Highlight Tone Priority

Many shooters leave Canon's Highlight Tone Priority on to guard against overexposure of highlights in an image. This is particularly helpful in wedding photography where the meter is often presented with a black tuxedo next to a white dress; maintaining some detail in the dress is key to a good shot. To achieve this, the camera raises the minimum ISO to 200, allowing for a stop of exposure recovery when bright highlights are present in the image. It cannot recover from all specular highlights, as the sun is a very bright object, as are its reflections.

HTP off - ISO 100, F8, 1/200, 63mm w/15-85mm 100% crop
HTP on - ISO 200, F10, 1/320, 63mm w/15-85mm 100% crop

In the sculpture above, sunlight is directly reflecting from the polished stainless panels. Many of these are unrecoverable in both shots, but more are recoverable in the shot with HTP active. The crop above shows a panel that appears almost completely blown, but which has quite a bit more detail in the HTP version. In short, it's not a guarantee against blown highlights, but it helps. The drawback is that the lowest ISO available is 200.

High Dynamic Range

Love it or hate it, High Dynamic Range mode can come in handy in difficult scenes, bringing up detail in shadows, and saving highlights at the same time. The Canon EOS 70D has four HDR modes: 1 EV, 2 EV, 3 EV, and Auto, the latter of which seems to pick among the three modes depending on the difficulty of the lighting situation. Optional Auto Image Align crops the image slightly to give room for cropping, which comes in handy when shooting HDR handheld. The cropped area appears in the viewfinder when Auto Image Align is active.

HDR Auto

Because the camera's taking three exposures and combining them into one, any subject moving in the frame will result in ghost images. The Canon EOS 70D makes an effort to remove duplicate subjects, but has limited success with complicated scenes like this one. Subjects moving toward the camera are harder for the camera to detect, so you'll see some people with odd borders around their bodies. In the HDR Auto image, a man is walking behind the railing, and the camera finds and removes the other two instances of his body above the railing, but ghosts of his legs continue to walk along without him inside the railing.

Overall, the HDR mode works pretty well, bringing up detail in the shadows without looking too artificial. However, as one who usually shoots Raw+JPEG, it's pretty frustrating that HDR mode is grayed out until you switch to JPEG-only. The camera should do that automatically and warn you it's made the change.

Auto Lighting Optimizer

ALO has come in handy more often than not, particularly for snapshots of people. For those who also shoot Raw and process in Lightroom, it can still be handy to have ALO's pre-processing ready to go in a JPEG. This shot below is a good example of what ALO can do.

ALO off - ISO 100, F5, 1/80, 50mm w/18-135mm ALO Standard

The first image is the Raw shot reprocessed in the camera with ALO turned off. The second image is the JPEG from the original exposure, which was captured with ALO Standard enabled to boost the shadow areas. It's a little overdone, but for a quick camera-to-phone-to-Facebook post, or a printout for the scrapbook, it's good.