A wet Sunday and reflecting on technical RAW image quality

Here's a response I posted on at a DPR forum:

Question

I was looking at the reviews on dpr and wanted to know about RAW image quality.  All other things being equal is RAW image quality the most important?  I mean isn't that the "real" picture?

Response

The most important, in no real rank sequence are:

• The shooter - at least 80% of the picture. I have repeatedly seen Grumpy Old Conservatives (sometimes I am one of them) proclaim that gear A is so bad that it could not be used for activity X and then wait a few months, look around and voila, some unknown person on the other side of the internet produces an image which is spectacular.
• The ability of the shooter and camera to get exposure "right". Some people rely on the camera a lot, others rely on themselves a lot. Those who rely on the camera need the exposure to be "just right"
• The ability of the shooter and the camera to get the focus "right". Again some people rely a lot on the camera, others are more tolerant
• For their needs, some shooters rely on the in-camera JPEG engine to get it right. They have no patience or persistence to sit at the computer and process data, their skill is in the field - composing, choosing the "decisive moment" - you can get gear that is technically perfect (i.e. 99% better digital quality vs 80% digital quality) but the image sucks because the shooter is a dud and gets composition, focus, exposure, depth of field or the moment, wrong.
• RAW quality is technical quality - in order to render on the screen, a human or a program has to initially preset the choice of gamma transformation curve, colour saturation, sharpening, aberration correction, perspective correction. Any image you see on the screen that is recognisable to a human, has been rendered with these rendering parameters - the rendering is not about technical perfection it is about visual choice - the two do not have to be equal.
• The RAW quality is the sensor and image processing pipeline quality - if you pick a camera which does not have the lens you want to use or the lens quality that you want, then the image could suck.

The Four Stages of Exposure Awareness

Stage 1: The first thing that newbies learn about is that there is an Exposure Triangle. Some Peterson guy is said to have wrote about it in a book. I haven’t read it. I’ve seen his videos. Maybe his intentions are good and he knows what he’s doing. But a heap of newbies don’t “get it”

Stage 2: Eventually it dawns on people that the Exposure Triangle has a Fourth Side.

Stage 3: After rummaging around, comparing effective techniques of whether to use P A S M or figuring out which metering pattern is better – Evaluative Matrix vs Centre Weighted vs Spot vs the classical Sunny 16 rule vs Interpreting the Histogram vs ETTR and asking themselves where the hell they put the white towel / Kodak 18% Neutral Gray Card or the XRite thingamajig, someone mentions that Adams chap who wrote about the Zone System. And bang! Smack on the head. There is no Correct Exposure. There is what the camera measures as an instrument and what the artist (you) choose to convey and interpret. The two are not and do not have to be the same thing

Stage 4: So far, so good. People are shooting decent shots. But they’re not spectacular. Like those gorgeous smooth skin tones and sharp, clear irises of the girls in the portraits. And so on. So we ask, how on earth does so and so get this shot with his iPhone but we can’t and we’ve almost spent as much as a Nikon D3s? And the penny drops. We can’t. If we REACT to the scene. Often times, the pros don’t react, they’re pro-active. They light up the scene the way they want. Or gain a vantage point if they can’t control the light. And having done their utmost to light the scene well, they touch up with Photoshop. Delicately and Emphatically. Not the other way around.

Desiderata

Go placidly amid the noise and the haste, and remember what peace there may be in silence. As far as possible without surrender be on good terms with all persons. Speak your truth quietly and clearly; and listen to others, even to the dull and the ignorant, they too have their story. Avoid loud and aggressive persons, they are vexations to the spirit.

If you compare yourself with others, you may become vain or bitter; for always there will be greater and lesser persons than yourself. Enjoy your achievements as well as your plans…

When I was in school, this Max Ehrmann poem was all over students’ doors, walls. It’s since lost favour in this world of incessantly competitive and vexatious world of internet forums and dropped remarks.

As I participate in DPR forums, the Beginners Forum reveals lots of insecurities and misconceptions. Lots of people want better photos with the elusive Image Quality (IQ) – they think that getting a better camera magically creates better photos. We keep telling them that 80% of the photo comes from the envisioning + patience + persistence + evolving skill of the photographer. Particularly when one starts from zero base. And a 50% improvement in equipment performance is 50% enhancement of the remaining 20% due to gear. Certainly a skilled craftsperson can and does benefit from heavy investment in better gear but encountering that boundary requires a enlightened understanding of that encounter.

