The Six Keys to Image Quality
Gavin Seim: Some time back I discovered mind bending quality of large format film images. I then become fanatical about getting the best image quality from digital that I could. I want to know what it’s capable of and how to manage it. I’ve been working on a simple way to explain what I learn. I thought of inventing a cool acronym for it, but I decided to be straight to the point and just lay out six key elements that I’m finding directly effect image quality, along with some thoughts on how we can manage them.
Also note that I’m not talking about “at a glance image quality”. I’m talking about facts for people who really care about making their images as perfect as possible. A Facebook image can get away with a lot because it’s so small and the expectation is low. But understanding what you’re seeing when you zoom to 100% will help you understand what your quality means to you, to a wall print, to an art gallery, or to that submission to a stock agency. Also while I’m focusing on digital, all but one of these elements apply to film as well.
Also I should mention that I go even more in depth on this topic in Pro Photo Podcast episode #74. OK lets get started.
Bull of the Mists was made at ISO3200. Pretty high, but otherwise I would have missed the shot. The six keys worked and the result has detail even as a wall print. Read more here.
Six Keys to Great Image Quality.
- 1. Optic.
There’s no way out of this, so get past it. If your lens is bad, so is your image quality. No matter what else you do. A $200 70-200 is not giving you the same quality as a $2000 pro lens. The difference between cheap glass and great glass is huge. If you want great image quality you have to get great glass. Are there variables? Sure. For example a 50mm 1.4 lens is not that expensive (around $400 usd), but it’s known for great quality. Some primes however are even more expensive than zooms. And worth it too. Generally with glass the more you spend, the better you get. But do your homework and get the best bang for the buck. Just don’t think you can get off cheap.
- 2. Sensor.
What your sensor can do and how far you push it will effect your image. If you push a sensor to it’s max capabilities you’ll get lower image quality. It’s that simple. That’s not to say you never should do it. Just know the consequences and know what your sensor can do. If you have a 15 mp sensor on a point and shoot and a 15mp sensor on an SLR, there’s no comparing them. The SLR sensor will retain quality better when being pushed to it’s limit. It’s pixels are less crowded and higher quality and the quality of your pixels is what counts. But no matter what sensor you have, remember that every setting will have a consequence.
- 3. Light.
A well lit scene will give you better image quality because you’ll have to do less to compensate later. This is connected to processing. If you underexpose a portrait or you don’t wait for the right light in a landscape, you can compensate to a point in post production. But at a cost. The more you have to recover in post, the more you lose in quality. For example, a perfectly exposed photo may have great blacks. A photo underexposed by one stop and fixed in post may be a good image, but it will usually have more noise and artifacts. There’s always a cost.
- 4. Focus.
If you’re out of focus, you’re out of luck. Sure, you can use filters or plugins and tricks to enhance a screwed up photo. That stuff is good to know, but it’s just a fallback. Focusing your lens properly and having enough depth of field is irreplaceable. AF is also great, but I’ve missed some killer images because the AF missed. I use AF when I want speed, but sometimes it costs me. At times perfect focus requires the camera be mounted. Macro is a perfect example of this because it’s DOF is so shallow and a little moment changes things in a big way. But even on my landscapes I generally manual focus. AF is not perfect and perfect is what I want. I’ll lock down and set my composition. Then I’ll zoom the live view to 10X and make sure my focus is spot on.
- 5. Stability.
I tripod or mount matters. You can make excuses all day long, but generally if you really want the best quality you should use one. I understand it’s not always practical, but weigh the consequences. If you can use a support, you’ll generally get better IQ. Maybe you can use a monopod in a more active situation instead of a tripod. Look at your options and get the best stability you can. More on this below.
- 6. Processing.
Did you notice that every other key was in camera. Processing key is a big one, but it relies on the ones that came before. If proper editing can make poor photo good and good photo great. Then it can make great photo truly incredible. Get it right in camera, then get it right in process. I can’t explain in a paragraph how to process perfectly, but there’s lots of tips on my Seim Effects site to help with that. In brief, don’t overdo it. Don’t just bump sliders because you can. Don’t use the preset or action that blows the highlights unless you have a reason. A great photo is not made by the editing. It’s made first. Then refined by the editing. Consider what your main subject is (if you don’t have one start over). Consider how through editing, burning, dodging, sharpening, color etc you can draw the viewers attention to that subject in an often subconscious, but powerful way. Nail it.
1:1 detail from Sunsets Hidden Falls. I worked from start to finish to try and maintain good blacks and information. The planning made a difference. More on this image here.
The Wrap Up. Remember that all the keys interact. Say you’re shooting a sunset at 50mm, ISO200 and you’re getting a shutter speed of 1/30. It’s too slow. You might get a decent photo hand held that looks great on FB. Maybe you have really stable hands and you can get a good 16×20. It’s still unlikely that perfection would hold up when you zoomed 1:1. Blurring is a subtle thing. It can go unnoticed when seen small. Believe me I’ve learned that lesson.
OK so you could crank up the ISO to 400 and get around 1/60. Better, but a tripod will still give you more flawless clarity. Technically speaking 1/60 is fast enough for a 50mm (shutter speed should at least match the focal length rule), but just as technically if that camera was on a tripod the tight detail will be better.
OK, so now we crank the ISO to 3200. Now were getting around 1/500. I would still contend that a solid tripod would give you more quality, but that aside. You’re now shooting at 3200. While you might get a clear image, it will be degraded by noise. I’m not saying I won’t shoot at 3200 (I did it above). I don’t mind a little noise, because when well processed it’s almost like natural film grain. That said we’re talking quality. If I use ISO 3200 because I need to get the shot that’s OK. It was required. Bit if I use 3200 because I’m too lazy to set up a tripod, I’m throwing away detail because I’m a slob.
All the keys are cause and effect. If you want the best IQ possible you should think about every one of the six keys. If you can check them all off, you can be pretty certain you’re getting the best quality possible. That’s said there’s nearly always a way to change the game. Better optic, sturdier tripod, waiting for better light, refining your process skills to avoid getting artifacts. The keys are not an exact science and rules of course can be broken if there’s a good reason. Just make sure there is.
Last, lets bear in mind that this is just a basic look at image quality. You still need an interesting subject, good composition, etc, etc. But that’s a post for another day… Gav
Ghosts of Clepsydra Geyser. Here’s a screwup. I made this image and loved it. So did everyone on FB. Well I did not pay enough attention to the keys. It looks great here, but the sky is out of focus (look at the detail below). Crazy as it sounds, I did not even notice this until I got home over a month later and made the first 24 inch print. Some cloud motion would have been OK, as this was a long exposure. But I went back and checked the original files. This is simply not in focus. I should have made sure it was right before I pulled the trigger. This is an amazing scene that will not make my Signature Print Collection because I did not follow the six keys. I can use this for web sized projects, but little beyond that.