This is an amazing article I wanted to share. It goes through, in incredible detail of how to make your photos look sharper than ever. This is part 2!
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3. Optimal Exposure When You Have a Shutter Speed Limit
If you’re trying to freeze a moving subject or shoot handheld, there’s probably a limit to the longest shutter speed you can set. In turn, that requires compromises in the ISO and/or aperture that you set.
And this is where things get a little messy.
3.1. Shutter Speed:
First, keep in mind that every photo has an optimal range of shutter speeds. When you find that range, you really don’t want to go outside of it. Too much motion blur can ruin a photo in an instant.
So, what exact shutter speed should you set? Ideally, you’d use the longest possible shutter speed that still completely freezes the photo’s motion. As an example, if you eliminate motion blur with a 1/125 second shutter speed or faster, 1/125 second is the perfect shutter speed to use. It’s the longest exposure with zero motion blur, meaning it captures as much light as you can under the circumstances.
Here’s the 100% crop (click to see full size)
However, you’ll rarely know the exact shutter speed cutoff for a given scene. It requires some trial and error in the field, although practice and experience are good substitutes. Once you do find the range of acceptable shutter speeds, it’s best to stay within that range no matter what – or, at most, go about 1/3 or 2/3 stops longer than ideal.
That’s because shutter speed blur is one of the most annoying image quality issues you can have. If it’s too obvious – and it gets too obvious in a hurry – it can totally ruin an otherwise good photo.
In tricky situations like fast-moving sports photography, it’s possible that some photos will have different shutter speed cutoffs than others. In those cases, it’s best to play it safe. Just go with the shutter speed that makes every photo sharp, and don’t worry if you could have snuck in a slightly longer exposure on a few of them.
3.2. Aperture and ISO:
Next, it’s time to figure out what aperture and ISO values you need to use in order to accommodate your shutter speed limitations.
If you’re already shooting at your lens’s widest aperture, just raise your ISO until the photo is bright enough. But if you’re at a narrower aperture, you’ll often need to widen it in order to capture more light.
And that’s when you get into the tug-of-war with ISO. Specifically, is it better to have too high an ISO, or too shallow a depth of field?
There’s no perfect answer, although I do have a preferred process for my own work. Up to ISO 400, I just raise the ISO. Beyond that, I’ll trade off: a third stop wider aperture, then a third stop higher ISO, then a third stop wider aperture, and so on until the photo is bright enough. Find a similar method that works well for your gear, and you’re set.
3.3. ISO Invariance
One exception to the technique above involves the weirdness of ISO as a photographic concept in the first place.
To distill the issue down to a single question: Why raise ISO when you can simply brighten an image in post-processing?
Usually, the answer is that you get better image quality by raising ISO in-camera rather than brightening in post. But that’s becoming less and less true over time, as camera sensors become “ISO-less” or more accurately ISO invariant at some point in their range (or across the entire range).
With my previous camera, the Nikon D800e, this occurred at ISO 1600, although it wasn’t far from ISO invariant at the lower ISOs. In other words, up to ISO 1600, it was worth brightening the photo using the in-camera ISO. Anything more – 3200, 6400, etc. – provided no image quality benefits. Plus, the higher ISOs increased my risk of overexposure in highlight details, especially pinpoint highlights like stars.
Not all cameras are as simple. For example, the Sony A7R III is ISO invariant across two ranges: ISO 100 to 720, then ISO 800 and up. So, if you only ever used ISO 100 or 800 on the A7R III, you wouldn’t be losing image quality. If your photo is underexposed because you would have used one of the other ISOs, just brighten the image in post.
Of course, ISO invariance is controversial for a few reasons. The big one is that it makes it harder to preview images – and it also adds more time in post-production. Plus, most post-processing software is not made for giant boosts to image brightness, so you might get some color shifts or other artifacts when doing extreme shadow recovery.
I’d say it’s only worth worrying about ISO invariance for one specific case: astrophotography. There, shooting at too high of an ISO can blow out color details in the stars, while shooting a lower ISO and brightening in post-production can retain those details. Personally, I avoid ISOs beyond 6400 for astrophotography for this reason, even if it requires a bit of brightening in post-production.
