tripod in all cases.

Here is the first set all at ISO200, focus points on the back...

Image 1: (sink 25) is 18mm, F8, 1/4 sec
Image2: (sink 21) is 18mm, F16, 1 sec
Image 3: (sink 22) is 18mm, 22f, 2 sec

1:
http://img440.imageshack.us/img440/139/sink25hm3.jpg
2:
http://img524.imageshack.us/img524/1373/sink21ny0.jpg
3:
http://img529.imageshack.us/img529/3707/sink22ip1.jpg

Since I can only do up to 4 images at a time, I'll carry on in the next post....

[anne07876]

Here's the second lot:

The following images are from focusing on the front portion of the tap (the bit that is going downwards)

Image 4: (sink 26) is 18mm, F8, 1/3 sec
Image 5: (sink 27) is 18mm, F16, 1.3 sec
Image 6: (sink 28) is 18mm, F22, 2.5 sec

Image 4:
http://img56.imageshack.us/img56/5648/sink26qc8.jpg

image 5:
http://img56.imageshack.us/img56/2949/sink27pz8.jpg

Image 6:
http://img208.imageshack.us/img208/669/sink28iu7.jpg

Of the back focussing photos, the F16 one stands out as the most in focus.

However, on the front focus points (ie, I moved the focus area to the snout of the tap). Despite the focus now on the tap-head itself, F22 are once again the best but it really should be in all three regardless. It's the back of the tap that is meant to be changing. Hmmmm. I find this unusual and will be doing this exercise again later in the week with a variety of objects.)

Many thanks!