Tagged: centre

18th January 2018 – Keynsham Photographic Centre Come A Visitin’

A most compelling evening (well if you are a camera club member) had courtesy of Keynsham Photographic Centre. Simon and Neil took us through papers, sizes and types of processes KPC offer and their knowledge and enthusiasm went a long way to explaining why KPC is a destination of choice of so many serious photographers here-abouts. Around 2 in 3 of those present were already users but we all had something new to learn about the services they offer, which are quite extensive. I have always found them to be helpful and friendly and I am happy to pass on a recommendation to use them.

 

Why print? There is an emotional and a logical answer to this. The emotional one is that we do seem to react differently to a print than to a projected image or one on a phone or other screen. This is certainly the case with the written word. With pictures it might be an age thing, with those of us of a certain maturity having an emotional tie to what we started with, the family albums and so on, but as these are family history it is not uncertain that these emotions are passed on. It might be the way we view what is art. Even slides are, these days, often rendered digital. Prints have a longevity that digital files cannot match.

 

The logical one is more existential. Our photographs aren’t photographs until they are printed. They are computer files that are capable of being rendered as images given the right, seldom very cheap, equipment. To that extent they are, at best, semi permanent records. They exist not as pictures but as 1’s and 0’s and that makes them vulnerable to damage, loss and redundancy in many different ways.

 

One of the questions that came up in discussions was the notion of the minimum resolution (pixels per inch or PPI) as a ratio to print size that is compatible with a reasonable quality print. In order to look at this we need to look at and differentiate between two measurements that the computer file we turn into a picture holds – and which can be reset via (photo editing) software. The first is Pixels Per Inch and the second is Dots Per Inch, or as we will refer to them PPI and DPI.

 

There is a previous post dedicated to this and a good start if your interest is more than passing. Essentially the PPI is a measure of the resolution of the computer file when shown on a screen and the DPI a measure of the resolution that a printer will reproduce the computer file as a digital print. They are not the same thing, they are not interchangeable, the connection between them is that you cannot use DPI to overcome low resolution in the PPI. That might not seem like much of a connection but it is a common error, at least it is a common misunderstanding.

 

Just as one is not strictly reliant on another there is an optimum setting for both, but it is not a single magic number or formula. This is because different manufacturers of camera sensors and printers construct their wares in slightly different ways to slightly different priorities. The only rock solid constant you can apply is garbage in garbage out aka GIGO. What doesn’t help is that there are always going to be subjective elements to the ideas of output and acceptable, but we can set these aside.

 

A slight diversion, but one that is worth taking, is the purpose for which we are taking our images in the first place. The digital age has brought with it a number of outlets that, even 20 years ago, were pipedreams or even unimaginable to most photographers. Film cameras would enjoy their predominance for another 10 years in the “serious” and professional markets. A decent living could still be made from stock photography. These days there are far more outlets and they demand different things of the data files they publish. What remains is the fact that proper prior planning prevents poor photography. Start with the end in mind and choose formats etc accordingly.

 

The argument for recording images in camera RAW is that all the information is left in. The argument for JPEG is its universality and space saving compression. The fact is you can shoot in both and convert your final image from RAW to JPEG or any other format (has to be some other format as you cannot save in RAW). In your final version of the image is the information that other devices are going to use to present your image, including colour space, PPI and a whole lot else. The point here is that you are going to have to make, or let programme defaults make, these decisions to determine the look of your output (as best you can).

 

So, long way round to the answer we were looking for but the fact remains, that for all the reasons above, there simply is no answer to the question of a ratio of file resolution to print size because Pixels are not the same size on all cameras – 24 mega pixels on a 35mm sized sensor take up more space than 24 mega pixels on an APSC sensor. There are approximations, guidelines and above all, experience. Let’s look at rules of thumb, but first a caveat.

 

Pixel peaking, the urge to zoom to the maximum and suck the teeth at the lack of relative clarity, is neither helpful nor useful, outside of certain photographic publications desperate for some comparators in a world where you really have to go some to find a “bad” lens or sensor. It’s the aggregate of the pixels used that we view and a badly composed photograph is a badly composed photograph regardless of the amount of money you have spent or your equipment’s DXO rating. We are here looking at making a print of what you have got, regardless of your motive to print it.

