cgarcia
Offline
• •
Upload & Sell: Off
|
DannyBurkPhoto wrote:
Your method should be perfect, Fred, if the camera actually meters strictly on the highlights...but it apparently doesn't! Maybe it's "priority" unless it feels like doing something differently. 
Some days ago I did a interesting test in a sunny and contrasty day to compare the 3 main metering methods usefulness in that particular environment (very common in Spain :-). During a city walk, I took the main shoot carefully using "Entire Screen Average" metering and the zebras for the perfect ETTR exposure, in Av mode (so the EC goes registered in the EXIF data). Obviously, some minor specular highlights were sacrifized here and there, but the main intent was conservative. After this "artistic" shot I took a couple of additional quick shots (but still trying to frame the exact same scene) using Highlight priority and Multi metering modes, both with EC 0 so the camera metered scene was also registered in the EXIF data. I was patient enough to do this with all the shots (35 photos).
At home I compared the perfect ETTR exposure (achieved with certain manual EC in Average metering) with the other metering modes, calculating in a spreadsheet the EC they'd require to achieve the same exposure (same absolute exposure value). The results show that no metering mode is fine. One usually needs to dial EC to optimize the Av autoexposure. In fact, the Sunny 16 rule in manual mode is not only more accurate than the camera autoexposure modes, but saves you from dialing EC :-). Welcome again to the sad fact that not a single Digital SLR manufacturer has implemented to date a proper automated RAW ETTR exposure mode... and ONLY Sony gives the photographers a configurable manual RAW ETTR exposure mode (the zebras) albeit not configured from factory...
In summary, the Average metering required in average a +0.2 EC, while the Highlight priority needed +1.25EV. Only the Multi metering required an average of +0EV... but only a third of its shots were fine at around 0 EC (a 43% required a positive EC and other 23% a negative EC). The same random results applies to the other modes (except the Highlight priority, which never required negative EC).
Here is a capture of the data. Each row represents the same photo (my Average metering 1/3 and 2/3 EC values rounded to 0.3 and 0.7, but the other metering deducted values may end rounded to other close frontiers):
http://etherpilot.com/photo/expoa7r3/a7r3_ettr_ec.png
For using the zebras as a guide, I setup a custom zebra level of 108+ at the camera bare defaults. At home, all pictures were ETTR exposed as intended (by looking at the true RAW data). I usually have a picture profile enabled with HLG gamma, but for this test I disabled it, because otherwise every metering mode becomes about +0.5EV more conservative, and I wanted to generate "default" results here. And by the way, why the heck the entire camera metering depends on a active "picture profile" settings?. Any camera metering in a given mode should only be related to the scene lighting, or am I missing something?
Anyway I'm happy with the A7R3, thanks to the zebras fine control when you have time to meter (which I usually have).
|
I thought you reduced your exposure to preserve highlights, then lifted shadow areas. How do you keep from clipping highlights when you increase exposure nearly two stops?