Depth of Field (DoF) and Hyperfocal Focussing

[suvarghyadutta]

Hello,

I am new to photography and would like to understand why the photos that i am capturing with my new DSLR (EOS 450D and Tamron 18-200 aspherical lens) appears to be fuzzy and blurred? I know camera shake is not the reason. I use a tripod and self timer.

I have read about hyperfocal focussing. Please refer to the DoF calculator in this website:
Online Depth of Field Calculator

Let's say, I am using the focal length of 20mm and aperture of F11. As per the calculator, the hyperfocal distance is 1.88 metres. The distance between me and the subject is say, 100 metres. So, what it means is that if I focus on a target which is 100 metres away from me, then I would get the DoF of 1.83 meter till infinity. Whereas if I manually adjust the focus ring at 1.88 meters then I would be getting a DoF of 0.94 meter to infinity.

I would like to understand two things. First, when my subject itself is 100 meters away, if I focus at 1.88 meters (hyperfocal distance) then would not the main subject itself be out of focus?

Second, if my lens doesnt have the hyperfocal distance chart drawn on it (Tamron 18-200 aspherical doesnt have it) then how do i manually set the focussing ring at the hyperfocal distance?

Please let me know if the questions I am asking are clear before you provide a solution. I will be grateful if some experienced user may please guide me and help me clear my concepts.

Also please see the following test shots that I have taken from my balcony:
Free File Hosting Made Simple - MediaFire

These photos cover two scenes ate various levels of exposure. The photos here are not cropped, but original uploads. Please don't judge them from the point of view of composition etc. The sole purpose is to understand why my images are lacking the sharpness. Camera shake is not an issue as these were taken on self timer on a tripod.

Regards.

[dcclark]

You seem to have things a bit confused:

If the hyperfocal distance is 1.88 meters, that means that you should focus at 1.88 meters. The result is that everything from 0.94 meters (which is 1.88/2) out to infinity will be in focus (including your subject). The fact that your subject is at 100m is irrelevant. Notice that, if you change 100m to 500m, or 3m, the Hyperfocal Distance field doesn't change. The entire point of hyperfocal distance, is that it's the distance which allows everything (from a certain distance outwards) to be in focus -- it ensures "maximum depth of field".

Next, while it's handy to have a hyperfocal distance scale, most modern lenses don't. The reason is that you need an aperture ring to properly figure this out -- and most modern lenses don't have that. However, if you use a calculator (or carry a chart, there are many available), then you can set your focus ring so that the correct hyperfocal distance appears in the window.

If your ring has no distance scale at all on it, then you're more or less out of luck. A handy technique in this case is to just focus "about 1/3 of the way into your scene" (something that can be hard to estimate). This approximates the hyperfocal distance, more or less.

To summarize: do not focus on your subject. Focus at the given hyperfocal distance (in this example, 1.88m), and your subject should be in focus as well as everything else out to infinity, and many things closer than that.

[suvarghyadutta]

Originally Posted by dcclark

To summarize: do not focus on your subject. Focus at the given hyperfocal distance (in this example, 1.88m)

Thank you very much for such a detailed and patient explanation. To understand better, the 1.88 meters point; is that the point that is physically 1.88 metres away from the spot where I am standing? Or does it mean than I would rotate the focussing ring on my camera to set the ring manually at the 1.88 mark on the distance chart of my lens (I know there is no such point as 1.88 m marked on the lens. I have 1m and then 2 m on the lens. So placing the pointer on the ring at a place slightly below the 2 m mark would approximate it to 1.88m)?

Also, if I place the focus at so near a spot, won't it affect the sharpness of the background distant subjects, than if I had focussed on the background subjects?

Could you please take a look at the photos I have uploaded (the link is the original question) and let me know where I have gone wrong with those photos in terms of lack of sharpness and blurry nature?

Regards.

[OsmosisStudios]

Originally Posted by suvarghyadutta

Thank you very much for such a detailed and patient explanation. To understand better, the 1.88 meters point; is that the point that is physically 1.88 metres away from the spot where I am standing? Or does it mean than I would rotate the focussing ring on my camera to set the ring manually at the 1.88 mark on the distance chart of my lens (I know there is no such point as 1.88 m marked on the lens. I have 1m and then 2 m on the lens. So placing the pointer on the ring at a place slightly below the 2 m mark would approximate it to 1.88m)?

These both do the same thing. If you point the camera at a spot that is 1.88 meters away, the focus indicator will be just short of 2m. The indicator on the camera shows what distance youre focused at.

[Sterling]

Also, if I place the focus at so near a spot, won't it affect the sharpness of the background distant subjects, than if I had focussed on the background subjects?

No. As dcclark said, if you focus at 1.88 meters then everything between 0.94 meters and infinity will be in focus. 100 meters is within this range so your subject will be sharp. It may look blurry in the viewfinder but that is because the viewfinder only shows the view at the lens' largest possible aperture (f/3.5?). If your camera has a depth of field preview button then you would see the full range of focus at your intended aperture of f/11. If no depth of field preview button, then you'll just have to take the shot to see that everything comes out nice and sharp.

[suvarghyadutta]

Originally Posted by Sterling

...If your camera has a depth of field preview button then you would see the full range of focus at your intended aperture of f/11...

My EOS 450D does have a DoF preview button, but the problem is that when I try to press that and change the aperture, the screen keeps getting darker and it is barely possible to make out what is in focus and what is not. Maybe it's something wrong with my eyesight, the viewfinder is also small, trying on live-view didn't help either; but I honestly am not able to tell any difference in DoF using the DoF button.

Regards.

[Sterling]

That's a normal issue with using the dof preview button. It stops down the aperture so the view can get pretty dark at small apertures. You will see the results clearly after you take the shot though.

[suvarghyadutta]

Originally Posted by Sterling

You will see the results clearly after you take the shot though.

The problem is that in the LCD pane all the photos looks very crisp and sharp. It's only after being downloaded on the PC that I find them not so sharp. By that time it might be too late to take another shot at that location.

[Sterling]

If you have followed the rules of using hyperfocal distance correctly then the lack of sharpness is caused by something else. I know you said you used a tripod but if it's a lightweight model and if it's windy, you could easily get some fuzziness from camera shake. Perhaps you could experiment with focusing in some non-critical locations to get a better idea of how hyperfocal distance operates.

[suvarghyadutta]

Originally Posted by Sterling

...tripod...if it's a lightweight model and if it's windy, you could easily get some fuzziness from camera shake.

I use a Camlink TP 2800 tripod and it was used inside my room. So in this case I may rule out the effect of wind. But you are right. I need to spend more time in photography before I can learn it properly. My only worry is that I should not be ending up with a faulty lens. I know only a bad workman quarrels with his tools, but then having spend quite some money on the lens, would love to ensure that got a correctly calibrated one.