How To Use Auto-Focus to Nail the Focus Every Time! And WTF is Image Separation?
IntroductionThis is an edited response that I posted in a thread regarding focus and image separation and I'm re-posting it in its own thread here in hopes that it can help people who are trying to hit the next plateau with their work. Much of it is made up of my own opinions and I hope it becomes the starting point for a discussion within the thread, where others can add their own opinions, ideas and experiences, with the intention of helping people improve their work. If people want to post images here and ask for help troubleshooting issues or for advice from the more advanced shooters in the community on how to make improvements, that would be great, as well.
I think this group is great in that it allows us all to post some of our work and get positive feedback quickly. I don't know that the group has been exploited to the point where constructive criticism, suggestions for improvement or knowledge/instruction are freely shared. I'm not a professional, but I see a lot of posted work that could be easily improved with a few simple tips, but I'm never comfortable sharing my opinions for fear of offending the poster. So, instead, I'll offer this to see if it's something that the community finds helpful, and if so, I'll make similar posts in the future as I have time. I do this expecting feedback that would help not only beginners and casual photographers, but also help me grow and become better, as well.
I didn't go into deep detail on any concepts here but would be happy to if anyone has specific questions. I know there are other high level photographers in here who would be happy to help as well.
Where to Focus
For any animal or people shots, it's best to focus on the nearest eye of your subject because that is where you want the viewer's attention to be focused immediately. It's certainly possible that the subject of your portrait is a different part of the body, of course. For example, you've seen the typical wedding portrait of the couple, with the bride's hand extended in front of her and the focus is on the wedding ring and the couple are slightly out of focus so that your attention is drawn instantly to the diamond. But, for most people and animal portraits, the nearest eye will be your focus target.
For other types of fine art, landscape or action photography, the focal point will always be where you want the viewer's attention drawn first. So, it's important to know how to make that the focal point of the image.
Get Off of Default AF Area Mode...NOW!
If you're using the default auto-focus (AF) area mode of your camera, you're letting the camera decide where your focal point is going to be in your images...and the camera never gets it right. For informal snapshots, especially when using wider-angle kit zoom lenses with small maximum apertures yielding a lot of depth of field (DoF), this isn't a big issue. But if you're doing serious fine art, portraiture or wildlife work and you're using wide open apertures to blur out your backgrounds, which decreases your DoF, you need to have your focal plane dead on or your subject will be out of focus.
On some newer mirrorless cameras there's an AF area mode for eye detection, including detecting animals' eyes, and focusing on them...this is an invaluable feature as it allows for worry-free composition. On DSLRs and older mirrorless bodies, the best solution (and it's what I do) is to use single point AF area mode, where there is just one point in the view finder (VF) that the camera will focus within, and you put that little square point in the frame where you want your subject's nearest eye to be (it's an extra step but well worth the effort). Then, looking thru the VF, you lay that little square over your subject's nearest eye, acquire focus and snap. Obviously, this is more challenging with moving targets, like birds in flight, and there are more suitable AF area modes for that.
For all other types of photography with a static subject, single point AF area mode is the only way to go. You want to select your focus point...the camera can't read your mind and know exactly where you want the focal point to be.
Also, I set up my camera to use back button focus instead of doing the half-shutter-press and I set my AF to continuous (as long as I am depressing the back button, the camera is tracking the focus)...I find this to be more helpful in acquiring and locking focus. When shooting animals or people, I'm looking to get this kind of focus on the eye(s):
Worth noting: Even most of the older mirrorless cameras at least have eye detection AF for people (if not for animals) and it is an invaluable tool for shooting portraits or people in the streets...It allows you to compose as you wish and the camera will find the eyes of your subject and lock in focus on them no matter where they are in the frame. I shot this lovely model with my Lumix G9 using eye detection AF area mode:
Image Separation and Depth of Field
You've all seen photos where it looks like a tree branch or telephone pole is growing out a person's head or where there is a massive tangle of distracting branches right behind a squirrel in a tree, making it hard to even see the squirrel. Blurring out distracting backgrounds, while ensuring that your subject is razor sharp, to allow that subject to really pop (separating your subject from its surroundings), is important. You do this by decreasing your DoF (the range in front of and behind your subject that is in reasonable focus) as much as possible. Without a large range of DoF to mask the fact that you might have missed the focus on your subject, pin-pointing the focus becomes even more important. Once you're comfortable with single point AF area mode, you'll be ready to enhance your photos with image separation.
