All posts by ansius

Understanding exposure (ISO vs. f-stop vs. shutter)

Photography is a creative means of sharing an emotion or a message, yet it is still a photochemical or photoelectric process bound by physics rules. Understanding exposure is way to master the mathematics of the physical phenomenon and making it to comply with you creative needs.

Understanding exposure scares even photographers, because some deem it unnecessary, others – to complex, and most – don’t even bother, because most of decent cameras do exposure assessment automatically, and in more advanced cameras you can even chose it to prioritize some of the settings and compensate with others. Like sports mode goes for shot shutter and tries to compensate lack of light by boosting sensitivity (ISO, DIN, GOST) and opening aperture (f-stop, iris or diaphragm), or portrait would keep the diaphragm open for nice blurred background, and so on. Continue reading Understanding exposure (ISO vs. f-stop vs. shutter)

Deflickering time lapse

When ever we shoot time lapses we always go to manual mode, yet it is not always possible. Especially with the holy grail of time lapse – sunset / sunrise. Delfickering time lapse is the hard part. Such time lapses are the most tempting ones, and also technically cumbersome, almost, because there is a twist.

You have to shoot them them in one of the 4 ways, manual exposure (you control the shutter speed), Av priority automatic exposure (camera controls the shutter), bulb ramping (intervalometer changes the exposure by a set curve or keyframes) or the last, and my favorite, auto ETTR if ML. Problem is tough, as I mentioned earlier is that all of them require deflickering, either manually for the first option or other ways for the rest of them. Continue reading Deflickering time lapse

Dual ISO from Magic Lantern, supertool really?

UPDATE: after noticing that actually some people read my articles, I’ve decided to update and extend ones of interest, this one has been the most popular.

I have mentioned in my previous posts of an beast called Dual ISO, but never really explained what is, its benefits and cons, and how to deal with it.

It is a nice feature in ML hack – in essence it gives you a picture that contains exposure in two different ISO.  How it can be? Simply because the sensor is not set to particular ISO, it’s read with a certain gain to achieve the desired ISO, and then converted in ADC to actual pixel brightness values (I simplified, but in essence it is like that). ML then have every other line read in different ISOs, back and forth. And here the trouble starts – you lose vertical resolution – because when you combine those lines they are considered as HDR  pair and saved into a DNG raw file. There are more problems but on that later, below. Continue reading Dual ISO from Magic Lantern, supertool really?

Understanding Exposure To The Right (ETTR)

I stumbled on the Automatic Exposure To The Right – ETTR when I wanted to have bulb ramping feature of Magic Lantern and could not find in my 7D build. Bulb ramping was replaced with the conjunction of those two to give even better result. How nice of them, tough if somebody would have explained how to use it in real life. I had to spend couple days in ML forums and had to do some tests to understand how those features actually work. and when you add the dual_iso to the mix it gets very complicated at first. Continue reading Understanding Exposure To The Right (ETTR)