I’ve shot the scene above, many times, under different weather, different seasons, with different cameras at different times of day. Whilst persevering with my Kodak P880 a few days ago, I was evolving my approach. The P880 is a love-hate camera for me – it can surprise with amazingly clear and detailed photos (usually in the hands of someone who lives in Devon, England or Greece) and amazingly unspectacular, nondescript photos. And this scene has shown all the variations.

This time it works for me. Nicely detailed foliage, stone and wood. Sky not burnt out. Strong colours but not distractingly burnt out.

ISO 50. Matrix Metering. Programmed Mode. EV – 0.7. In-camera contrast at max. In-camera sharpening at max.

del.icio.us Tags: Kodak,P880,Beginners,Photography

Telling A Story

Image by Ananda Sim 88 via Flickr

It’s been on my mind to write about the aspects that I appreciate in photos – both my own and other peoples’. At first pass, one would think that the Technical Image Quality Aspects of a photo dominate appreciation of photos, but no, not really. There are quite a few photos that I have seen, and maybe you have to, that are iconic, stand out keepers despite of the fact that they may rate poorly in the Image Quality aspects of exposure, sharpness, colour and so on.

So what is it that we subconsciously search for in a photo when we look at it? It’s that the photo needs to tell us a story. A story about the scene, about the subject, about the object, about the air and feeling, the mood, the time of day, that location on earth. The essence.

To convey some essence of the subject or scene then, the photographer needs to convey some adjective or adverb about the object or about the environs, about that time of life.

On the other hand, what makes a photo just discardable floatsam and debris, regardless of the technical superiority? It’s when we don’t connect to it. The photo could be beautifully posed, shot and post processed but if it says nothing to me, it’s a “next please”. Have you heard of the phrase “ill fitting clothes?” That doesn’t mean the clothes are cheap or dowdy – that just means that the clothes don’t fit the person – and when there have been times in the past (and will be times in the future) when we effect a look, just for sheer trying, that doesn’t match the topic that we are trying to convey. So there. In a nutshell.

del.icio.us Tags: composition,photography,postprocessing,imagequality,storytelling

What is Correct Exposure Part 2

del.icio.us Tags: exposure,dof,shutterspeed,f/no,photography

The Perfect Picture’s Creatively Correct Exposure video tutorial is interesting to watch, but it encourages newbies to link two different facets, “technically correct exposure” and “creative choice of f/no for depth of field” without a seam. Sure, a veteran photographer juggles both these facets intuitively.

The newbie though, does need to pause and think that these are two facets – they overlap in the fact that the f/no is present in both facets but that’s the only thing they overlap in. Otherwise the spiral of confusion, that winds into equivalence of every facet (f/no, shutter speed, ISO, sensor size, focal length) perpetuates.

In truth, Bryan is demonstrating exposure (the permutations of shutter speed and f/no). He’s not speaking of twiddling the ISO dial (because in the film days, you could not easily change ISO in mid roll) nor is he talking about the effect of different digital sensor sizes and focal length.

Bryan Peterson explains this slightly better in this second video – emphasising choice of shutter speed:

and another video, emphasising f/no

In truth, Bryan's videos and the title of this very blog post should be more aptly changed to "Choosing an aperture and shutter speed permutation to effect creative control of the visual aspects of the photo" rather than "Understanding Creative Correct Exposure". Because we have not yet begun to discuss whether we should underexpose or overexpose a scene (in modern parlance on a digital camera, twiddling the Exposure Value compensation dial, to creatively darken or lighten the whole photo so that we can target the face of a person as the most important element in the photo.

Interpreting The Histogram

Lots has been written about the Photographic Histogram. Many people still don’t understand what it is and what it does. Here are my notes:

What the histogram is

1. The histogram is a coarsely scaled and over small 2D representation of the tones. Some cameras have separate RGB histograms.
2. The histogram has two edges, the left and the right edge of the bounding box
3. If it looks like a peak has a slope extending past a box edge it means that there is some technical data that has been lost / will be lost regardless of RAW.
4. RAW has a higher latitude because the contrast curve is not "baked in" and the camera histogram may not show the RAW histogram, it may show the histogram of the embedded JPEG in the RAW. So, you infer that you have half a stop or more of latitude even though the in-camera histogram is showing that there is a truncation of the slope or tail of the peak.
5. With cameras with LiveView, the histogram is a predictive forecasting tool - it tells you before you press the trigger, what could be captured in tones. Shooting RAW or shooting a bracket of 3 or 5 shots is *NOT* a predictive tool - you have made the shots, you can retire without seeing the shots or you may take the time looking at the shots in camera - either way, you have lost oppurtunity or time. This lost time may be ok for a landscape shot but not useful for a quick assessment of a marching parade or anything in motion.
6. Some cameras don't have histograms
7. Some cameras don't have a good EVF or an LCD (e.g. my Kodak P880). This causes me to underestimate the visual quality of the image.
8. Some cameras have an over beautiful EVF or LCD (e.g. the newer Canon G models and reportedly the Panasonic LX-3, the Nikon D90 DSLRs set....). This can cause people to overestimate the visual quality of the image.
9. Some cameras don't have auto bracketing e.g. the Nikon D60.

