Hyperfocus & DOF Question

Morning Folks!!

My trusty tripod stays in my little commuter's trunk all the time, but sometimes it's just not feasible/practical to take it out, and sometimes I just don't have it with me if we're in the family car, or whatever. Being an amateur, it seems I usually don't have it more than I do

I try to go hyperfocal with my landscapes for obvious reasons, and with the spring rains here in KY, I have come across quite a few vertorama opportunities which I have availed. A lot of times I just pull off to the side of the road, and shoot

From the charts below, I can see that I can get infinite DOF at F6.4 on my 5D2/24-70 (my main kit). So other than difference between the distance in-focus in front of the subject, I get the same results at F6.3 - F16+. This couple of feet distance in front of subject is negligible; so when would I ever need to use F16?

Other than to expose properly in bright light (for which I can use shutter speed also), or to get starbursts, does F16 offer any benefits over F6.3? Do you not start getting fuzzy at F16+ as well? If anything, F6.3 allows me to shoot handheld far longer than F16, which is why I am asking this question as well. I also try to expose a third to the right, so the F6.3 works better for handheld dawn/dusk shoots.

Please see my FB page in my signature for samples of my work. My whole life and hobby is a work in progress; any thoughts, ideas would be greatly appreciated

Have a great weekend!!!!

Well, you have to consider the fuzzy nature of DOF tables and the fact that being "within the DOF" is not the same as "in focus" or "sharp".

Firstly, DOF tables take all sorts of things for granted. Not least is that you will be viewing a standard sized print at a standard distance (something like a 10x8 at arms length). If you make a bigger enlargement, you will get less DOF, if you crop the image, less DOF, view it closer, less DOF. Have better eyesight than the tables allow for, or have a different concept of what is "acceptable" sharpness, you again get less DOF. If any of these may apply, then you want to use a smaller aperture, maybe not as small as f/16 but not the basic aperture suggested by the DOF table.

There is also the fact that the DOF zone is simply what is deemed to be "acceptably sharp". Your image is only truly sharp at the distance you focus on, from there outwards in each direction it will get gradually softer until it reaches a point where it is considered that the softness is "unacceptable". As I said above, that differs from person to person. If you are a pixel peeper, you won't get remotely close to the DOF you see in the tables. You will see a lot more softness and a much shallower DOF at f/6.3 than you will at f/16 (or possibly f/11, as f/16 may start to introduce some diffraction softness). The same goes if you are making bigger prints, I enter contests and exhibitions and need bigger prints for that, so the DOF given in the tables is not nearly deep enough for me, as the softness will be unacceptable well within the distances quoted (particularly as judges tend to look closely as well).

Shooting hyperfocal distance will tend to give you a soft horizon, even though it is within the DOF. So, it isn't always a good idea to always focus on the HFD. I prefer to focus on whatever is nearest that I want sharp and then sort out the aperture to give me maximum sharpness over the rest of the image I want within the DOF. So, if I have an item of interest at 25 feet away, I will focus on that and not at the HFD of say 10 feet. I will then shoot at a smaller aperture to bring the DOF as close as I can. This ensures that the sharpest part of the scene is the subject, and not some random bit of grass that happens to be at the HFD. This will also make the far distance sharper as the horizon is now well within the DOF, rather than on the edge and so borderline "unacceptable"

You can still get your DOF to cover the area you want, but because you are focusing further back you need a smaller aperture. So, to answer your question, you may need f/16 to allow you to focus on the main point of interest, and still have your DOF cover 5 feet to infinity. You may also want f/16 to maximise the sharpness of your foreground and horizon.

DOF tables are only a very rough guideline. You need to factor in what you want and need from the final image and shoot for that, not to an arbitrary number on a table.

Ah yes, I mistook HFD = infinite DOF to also mean HFD = infinite DOF + tack sharp front to back. Like you said, 'Acceptable Sharpness' is all relative.

