Hyperfocal...DOF... eh, what? help.

[VibrantMindDance]

I've recently realized I never really consider focusing when i'm shooting. I mean, obviously I take in the DOF relation to aperture and adjust accordingly, but I never really think about where i'm focusing within the photograph.

So today I started going through my arsenal of photobooks... and i am confused. One book said when i'm looking for max DOF and sharpness to focus in the bottom third of the photograph... another book went into the whole hyperfocal distance, which i've no idea how to achieve on my usual setup (i shoot mostly wide angle landscapes with my sigma 10-20 on my canon 40D)...

Generally I keep my aperture around f/16 - f/22 for landscapes and adjust shutter accordingly... but I do find that my furthest sharpness does not compare to many the incredible photographs I see from others.

Any clarification on this subject would be great. I looked up DOF/Hyper focal distance/ etc on wikipedia, and it was a bit to... techie for me. The equations terrified me (i never got through algebra one in HS, numbers dont work for me).

Thanks all, you've been a great help in my learning process! This forum was probably the greatest learning tool i stumbled upon.

[digitaljohn]

That's a professional question. DOF is tricky and you need to practice. There is also some information on how far you stop down that is important. First for a normal shot the DOF lies one third in front of the subject and two thirds behind the subject. As you move in closer to a subject the DOF changes to 50% in front and 50% behind the subject. This is important if you want sharp and crisp focus in your image as the understanding of DOF allows you to open your lens. I have some very budget minded lenses which I do not recommend that anyone serious about photography should buy but I will tell you that when all is right the images can be amazing. Better glass will do a better job in most cases but my point is understanding what it takes to get a good technical shot will work with all lenses. I think others may have some points also so less start with point one

1. Always make sure the camera is rock solid. Any movement even from mirror slap can and will have a degrading effect on the image.

2. Always use a lens hood. Look at your lens and make sure it is in the shade of the lens hood. If not hold up a card and shade it. If you don't do this you could lose contrast and your image could turn muddy and dull.

3. This next one is going to get me into trouble but here it is. If you are
shooting digital never stop down any more then you need to after the first 2 or 3 f stops. With all lenses as you close down the light is diffracted by the side of the aperture as you stop down more you get more diffraction. With a view camera I used to shoot at f22 to f64 with only a slight degradation of the image but with digital after f8 or so (depends on the lens) the image degrades noticeably when compared to a wider open lens.
It's like taking a 14 mega pixel camera and getting a 4 mega pixel image.
The reason for this in digital is partly due to the less amount of light the sensor has to work with as well as the diffraction caused by stopping down.

Well that was a mouth full and I hope that I am not in to much hot water but please test and you will be amazed. If you are getting some good images and some no so good review the images and see what f stop was used you may be suprised.

[VibrantMindDance]

Ok. So I hear people speak about the lenses "sweet spot" often, what exactly and where exactly is it, and how exactly do I determine it for my lenses?

I never use the lens hoods. ever. They are probably still in plastic in the boxes. I always try to carry as little as possible since i'm hiking and climbing on dangerous cliffs trying to get a shot (that inevitably sucks anyway). I'll have to break out the hoods and use them. Do they have any other effect? Since my lens is so wide (10-20mm usually shot at 10mm) wouldnt their be significant vignetting?

Maybe the effect I'm seeing is also partially resulting from post processing... i'll throw some examples...

I've got so much more to learn. I should just take a class one of these days when i've got the money to spend.

There isnt even much depth in this shot, but the furthest rocks arent even sharp or focused... http://farm4.static.flickr.com/3146/2574587236_d31111cc6c.jpg?v=0

Then there is this shot by photographer Trevor Anderson, that has amazing sharpness so far back as well as right up close... THAT is what i crave... and he's using the same lens and body as me. http://farm4.static.flickr.com/3096/2549779581_b9df8a7f14.jpg?v=0


sorry about the links but i couldnt get photos to post.

[Bonish Photo]

Namaste, if your lenses come with hoods, never take them off. Especially if you're climbing around on rocks and hiking. I've saved the front glass on my lenses soooooo many times because of the hoods.

You should see how beat up my lens hoods are, this alone should tell you how much abuse they've saved the lenses.

It's going to be hard to get good DOF with such a wide angle lens. That is unless you're taking a Macro shot.

That image you posted a link to, it would be easy to take, just bracket a few different shots with different F-Stops till you get everything in focus.

[digitaljohn]

the hood that came with the lens will work. Hyper focal if you need and stop down if you must. Wide angle lenses do not degrade from stoping down as much as longer lenses. Sweet spot you will find after testing or just using a lens for a long time and looking at the images. As far a classes go they are OK but shooting is more important. Work on building your vision and composition and the camera will follow.

