It seems that some pictures I’m taking just aren’t tack sharp, I’ve been shooting in Aperture Priority and I’ve made sure to avoid camera shake and such. Based off the picture below what would be a reason on why the face isn’t as sharp? I’m shooting on a 6D II with a 85mm lens. My focus point is on the face and yet still no sharpness, I’m not using the center point as I feel that recompositioning results in blurry images and instead I’m moving to the point closest to the face.
I don't think you're lacking in sharpness: at full size, the image you post shows sharp eyelashes and teeth. If you are using a large aperture (<F2), that explains the unsharp ears.
When you reduce the size at which the image is displayed, apparent sharpness tends to decrease. To get the impression of sharpness back, you'd have to apply some sharpening after downsizing.
Another factor is the contrast of the face, which in this case is rather low. That also tends to give the impression the image isn't sharp. Local contrast enhancement can be useful in such cases.
I wrote "impression of sharpness", as the usual sharpening techniques increase the contrast at edges in the image, which increases the acuity. It does not increase the resolution of details in your image.
There are some methods that can increase the level of detail in your image (up to a point), by using Fourier or wavelet transforms. Those methods are rather complex, slow, and can easily give rise to (very ugly) artifacts, but when applied with caution they can give you extra detail.
In summary: you could use a smaller aperture to get better depth of field, and do some editing (mainly sharpening, perhaps Local Contrast Enhancement) to counteract the effects of the low contrast and size reduction. (Even your full image as shown here isn't 26 megapixels).
Looking at the example image at full magnification, it seems that the sharpest part of the boy's face is the tip of his nose. If you look at his left hand (camera right), you see that the area from around his fingers' first knuckles back almost to his wrist is the sharpest part of the entire photo.
This could be due to:
- You placing the AF point on his nose.
- The PDAF system is slightly out of calibration and your camera is front focusing slightly. This can be corrected using in-camera AFMA (Auto Focus Micro Adjustment).
- You are correctly focusing on his eyes, but then you or he are moving slightly between the time you lock focus and the time you take the photo.
- You are using 'Zone AF' with nine points enabled and expecting it to work like 'AF Point Expansion' on other Canon cameras, where the center point is given priority. With 'Zone AF' all nine points are given equal priority and the camera will usually focus on the nearest object within the area of sensitivity.
Most 85mm lenses have fairly wide maximum apertures anywhere between f/1.2, f/1.4, and f/1.8. At those apertures and your shooting distance Depth of Field (DoF) will be razor thin. If the camera is focused on the tip of his nose, the parts of the face further back will be progressively blurred fairly quickly.
But beyond that, you might be confusing 'sharpness' with 'contrast'. Even when two subjects are equally "sharp" in terms of absolute resolution, the object with higher contrast will look "sharper" to our eyes. There's not much contrast in your subject's face. This is mainly due to the strong backlight in the scene. To make the subject's face "pop", it needs some light shining on it from an angle that allows it to illuminate the front of the face.
Remember those parts of his left hand that look the sharpest? They're being illuminated by some reflected light from the sides that give them more contrast than the center part of the same hand that isn't getting any texture defining light - just like the middle of the face.
If you shoot your 85mm f/1.4 or f/1.8 wide open at a close distance - you DoF is quite tiny (http://www.dofmaster.com/dofjs.html to the rescue). It's really hard to tell looking at the small example image, but the eye lashes and eye brows seem in focus to me. Are you using your OVF (optical viewfinder) or the LV screen? If the first one - run a calibration test to make sure there is no play between your lens, the PDAF array and the sensor. I use Reikan FoCal, but there is a bunch of free DIY or cheap alternatives. You may also try to use the LV focusing (with or without face detection), which employs Canon's dual pixel AF. it's always accurate but probably not as fast as PDAF. And finally, different lens produce different sharpness. The sharpness is always at its lowest point when you shoot wide open regardless of the lens. For an average f/1.4-f/1.8 lens the best sharpness would be around f/4 - f/5.6, which probably won't give enough background blur, but your subject will be perfectly sharp. After f/8 (depends on the sensor pixel size) the sharpness will also degrade due to diffraction.