When you use prime lenses with larger maximum apertures, you're going to have more control with image separation, but even if you're using consumer grade or kit zooms, you can still turn your backgrounds to butter by using the proper settings and positioning yourself correctly in relation to your subject and the background. First of all, when shooting something like birds, shoot wide open (largest aperture on the lens, which is actually the smallest aperture number) whenever possible...this is good not only for image separation but it will let in more light to accommodate faster shutter speeds and/or lower ISO for improved image quality. You'll also want to position yourself as close to your subject as you can get and try to shoot at an angle where you have no nearby distractions (tree branches, light poles, etc) in the frame, and the background (foliage, landscape, water, whatever) should be as far back in the distance as possible...and if you're really close to your subject, the background doesn't even have to be that far back to become smooth and creamy.
Worth noting: In the photo of the nursery worker above, you'll notice that I didn't completely blur out the background but rather made it soft enough to not be distracting but still recognizable in order to give some context to the photo. This is commonly referred to as an environmental portrait.
Getting a Creamy Background with Smaller Apertures is Possible
All the shots below were made at f/6.3 or smaller, and most kit zooms can open up at least to f/6.3 even when fully extended (the toucans were shot at f/8 with the zoom extended between 440mm and 500mm):
= new reply since forum marked as read
It would only be too long for someone who isn't interested in following it.
Really appreciate your putting this together!
...but the same rules of photography apply no matter the sensor size.
what you're probably talking about is the "crop factor" and how it can affect the aperture when comparing a lens of the same focal length between the two formats. because the sensor size is about 1/4 the size of a full frame sensor, the crop factor is 2x on an m43 camera. so that means a 50mm lens on one will give you a similar field of view that a 100mm lens on a full frame camera would, though it is still a 50mm lens and it will have all the properties of a 50mm lens. if you want to fill the frame with your subject with a 50mm lens the same way you would with a 50mm lens on a full frame camera, you'd have to stand twice as far from that subject, and the farther you are from your subject at any given focal length and aperture, the more DoF you'll have. so in order to match the full frame field of view from the same distance, you need a lens with half the focal length, a wider angle lens in other words, and the wider the angle lens, the more DoF it will yield at any given aperture and distance from subject. but, it's only one stop of aperture you have to give up. you might feel a bit of pain there with kit zoom lenses but there are plenty of great options for fast glass. and, really, you're going to have the same challenges with kit zooms on APS-C and FF cameras, as well.
i have a lumix G9 and my 3 favorite lenses for it are:
panasonic 42.5mm f/1.7
olympus 60mm f/2.8
olympus 75mm f/1.8
and there are faster lenses than those for the m43 platform, so you really should never have a problem with image separation.
here's a shot i took with my G9 and the 42.5 f/1.7....i was close to the subject but the background was not too far back and i shot it at f/1.8:
same subject, same location, this was with the G9 and the oly 60mm f/2.8 at f/3.5:
this was taken with the G9 and the oly 75mm f/1.8 at f/2.0 and the background was quite close to the subject:
the m43 platform is great and the cameras and lenses available are wonderful. don't let the spin about crop factor deter you. grab a nice fast prime lens and go out there and have fun and make great images.
Sometimes, when clutter is messing up a nice picture
I get out the chainsaw and "disappear" the mess. Reduces wildfire risk, as well.
P.S. I have sent suggestions via DU Mail. It's discreet and has helped people make some bespoke adjustments.
P.P.S. My Z5 seems to always choose the widest aperture when in AUTO mode. If I want more depth of focus instead of less, I use that as a starting point, most often for Aperture Priority.
The following is shot at f/10, and I got as much in focus as I could. The little visitor was just outside the zone of focus and since I needed 1/80 second exposure, affected by motion blur as well. Even with a mirrorless camera, catching speeding objects is always a "click and hope for the best" situation. Worked out OK. It was a lucky catch.
That's rabbit brush. Probably the last flower that hasn't turned into a seed puff.
Needless to say, with close-ups, a background that's 6 inches or more from the subject will likely be blurred.
Very wide-angle lenses give too little working distance.
I try to get tonal separation between subject and background, if at all possible, and I am often scrambling around for the best angle. Focal length was 100mm. here.
I used manual focus, with focus peaking. It's faster for me than moving a point focus around the scene when prime focus is not in the center. Also works great with all the old manual focus lenses, a big plus of the Z5 design.