What a histogram IS NOT

1. The histogram does not measure the visual quality of the shot. It is after all a crude 2D graph of tones.
2. The histogram does not tell you which subject or part of the subject constitutes the tail or slope of the peaks that is being cut off.
3. There is no "correct" histogram - the idea of "correct" does not apply because of points a. and b.
4. The histogram does not tell you how to compose the shot.
5. The histogram does not tell you what is wrong with the shot. It does not advise you that you are shooting into the sun, it does not tell you that you could enhance detail and micro contrast by changing your position and your lighting angle. It does not tell you that your metering pattern is inappropriate. It does not tell you that you are metering for a 12% grey target when you are facing white snow.
6. The histogram does not tell you clearly how much to compensate in EV - i.e. how much EV to dial in to move the peak and thus the tail of the hills. You can do some experiments and gain some understanding by dialing in EV and shooting a test subject. And watching the histogram move horizontally. You do that as homework, not on the day.
7. The histogram does not tell you how much tail to chop off or to force into the bounding box - that's your choice and you have to visualise using whatever method you understand (zone system, experience with the subject etc....). This is a human, visual assessment, certainly the computation and artificial intelligence is getting smarter but the histogram isn't - the histogram is a crude 2D graph.

If a person does not understand how to use the histogram, there is nothing stopping the person from doing a bracket of shots or interpreting visual quality by looking at the LCD screen or the EVF.
The histogram is an informative and useful tool above the:

1. It's sunny so I use f/16 1/100 @ ISO 100
2. Oh, the meter says it is EV 17 @ ISO 100
3. Heck, I'l just dial RAW and shoot a bracket of 5 shots at .3 intervals, one of them should work.

If a person does not want to use the histogram and has some magic recipe that works for them, just do it.

del.icio.us Tags: histogram,photography,LCD,image quality,EVF

The Question: The best Image Quality in an entry level DSLR

Image via Wikipedia We often see newbies say "Please recommend the camera with the best IQ (Image Quality)". Invariably, the most common and sensible reply is "All current model DSLRs do a fair job - pick the one you like the most - go to the shop and hold a few and buy the one that feels good"

There are problems with The Question and there are problems with The Reply, even though each party is sincere in their conversation.

Let's deal with The Question in this post:

1. The DSLR with standard kit lens(es) will give varying levels of satisfaction. On most models, the kit lenses are made to just hit the targeted price level. It's not about photo quality, it's about business. It's like those mini, all-in-one hifi units. The makers can design electronics very well and the account for most of the manufacturing cost. The speakers are chipboard boxes wrapped over cheapboard units. It's nearly the same with the entry level DSLRs - the makers spend money on making a fair body but when it comes to the lenses, they tack on the cheapest units they can. After all these lenses are often not sold separately (i.e. they may not even merit a standalone price). The lenses are just so that the body can be sold.
2. So, most newbies will say, "OMG, the whole kit already costs more than my Point and Shoot camera and it's still not, like great? You mean, I have to buy some more lenses?" Unfortunately, dear, the answer is "Yes" - Many Olympus entry level DSLR buyers may be exceptions to this case, but in long term, even they would feel the need for a brighter glass indoors.

So, The Question is real wrong.

1. The best Image Quality in an entry level DSLR package doesn't come from the package or more importantly, the body. The package in general will give you mediocre to reasonable IQ but not great IQ - the lenses may be less than sharp, will often be dark and may not have the range of angles (wide or tele) that you eventually want or are accustomed to from your Point and Shoot Ultrazoom.
2. If you spend over-much for a class, quality body, you don't have enough money left over for good lens(es).
3. If you go for broke and make yourself broke by buying the biggest and baddest body and brace of lenses, eh-ah, you've got yourself a bigger problem - you'll be feeling like an idiot as you would be the weakest link in the IQ chain.

Come up with a better and more relevant Question. Please!

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