Tagged: Back

22nd September 2016 – Quiz Night and More Answers

Quiz Nights. You can’t beat them so we joined ‘em. Thanks to Myk Garton for putting the evening together, I know from first hand experience just how much effort goes into making it look effortless. And of course all participants showed themselves masters of their hobby. This week on the blog we will wrap up two of the three remaining questions from the Week 2 Q by looking at: What is front curtain, rear curtain and slow flash? And what is Back button focus? This week has also been the big European photographic trade show, Photokina, held in Germany, one year I will have sufficient time and money to go …..

Still, daydreaming aside, what is front curtain, rear curtain and slow synch flash? Flash, aka strobes, aka those lighty things, is an area that is both technical and often ignored by the amateur. Yet it is one of the most effective accessories we can purchase. After all most of us have one built into our cameras, even if it does get overlooked most of the time. There is more to this than we will look at here, indeed we will visit this in a future blog, but for now we will explore the question that was put concerning these three often found menu options.

For this specific question we do not have to differentiate between off camera flash (or strobes if you prefer) and on camera (that is pop-up or otherwise built in). The reason behind this is that this is a specific question of the firing order of the flash in relation to the curtain or shutter. Mostly this is done off the position of what is known as the front curtain. The majority of cameras have a two curtain (shutter) set up. This enables faster shutter speeds, the flash synch speed of your camera is actually around about the fastest speed that the whole of the sensor is exposed. Otherwise it is exposed through a slit formed by the front and the rear shutter curtains moving across the sensor plane at a fixed distance apart. The faster the shutter speed the closer the gap.

If you expose using a strobe/flash unit above the flash synchronisation speed you get a dark band of varying width according to the shutter speed as the duration of a flash is extremely short. Because the lens projects things upside down onto the sensor and the shutters move from top to bottom this band will appear from the bottom upwards. Not so much of a problem if you only need light at the top of the frame, but not actually something that is easy to fine control both because of the position of the shutter at any given time and how much darker the rest of the frame is.

So why have a front curtain flash and a rear curtain flash? It’s to do with the motion blur in the frame and where the pulse of light freezes that in time. The least subtle explanation, nonetheless one that actually holds true, is that you use front shutter curtain to freeze the action. You might use your maximum shutter synch speed (often automatically set but that depends upon make and model of your camera body) to give yourself the maximum chance of freezing the action. You use the rear shutter curtain and, usually, a lower shutter speed to freeze the foreground and retain some motion blur in the scene. And slow synch flash? Well that is an automatic camera mode that forces a slower shutter speed and synchronises the flash. You can get some very different looking results from the same scene using these variations. As ever, try it out for yourself.

Back button focusing, once you’ve tried it you will never go back. At least that is what its fans say and there is no denying that it is a very useful tool. We looked at this on the blog last August viz “Back Button Focusing (refer to your manual for the native translation in your Camera’s Brand-Speak) does exactly what it says on the incredibly expensive magnesium alloy tin, or plastic camera body as befits your pockets/needs/delusions of grandeur. It is a button on the back of your camera body that activates the camera’s focusing system in isolation from the shutter release.  When you operate via the shutter release a half pressure triggers the autofocusing system (assuming you are not mounting  a manual lens) and a full depress activates the shutter release. Usually the shutter will not fire until the camera processor detects all the algorithms are in place to produce a point of focus and an acceptable circle of confusion (i.e. something is in focus …).  The button itself is usually marked AF or a version thereof and is normally accessible with the right thumb (I’ve never seen one on the left but then I haven’t conducted a survey in any depth). And it’s on the back of the camera.”

Yeah, that is what it is but what use is it? Well first off there is the fact that, whilst depressed, the AF button means that you hold whatever it is you have focused on. In the automatic modes focus shifts when you shift what you are looking at, which can be time consuming. In order to keep the focusing, for instance if you want to shift the main point of focus to the edge of the frame and blur the background. You might want to add to that you can use the continuous mode (AF-C or AF-Servo depending on your camera body manufacturer) of focusing on your camera when following action and use the AF button to freeze the most advantageous point (takes some practice but worth the effort with a high degree of movement in the frame). Or basically no more having to focus every time you let go of the shutter which takes time and can mean that you loose your shot. Annoying when it was already in focus the last time you half depressed the shutter.

So now you know. Next meeting is Table Top photography, a practical so bring your cameras and tripods. Maybe your flashes too!

10th September 2015 – Bending the Light. Mac Bouchere FRPS.

Mac Bouchere FRPS was the first speaker of the season and his aim was to prompt us to look at things a little differently, sometimes new things sometimes the same things, in his talk “Bending the light”. Mac presented us with a wide range of examples and he talked about the differences that prompted him and the importance to him of pre-visualisation. Not invented by him but certainly popularised by him, Ansel Adams made pre-visualisation a way into getting the feelings behind what he photographed.