I'll try 16 down to 11 and see if I can tell a difference, and then try to stick with it.

Thanks for taking the time to explain

One thing not considered too by the tables is when people crop. That results in a larger magnification so "standard print size" doesn't apply anymore.

Also note the near limit of your DOF. Any aperture can have the far limit at infinity, using a smaller aperture allows you to capture a closer near limit while maintaining that far limit of infinity. Landscapes shot with a wide angle lens (including 24mm) often lend themselves very well to being low to the ground. If your near limit is 5 feet, your foreground is going to be out of focus. Of course, this isn't a rule but I know I find myself kneeling behind my tripod a lot.

Also as mentioned above, "within DOF" and "acceptable focus" do not mean critically sharp - you'll notice it right away in a large print and under scrutiny in small prints and you'll be disappointed if you're expecting your hyperfocal near limit to be razor sharp.

Of course, stopping down to f/16+ may not be the answer either due to diffraction or the need for stopping motion/keeping ISO in check (waves, wind, clouds, etc). This is where tilt on a T/S can help depending on the scene and why focus stacking is no longer just for macro shooters.

I would suggest using HFD as your baseline using your distance scale/aperture/infinit​y marks on the lens and then using the DOF preview button and live view 10x zoom to make sure all key elements are in focus - foreground interest to horizon. (remember to hold the DOF preview button down while in live view to see the affect of the aperture - if you don't, you're seeing what the focus would look like if your lens were wide open) If you find yourself at f16 and you still don't see what you want, you'll have to consider focus stacking.

Ahh! A T/S .. I've been thinking about one for sometime; especially after reading about the Canon 17mm being the sharpest lens EVER, and that a lot of pro landscapers use it! Would anyone care to argue that statement?

It would help so much if they wern't so expensive though; alas, my amateur status does not allow me $2400 for a highly specialized T/S landscape lens

Last time I thought about a T/S, I decided to rent one for a long weekend and see if I could get some results from it. The one thing that bothers me though is that I have never even held a T/S in my hands and I have read that using/mastering them (especially for landscaping) is a little tricky; so I wanted to read up on the usage/process a little before I actually rented one so I don't spend half my time trying to bend it properly Any info in this area would be greatly appreciated as well.

AFA focus stacking is concerned, I know as much about it as I know about T/S-ing. I infer it means using your focus points to take multiple pictures and then to merge them in PS. The one thing that troubles me is how one could grab the camera, change the focus point, shoot, repeat, without shaking the pic up a bit, and also, clouds and waves would have big time movement in them, right? Is there a special merge application that helps with this?

Freddy ..

alphamalex wrote in post #16914729
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AFA focus stacking is concerned, I know as much about it as I know about T/S-ing. I infer it means using your focus points to take multiple pictures and then to merge them in PS. The one thing that troubles me is how one could grab the camera, change the focus point, shoot, repeat, without shaking the pic up a bit, and also, clouds and waves would have big time movement in them, right? Is there a special merge application that helps with this?

Freddy ..

I use CombineZP which handles the issues like merging your photos. It works well for me.

alphamalex wrote in post #16909362
Ah yes, I mistook HFD = infinite DOF to also mean HFD = infinite DOF + tack sharp front to back. Like you said, 'Acceptable Sharpness' is all relative.

I'll try 16 down to 11 and see if I can tell a difference, and then try to stick with it.

Thanks for taking the time to explain

He's correct. You don't want to treat this like a mathematical formula that gives you discrete results. It's a feel to the image that you're going for. Maybe f/22 will give you a better result than f/16. You have to know what's going on and experiment with different looks to know what you want. Just because f/22 is a little soft doesn't mean you should avoid it... The softness yet more uniform focus might actually work better for the image. Don't avoid it just because a DXO test tells you it's not an optimum sharpness aperture size.

The version 1 of the 24-70 you're using is a little soft to begin with anyway, so play with that.