Here is David's question:
"My aim is to use the 18-55mm kit lens with the
majority of shots taken at the widest end. I have in mind setting the
lens at Hyperfocal distances, based on a crop factor of 1.5 and a circle of
confusion of 0.02. I think the first figure is reliable, but I'm not sure about
the second in relation to the X-E1 - perhaps you could confirm.
I have already done some testing at home using the
attached table (which come from the well respected DOFmaster site).
In my experiment I carefully measured distances at apertures
of f8 and f11 using a tripod and a printed card as the subject. I set the
lens manually at the hyperfocal distance, using the EVF distance scale. I was
disappointed to find that the closest point of focus was not as sharp as I had
hoped. Have you any idea why this may be?
I did a further test on aperture f11 and this time set
the distance scale at 4 feet (2/3 of the way between 3 and 5 feet). This
resulted in a sharp image from 3.5 feet. This would suggest that the
distance scale is not accurate.
Any suggestions you have to overcome the problem would
be much appreciated."
For anyone who might not know what it is, the hyperfocal distance is the focus distance point in a scene that will achieve the maximum over-all focus for the scene at a given lens aperture for the particular lens you are using. The key word here is "maximum". This is not saying that "everything" will be in focus. There is a big difference. Much of the ultimate focus results will depend upon -- and differ -- with the focal length and aperture you use.
A problem shooting digital lenses is that they do not perform at their best when stopped way down into the f/16 and small range. It is much better in terms of resolution to use the lens at its sweet-spot of around f/5.6 or f/8. This makes achieving a complete focus from foreground to background very difficult.
I prefer to use work-around solutions to achieve the same effect.
First, you can use a tilt-shift mechanism with a Nikon lens on the Fuji X. There is one available for the Fuji XF mount. I discussed in a previous blog post here. (You can purchase it here on Amazon.) Of course, this presupposes you have a Nikon lens of the desired focal length available. Not the most practical solution.
Actually, hyperfocal distance, or what I will call "aparent hyperfocal distance" is dependent more on the level of sharpness we consider to be acceptable. This brings me to the second work-around, which is the most practical:
Rather than simply try to get everything in focus, try narrowing your own mental focus about what is important in the scene and achieve a primary focus on that allowing the rest of the scene to go a bit softer. This is the method I, and many other landscape photographers, often use. It works well on several accounts. First, it forces you to make a decision on what is important in the scene and zero in on it. Second, it allows you to place the focus point closer to the foreground where you can achieve complete foreground focus of the elements in the scene that most benefit from sharp focus. Finally, you are allowing the background scene to go slightly soft, but that is the area with the least actual detail anyway. Plus its softness may not even be noticeable because of the magicians slight-of-and trick to distract your audience into looking at the foreground detail. Let's look at a couple of samples below.
If you are really determined to achieve a photo with everything in focus, then you might want to consider this third, alternative approach of a stacked-focus image. To do this, you take a series of photographs while moving the focus point slightly backward with each exposure until you have covered the entire area from front to back. Later the images are assembled with a program like Helicon Focus into a final image where the entire scene is in focus. The final results can be a mind-blowing experience for viewers because we rarely see real life this sharp. The image below is an example of stacked focus.
Bottom line here is that it more important for the photographer to come to a decision about what is the most important element in a scene and then judiciously relate that area to the whole by using depth-of-field, as opposed to randomly selecting a hyperfocal distance that bears no meaning in and of itself other than achieving a deep focus. As always, it is the photographers aesthetic decisions that are most important in any photograph.
Actually, hyperfocal distance, or what I will call "aparent hyperfocal distance" is dependent more on the level of sharpness we consider to be acceptable. This brings me to the second work-around, which is the most practical:
Rather than simply try to get everything in focus, try narrowing your own mental focus about what is important in the scene and achieve a primary focus on that allowing the rest of the scene to go a bit softer. This is the method I, and many other landscape photographers, often use. It works well on several accounts. First, it forces you to make a decision on what is important in the scene and zero in on it. Second, it allows you to place the focus point closer to the foreground where you can achieve complete foreground focus of the elements in the scene that most benefit from sharp focus. Finally, you are allowing the background scene to go slightly soft, but that is the area with the least actual detail anyway. Plus its softness may not even be noticeable because of the magicians slight-of-and trick to distract your audience into looking at the foreground detail. Let's look at a couple of samples below.
If you are really determined to achieve a photo with everything in focus, then you might want to consider this third, alternative approach of a stacked-focus image. To do this, you take a series of photographs while moving the focus point slightly backward with each exposure until you have covered the entire area from front to back. Later the images are assembled with a program like Helicon Focus into a final image where the entire scene is in focus. The final results can be a mind-blowing experience for viewers because we rarely see real life this sharp. The image below is an example of stacked focus.
Over twenty photos were taken to form this image. Each exposure was focused at a slightly different point moving progressively from front to back. All were later assembled to form on over-all sharp image. Click here to download a high res version of this photo. |
From your experience what is the difference between stack focus and aperture set for e.g. 22?
ReplyDeleteStack focus will produce sharper results over all. Working at small apertures like f/22 is not desirable. Digital sensors are not like film and the images degrade as the aperture closes down much past its sweet spot of around f/8.
ReplyDeleteI worked with analog very long but after switch to digital I noticed that the annoying problem is dust which comes to life after f10 ... quality of closed aperture is not that big issue for me but I work still with 30D which is old equipment ...
ReplyDeleteHi Tom - love your focus stacked image above, plus the focus stacked wine and cheese studio shot you did earlier. How do you figure out how many images are needed in the stack and how much to move the focus between subsequent exposures? Do you simply focus on the closest point first and then manually move the focus by a fraction at a time to cover the range? I'd like to use this more outdoors, so would like to come up with something that would work fluidly fir me. Many, many thanks in advance for your thoughts and advice.
ReplyDeleteHi Tom - love your focus stacked image above, plus the focus stacked wine and cheese studio shot you did earlier. How do you figure out how many images are needed in the stack and how much to move the focus between subsequent exposures? Do you simply focus on the closest point first and then manually move the focus by a fraction at a time to cover the range? I'd like to use this more outdoors, so would like to come up with something that would work fluidly fir me. Many, many thanks in advance for your thoughts and advice.
ReplyDeleteIt's taken a lot of trial and error, but generally I find that working around f/5.6 is best. I then move the focus manually in very tiny increments from the closest point where I want focus to the furthest point. For still life where the overall subject is a short distance I have someone insert a ruler so I can pinpoint the focus increment exactly. With a large scenic it's mostly guesswork and a very steady hand. You might find that accuracy is improved by using a more exacting video rig for pulling focus on your camera.
ReplyDelete