 

In essence what Mac was putting across was the next step from getting the camera off Auto. Auto is great at getting good results from a number of situations, but it is not particularly discerning and it’s not really what we shell out all those readies on. The other settings give you increasing flexibility before you ever get to post production and given the minimal marginal cost there is very little to stop us experimenting. What Auto does is make decisions based on the algorithms derived from the analysis of many, many thousands of images to derive a set of averages that can be applied within the dynamic ranges of the chips that are bought or manufactured by the camera makers so as to provide us with acceptable images in those situations. Putting a random, but nonetheless convincing number on that, let’s say 80% of our pictures. There comes a time, as our own Gerry Painter pointed out last year, when those acceptable images are just that. Acceptable. But with something missing. Not quite what we visualised.

 

We can move on to programme modes, that give us a little more control in what we accent and prioritise in terms of light and dark in our images, also in terms of chroma all the way to how much and how intense is black and how much and how intense is white within certain narrow boundaries. In order to truly exploit that we have to explore the more manual options that affect the exposure triangle all the way through to full manual and, of course, post production. Mac’s point was that it doesn’t have to end there and we can, through digitising our print and slide collections, give those a whole new lease of life too. We can push, pull, stretch, colourise, monochrome, blur, merge stain, grain, crop to our hearts content, not just on the images that we take now or have taken relatively recently. Also, and I think most importantly, Mac urged us to get the images we want.

 

He was quite open about the images he showed us, the ones that would never get anywhere in club competitions to the ones that had won medals. The point he was telegraphing by doing this is that, certainly as amateurs, but it extends to professionals too (they just have more limited opportunities to do it and he is one of those), is that we should use in camera and post production techniques to craft the images we have in mind. There will be glorious failures and successes along the way, but those will be our expressions and our learning opportunities. If we also curate our back catalogue, by which I mean actually go back and look at our “keepers” critically and with a fresh eye, then post production also provides us with opportunities to craft new work from old. Over time tastes, techniques and skills change and grow and we have a useful basis to go back and re-work some things.

 

You can do this now. Go back, pick a frame from, say two years ago (you really must get round to freeing up that disk space), and rework it. Better yet randomise your choice. You do not, absolutely do not, have to have advanced photo-shop skills to do this. Use something like Google’s Picasa, re-crop, play with the shadows and highlights, darken/brighten it, apply some of the filters, and start to think what it is you like/don’t like. Find some ready-made effects on the internet or in editing programmes like Smart Photo Editor or, as Mac used, Topaz. Just, if it’s a treasured possession, make sure that you are working on a copy. We will revisit looking at photos critically and how to use the results later on in the season, the blog has been there before, but there is a lot to be learned from just messing about with what you already have from time to time. It’s not just a walk down memory lane we are talking about here, we are also talking about the opportunity to use editing software (including the Adobe Suite, Gimp and the other “Grown up” editors), to actually learn and develop from a historical, personal perspective by looking at how our style, techniques and competencies have evolved.

 

Back on the camera there are other perimeters besides the exposure triangle and filters and presets that can be employed. Techniques such as free-lensing a.k.a lens whacking, DIY Macro, or just exploring the in camera effects, for instance help to mix it up. That, I guess is really the basis of Mac’s message. You already have a catalogue of images, go back and have a look at them, they represent an opportunity to educate yourself using your own materials. And maybe even make a better go of it? Mix it up helps you to not keep taking the same sort of photograph each time you take the camera out, or helps you take the same sort of photograph differently because you have a better idea of what you want to see in the finished image, thereby giving you the chance to control the important elements to that vision. You get more of it right in the camera. In Stephen Covey’s best seller “Seven Habits of Highly Effective People” one of those habits is to “Start with the end in mind“. Sound advice because it also helps with those days when nothing seems to work and you end up pointing and shooting in that hit and hope manner (had one of those yesterday at Woodhenge), because I didn’t really know what I wanted to show. What I did think I wanted was a drone but that’s not in my price bracket. What I should have done is concentrate on details, probably very small ones in what is a big landscape. Still, live and learn. So, thank you Mac Bouchere, lots to think about.

 

 

N E X T   M E E T I N G

 

Mini groups presentations.

6th August 2015 – Bath Stone, Back Button Focusing and Exposure Lock

You cannot deny the poetry of Bath stone in a soft sunset, with the canal and the river yielding mirrored Georgian realities on a pleasantly warm and breeze-less evening. At least until you get home and look at your images to finally yield to the notion “What the hell was I thinking?”. Last minute change of venue with the Bristol International Balloon Fiesta closing roads around the intended destination of Leigh Woods, and a fine suggestion from Vice Chair Myk Garton saw us decamp the dozen miles or so to the World Heritage City of Bath. Two topics left over from last week to discuss this: back button focusing and exposure lock, both of which were useful tools on the night.

