Focus bracketing and compositing with Canon RF mount cameras and Adobe Photoshop 27 December 2022

 

Canon EOS R5 with RF 100mm f2.8 L macro hand held. Only two shots were required  for compositing from a 5 frame sequence.

In the good old days  of sheet film and view cameras we could manipulate the plane of focus using tilt movements on the front and rear standards. Canon and a few other makers have tilt/shift lenses for 35mm size cameras which enable the same effect. But most of us don’t have one of those lenses.

Fortunately multi-shot focus bracketing and post capture compositing in camera or in editing software can enable depth of sharp focus to extend beyond that which would be possible with a single exposure.

This post is a guide to focus bracketing and compositing using Canon EOS RF mount cameras and lenses and Adobe Bridge, Camera Raw and Photoshop.

Subject selection 

There are two common subject types which can benefit from focus bracketing. These are landscapes, where the concept of a landscape is imagined broadly, and close-ups where obtaining sufficient depth of focus is an ever present challenge.

The closer we approach the subject the more important it becomes to keep both camera and subject still. This because image acquisition involves making a series of exposures in succession, each focussed at a slightly greater distance than the last.  This takes time and you might be surprised to discover how much things can move when they are not secured. The result is that some subject elements will not be in the same position in the frame in each exposure.

Small subject movements of no significance at 5 meters from the camera will seem like wild gyrations at 5 centimeters.

Equipment

Any RF mount camera listed in the specifications as having focus bracketing will do. Some models output and display a JPG merged composite in camera. This process usually takes a second or two to complete.  Any RF lens will do although for close-ups the RF 100mm f2.8 L macro has no peer.

I do not know if EF lenses on RF bodies enable focus bracketing. I suspect they probably do but I also suspect that results are likely to be more consistent with RF lenses due to the extra two way communication these have with Rf mount camera bodies.

A tripod is very desirable for close work as is a tripod collar and foot if one is available for the lens used.

In camera

* Copy Focus bracketing from the camera (red) menu (on the R5 it is on screen 5) to My Menu for quicker access.

* Considerable practice and experiment is required to achieve the best settings for number of shots and focus increment. For landscape subjects fewer shots and smaller increments work well. For close-ups more shots and larger increments are required. In either case I would not often use more than 9 shots.

Enable [Exposure smoothing] in the focus bracketing submenu.

* Be aware that e-shutter is used for focus bracketing with potential for banding with many artificial light sources.

* Use aperture priority mode in the range f5.6-8 and maybe f11 depending on the lens in use and subject.

I recommend Raw capture for best results.

* Generally use Auto ISO but if the subject is well lit and both camera and subject are immobile ISO 100 gives best detail.

* Focus bracketing is possible hand held provided the subject is not moving too much and the stabiliser is on.

When the camera is immobilised on tripod or other support, switch the stabiliser off and use 2 second timer delay or Canon Connect and a smartphone to activate the shutter

* The focus bracketing sequence starts at or closer than the nearest part of the subject then moves by increments to or beyond the most distant part of the subject. If too many exposures and/or too large an increment is set we could see many exposures focussed beyond the far point required to be in focus.

In Canon-speak [Focus method] refers to the size and configuration of the focus area. Using the smallest available size helps us to focus accurately.

To start the sequence place the focus area over the nearest part of the subject and half press the shutter button. Check that focus has been achieved at this point, if necessary with the [enlarge] button on the back of the camera.

* Fully depress the shutter button or other method of starting the exposure sequence as described above. The camera zips quickly through the sequence of exposures.

* With some models a composite JPG is produced in camera immediately.  This has the advantage of convenience and the appearance of an immediate result.

With other models we have to send our sequence of shots to Photoshop or some other compositing programme. These notes refer to Adobe Photoshop.  This has the advantage of more control over the process including frame selection.

If we have a camera model which produces an immediate composite JPG which turns out to be a messup, which happens fairly often in my experience we can revert to the Photoshop method with the saved files in the focus bracketing sequence.

This little weed grows in the spaces between paving stones. Although the distance between closest and furthest points required to be sharp is only about 30mm this shot required 8 frames with a medium increment.

In Bridge > Camera Raw > Photoshop

* Download the sequence of shots and view them in Adobe Bridge at low magnification then at full size on screen. Look carefully at each shot for focus. We might find the first frame of the sequence does not render the near part of the subject sharp but the second or third shot does. Discard the unsharp ones.

Now step through the sequence and locate the first frame which renders the far part of the subject sharpest. Discard any unsharp frames beyond this.

* Transfer the remaining frames to Camera Raw.  Select all the files together. At this stage we can if desired apply some editing to the files provided each file gets the same treatment.

* Open the selected files in Photoshop.

* Go to File > Scripts > Load files into stack.  Check [Add open files]  and [Attempt to automatically align source images].

* Select all layers in the Layers tab.

* Go to Edit > Auto blend layers > Stack images.

Check [Seamless tones and colors] and [Content aware fill transparent areas].

* Close the original Raw files leaving just the composite open.

* Go to Layer > Flatten image.

* Name and save as JPG, or other desired file format such as PSD or TIFF.

* Carry out final editing in Photoshop and/or using the Camera Raw filter and re-save.

* Review the final image for areas of double imaging and /or fuzzy bits which are fairly common. Detail work in Photoshop can often rescue these if they are not too numerous. 

Dealing with double imaging is tedious and usually involves painstaking local removal of unwanted edge doubling using selections and the clone stamp.

Fuzzy bits if localised and small in the frame can be managed in the Camera Raw filter.    In the Masking tab select the Brush tool set to maximum Texture, Clarity and Sharpness and experiment with variations noting the resulting appearance.

End