[bob_r]

Your link doesn't provide any exif data, but I suspect you may be setting your aperture at too small of a setting. I think by closing your aperture down so far, your images may be soft because of diffraction.

Here is a link to a hyperfocal calculator that might be helpful:
http://www.dofmaster.com/dofjs.html

Here's a link that explains diffraction.
http://www.cambridgeincolour.com/tutori ... graphy.htm

As for the sweet spot of your lens, photozone shows it at f/5.6 for 10mm and at f/8 for 14mm and 20mm. Your individual lens may vary from the one they tested, but I would try to stay within the the f/5.6 - f/11 range when shooting landscapes.

Hope this helps,
Bob R

[VibrantMindDance]

Thanks everyone. So i shall break out the lenshoods and use them. And I shall not use the smallest aperture possible in a failing attempt to achieve max DOF.

Smaller aperture... lens hood. I'll try, and I'm sure I will be back. I certainly do love this place! It's like free schooling. =)

Thanks Bob for those links. That DOF calculator is pretty awesome. I get a bit confused about the nearest focus area though because sometimes my lens is right on top of the foreground i want to be in focus. For example at 10mm with the subject 15 feet away it's saying that the "near limit" is 3.36 ft.
Also, that photo posted of Trevors was shot with the same lens and body i'm using, and it was shot at 10mm, f/18 for .3 seconds... as for my shot, i'm not sure but I can almost be certain it was f/22, 10mm and some "whatever" shutter speed. I think he's probably got some sweet post processing secrets as well. I'm not that CS3 savvy.

[diglloyd]

I've recently realized I never really consider focusing when i'm shooting. I mean, obviously I take in the DOF relation to aperture and adjust accordingly, but I never really think about where i'm focusing within the photograph.

So today I started going through my arsenal of photobooks... and i am confused. One book said when i'm looking for max DOF and sharpness to focus in the bottom third of the photograph... another book went into the whole hyperfocal distance, which i've no idea how to achieve on my usual setup (i shoot mostly wide angle landscapes with my sigma 10-20 on my canon 40D)...

Generally I keep my aperture around f/16 - f/22 for landscapes and adjust shutter accordingly... but I do find that my furthest sharpness does not compare to many the incredible photographs I see from others.

First depth of field is an illusion. It's a zone of increasing blur, with a very small zone of sharpness that exploits the sensor. Most DOF calculations equate to 0.5 megapixels for "sharp" based on 30 micron “circle of confusion”, a spot 25-30 times larger than the pixels on common digital cameras! Not sharp at all. Avoid f/22 at all costs, and f/16 will drop contrast to very poor levels.

If f/16 or f/22 is required for the image, make a different image; be clear about what matters in the image and focus there. The old 1/3 - 2/3 thing is not only technically wrong, it just doesn't work well. Focus on the most important subject matter. If that's unclear, compose a better image.

Digital cameras these days suffer hugely from stopping down too far, due to diffraction:
http://diglloyd.com/diglloyd/free/Diffr ... 1DsM3.html

WIth a 40D, you are degrading the image substantially by stopping down beyond f/11.

[diglloyd]

Thanks everyone. So i shall break out the lenshoods and use them. And I shall not use the smallest aperture possible in a failing attempt to achieve max DOF.

Smaller aperture... lens hood. I'll try, and I'm sure I will be back. I certainly do love this place! It's like free schooling. =)

Thanks Bob for those links. That DOF calculator is pretty awesome. I get a bit confused about the nearest focus area though because sometimes my lens is right on top of the foreground i want to be in focus. For example at 10mm with the subject 15 feet away it's saying that the "near limit" is 3.36 ft.
Also, that photo posted of Trevors was shot with the same lens and body i'm using, and it was shot at 10mm, f/18 for .3 seconds... as for my shot, i'm not sure but I can almost be certain it was f/22, 10mm and some "whatever" shutter speed. I think he's probably got some sweet post processing secrets as well. I'm not that CS3 savvy.

DOF calculators are a waste of time. f/22 is the very worst thing you can do to your image, it will be mush due to diffraction. Focus on what's key in the scene, and if you don't have that, make a stronger image. Shoot a bunch of images at f/2 or f/2.8, and make some strong images at those apertures first (shallow depth of field). After mastering that, very selectively stop down to the f/5.6 - f/11 range. That is enough for 95% of applications.

DOF won't make an image strong. But try Helicon Focus for as much DOF as you want. It's the only way to get high quality without degrading the whole image due to diffraction:
http://diglloyd.com/diglloyd/2009-02-bl ... liconFocus