 

There are two buttons on the back of most DSLR/CSC’s from the hobbyist models upwards that are rarely if ever troubled by the majority  of hobbyist photographers. One is the “Back Button” AF and the other the AEL (which may be represented on your camera by a star or asterisk). Both are incredibly useful and are really worth cultivating as default, in the case of the back button AF, and useful tool in the case of AEL, that can help increase your number of keepers. A little bit of background is useful in understanding both.

 

Back Button Focusing (refer to your manual for the native translation in your Camera’s Brand-Speak) does exactly what it says on the incredibly expensive magnesium alloy tin, or plastic camera body as befits your pockets/needs/delusions of grandeur. It is a button on the back of your camera body that activates the camera’s focusing system in isolation from the shutter release.  When you operate via the shutter release a half pressure triggers the autofocusing system (assuming you are not mounting  a manual lens) and a full depress activates the shutter release. Usually the shutter will not fire until the camera processor detects all the algorithms are in place to produce a point of focus and an acceptable circle of confusion (i.e. something is in focus as we discussed last week).  The button itself is usually marked AF or a version thereof and is normally accessible with the right thumb (I’ve never seen one on the left but then I haven’t conducted a survey in any depth). And it’s on the back of the camera.

 

So far so blindingly obvious. Also, so what? Well, my skeptical friend, for that we shall have to take a brief incursion into the Trinity of Focus you played with once, got annoyed with then left on single shot. That, incidentally, is a perfectly acceptable solution because it’s your picture, your way. You want to do it the hard way, then suffer on for your art. It will not take better pictures, only you can do that, but it will help you be prepared for those better pictures, if only by speeding the whole process up and in more than one way. It is a little like buying a fully spec’d DSLR and leaving it permanently on auto or programme. In one way an expensive choice, but if you know what it does in those modes and you know how to override it in the situations where you think you need to push something to get the effect you want, then, pilgrim, it’s not such an expensive choice. It’s one that is made with a purpose rather than one made unthinkingly.

 

There are in our CSC/DSLR and some bridge cameras usually three flavours of autofocus. They may have slightly different sets of initials and names but they will be essentially the same. They will be in the menu system and may be programmable, at least the menu access may be programmable, to a button on the camera body.  RTM (Refer To Manual). The auto focus programmes in your camera were designed because your subject is doing one of three things. It is either static or it is moving. Or you are. Or you both are.  The important dynamic is that between the subject and the sensor.  What the back button does for us is allow us to switch between modes as required without having to resort to the menu system.

 

So, lets take the modes in alphabetical order, starting with AF-A. -A is where the camera decides, as is the case with all auto and programme modes, and it chooses between the other two modes depending upon what is closest to the idea set by its algorithms, i.e. is the subject static or moving relative to the sensor.  On modern cameras it is pretty good but it only responds to what is, it won’t anticipate your next move, so it will always be playing catch up. -C is continuous. When the subject is moving the focus moves.  -S is for when the subject is still, like a portrait. What the back button does is take a step out of the process of firing the shutter, the focus (at half way down)  is done by the back button and so the shutter button becomes just that. Without disabling the focus step the lens will attempt to refocus that which is in focus (which you have already framed as part of your composition). Doing things twice, slows things down. You are effectively switching between –A and –C at a press of a button. There is always manual focus of course, but this tends to be easier with manual lenses which have a longer throw (the barrel twists further because they are geared lower to make them easier to focus by hand) and no where near as rapid.  In the words of Professor Fate, “Push the button, Max“.

 

We’ve talked about exposure before and its relation to colour saturation, detail contrast and so on so I won’t go over that in this blog.  I want to concentrate on an option rather than an effect, though the two are linked, of course. The exposure lock button found on most DSLR/CSC cameras and some bridge cameras. Sometimes the exposure you need is not the one your camera is showing you.  This can be down to the metering mode you are using and the fact that it is metering an average from the area you have selected to measure from in terms of both the subject and the percentage of the sensor coverage involved.  There will be a wide, centre weighted and a spot option. Wide is usually factory default. Spot takes a very small area in the middle.

 

Essentially, in tricky lighting situations, probably but not exclusively covering a wide variation, you meter from the most important part of the scene to your image, keep the AEL AFL or * button depressed then recompose and take your image. The overall exposure will be governed by that part you selected. You don’t have to use spot to do this, just influence that part of the scene you want to feature to your satisfaction (this is far, far easier on a CSC/DSLT where what you see is what you get or in your live view if it allows composition other than pure review).  It is very effective and can be used with ISO compensation for fine control. On our Bath perambulation it was very useful when we were presented with a glorious sun set and allowed for much of the foreground to be silhouetted whilst retaining the exposure for the sky. Yes this could have been done in manual, but it was done far quicker using Aperture Priority and AEL. Try it, it is surprising useful.

 

Next week a change in programme where Nick Hartley has negotiated access to the Tannery where he works. Details on Facebook and the club Flickr page as numbers are limited. If your name’s not on the list your not coming in. Who’d a thought leather had a door policy?