Otherwise, make your life simpler and don’t worry about ISO invariance. After all, brightening a photo in post-processing doesn’t give you better image quality than increasing ISO in-camera; it just protects highlight details more, without harming image quality.
If you’re not shooting a scene like stars where the highlights need special care, it doesn’t bring any other big benefits.
4. Other Camera Settings
The exposure settings above are very important, but there are a few other camera settings which are worth noting if you want optimal image quality.
4.1. Shutter Mechanism
I recently wrote about the three common shutter mechanisms today: mechanical, electronic, and electronic first curtain shutter (EFCS).
You should read the comparison to see all the differences in detail, but the takeaway is simple: Use mechanical when there is artificial light in your photo, and electronic otherwise – or EFCS if your camera doesn’t have an electronic shutter.
4.2. Mirror Lockup
Along the same lines as setting your shutter mechanism properly, you also need to get rid of camera shake from mirror slap (only on a DSLR, of course) and simply from pressing down on your camera, even if it’s on a tripod.
For this, I recommend using mirror lockup mode in combination with a brief self-timer, such as two seconds. Or, if you’re a Nikon shooter, “Exposure Delay Mode” makes this simpler by raising the mirror when you press the shutter release button, pausing for a second or two so vibrations dissipate, then capturing the photo.
4.3. 12-Bit vs 14-Bit RAW
Many cameras today have a RAW image quality setting that lets you choose between shooting 12-bit or 14-bit color.
John Sherman already showed that anyone who shoots 14-bit RAW rather than 12-bit is a paranoid pixel-peeper. And today, that’s exactly what we are!
If you’re using the (very slightly) lower quality 12-bit RAW setting, rather than turning it up to 14, how can you possibly claim to be capturing maximum image quality? Also, something about storage being cheap, and so on.
4.4. RAW Compression
This one does actually make a difference – RAW compression. Most cameras let you choose between uncompressed, compressed, and losslessly compressed RAW. Some omit the “lossless” option.
Of the three, lossless compression truly is lossless; there is zero image quality detriment to using that setting. It’s my strong recommendation.
If your camera only has “compressed” and “uncompressed,” go for better image quality. Uncompressed RAW photos take up more hard drive space, but they’ll show some definite image quality benefits in certain cases.
4.5. Long Exposure Noise Reduction
When you’re shooting with long shutter speeds, there’s an important camera setting to keep in mind: Long exposure noise.
With this mode enabled, the camera takes two photos in a row. The first is your actual, main exposure. The second is a dark frame with the shutter curtain closed, captured with an equally long exposure as the first. Your camera then uses the dark frame to subtract out noise and hot pixels from your main shot.
This does affect RAW photos, and it can make a real difference when you’re shooting especially long exposures. I hate the wait as much as anyone else – it takes twice as long to capture these photos, since you’re taking two photos – but in the race for maximum image quality, what’s an extra 30 seconds in the field?
5. Image Blending:
If all of the above isn’t enough for you, the most in-depth way to improve image quality is to blend multiple photos together.
This can take a few different forms. The most obvious is creating a panorama, since you’re able to increase the resolution of a photo drastically – no real upper limit, aside from how long you’re willing to spend stitching the photo together.
HDR photography is another big one. In high-contrast situations, getting enough highlight and shadow detail simultaneously may be impossible without blending photos together. HDR increases your dynamic range, and, when done right, decreases shadow noise as well.
There’s also Focus Tracking – taking multiple photos focused at different distances, then combining them into an exceptionally sharp photo from front to back. This lets you use your lens’s “sweet spot” or target aperture and still get enough depth of field, making for extremely sharp photos.
Lastly, you can use the technique of Image averaging to reduce noise and improve dynamic range. This is especially Milky Way photos, but also applies to a few other situations, like drone photography or as a replacement to HDR.
A few other types of image blending exist, but these are the big ones in terms of image quality.
The real question, however, is whether or not you should actually put any of this into practice. My answer is – by default – you shouldn’t. Photo blending has some serious potential to go wrong, especially if the light changes or your subject moves from shot to shot.
I tend to blend images only to salvage photos that wouldn’t work any other way, not to boost image quality for its own sake. But that’s just me. Again, this article is about the things you can do to push image quality to the next level – and image blending clearly qualifies.