Sometimes even the best make mistakes. What is important though is that we learn from them.
The other weekend, I was at a friends wedding and taking photos for fun. What was not fun was editing those photos; they were mostly blurry or not sharp. *note, i'm very picky about what is a good photo** What is usually my normal ratio of 1 in 5 (1 in 5 are good, use-able photos to share/upload) was over 1 in 25. It was like when I started photography 7 years ago. I of course took some really good photos, but the ratio bothered me and I checked online what I did wrong and found out that I forgot 3 important rules for sharpness:
1. Having a fast shutter speed, specifically longer than your lens length
- I was using a 90mm and only using 1/60 shutter speed. In normal situations 1/60 is an acceptable speed to freeze motion, and (b/c I wasn't 'seriously' taking photos that night) didn't bring my flash for dark, indoor photography
+ it would have been better to use atleast 1/90 or faster to increase sharpness
2. Do Not shoot wide open. //This has always been hard for me to explain but:// basically your f-stop.. don't use really small numbers like 1.4, 1.8, 2.#
- I was using f1.8.. once again, no flash, so to avoid underexposure, used that. Problem with that is that f1.8 leaves an extremely small margin for error.. the best photos always have pinpoint sharpness/focus on the eyes of the subject (unless doing something artsy)
+ there is an apparent 'sweet spot' of sharpness on each lens
+ I would recommend around f5.6+
note: shooting at f1.4, 1.8 etc can result in desirable blurring of the background, just if your other setting aren't correct, more than just your background will be blurred/not sharp
3. Use low ISO
- with low(ish) shutter speed and shooting wide open, I had to have rather high (1600) ISO
- I've read on some sites that adding grain to the BACKGROUND can increase sharpness.. but I don't imagine grain on your subject contributes to that
- I've never liked the way photos looked at high iso anyways, altho I've found, the newer/better the camera (I've gone from D200 to D300s to D750), the better higher iso pictures look
+ (obviously) it would be better to have a maximum iso at 400.. preferably as low as possible
Honestly, in the future, if I intend on using my camera indoors, I'll be using a flash, which can resolve all three. It'll provide the brightness to allow a quick shutter speed (1/200, 1/250), a low iso (200-400). I would still use a high f stop number, unless I was doing model photography/no movement.