 

Lets first talk of PPI. Smaller sized prints, say up to 10 x 8 (ish) we can get a reasonable print at 125 ppi. That is to say at arm’s length it’s going to look OK. Press your nose against it or use a magnifying glass it is going to look pretty rubbish. I have to say that such a view point rather spoils the whole point as, again you are looking at the aggregate of the pixels after all, or as I like to call it, “The picture”. This is a fall-back position only, If your default is 72ppi (i.e. it’s designed to show up on your computer or phone screen) then you are not going to get much above a 6 x 4, maybe 7 x 5 at a pinch, out of it (feel free to prove me wrong because you are only going to find out by using your  combination of equipment and the printer you choose). The best lies between 200 and 300 ppi, by more or less common agreement. KPC ask for 305 PPI. Basically of you use the 300 end of the range you are likely to be close to the optimum for most commercial printers at standard sizes. Refer to your supplier for the necessary information. To change images PPI we use editing software like Lightroom, Gimp or Affinity.

 

But we were looking for a rule of thumb. Any minimum figure is a result of the combination of equipment particulars and specifications and materials used.

 

So, take the longest edge of the image (measured in pixels) and divide by the longest edge of the desired print size (measured in inches). If an image measures 3,840 x 5,760 pixels and you want an 8 x 10 inch print. 5,760 pixels ÷ 10 inches = 576 ppi. That’s more than enough resolution. If you want make a 30 x 20 inch poster out of that image, you’d have a resolution of 192 ppi (5,760 ÷ 30), which isn’t high enough for optimum, if we are looking at least at 200 PPI.  This is a minimum remember, so adjust accordingly.

 

Alternatively, and my personal method,  size the image in inches at a ratio of 1:1. So an 18 x 12 print is sized as an 18 x 12 image in my editing software (Gimp). The resolution is set at 305 by 305 dots per inch as I use KPC, and the image, in pixels, is 5490 x 4118. The down side is the file size, the upside is its going to fit without faffing around.

 

So   http://www.keynshamphoto.co.uk/   and start printing!

10th November 2016 – Ann Cook and Carnivals

Anne Cook made a welcome return to Reflex with another illuminating talk that was, let’s face it, fun.  We can’t always locate the terms guest speaker and fun in the same sentence and whether we learn anything apart from the hardness of chairs that children are subjected to in modern day education (chairs, damn it, the cold hard floor was what we  got, etc etc) is not necessarily a topic we need to travel to club to speculate on.  The feedback from members was particularly effusive which is always a good sign.

 

Ann showed, amongst many other fine examples some images taken at carnival, which is particularly apposite to this time of year as we are coming to the end of the Somerset season. The last one on the Somerset circuit is at Wells this coming Friday (18th November 19:00 get there early). Having attended the Burnham-On-Sea round this year I can definitely affirm that it is something well worth making the time and effort, if you can get there.

 

So we are going to look at taking photo’s of street processions at night. The most obvious thing is that we are talking of photographing very high contrast scenes, that are moving, admittedly slowly, that  can look distinctly two dimensional as brilliant point of light swim through a sea of black, which generally require high ISO’s to get reasonable shutter speeds and some interesting metering challenges.

 

There will be the large floats, some a part of a two three or four articulated trailers, but there will also be smaller floats, hand carts and individuals decked out in lights, there will be groups and there will be all sorts of other wheeled and ambulatory traffic. Variety is not short at these affairs and the lights are the main attraction.

 

The basic answers to these conundrums is to crop tight, centre weight or spot meter and expose to the right.

 

Cropping tight means we are likely to even out the overall exposure in a reasonable amount of the frames we capture. We will still get areas of high contrast and some of them will still have totally blown out areas of white and areas of inky blackness, but there are a significant number where we can limit the dynamic range some. This can put more emphasis on the mid-tones but whether  that is a good or a bad thing is a matter of taste and of colour.

 

Metering these days is a lot smarter than it was five years ago. Leaving our camera on matrix / evaluative (basically our cameras approximation of the whole frame)  isn’t necessarily a disaster, modern algorithms are pretty good at drawing conclusions that prove to be reasonably “accurate” (they are accurate but that has to be measured against our expectations) but  we are talking an average balanced somewhere between the highest and the lowest value.  Most cameras have the opportunity to switch between two other modes that increasingly ignore larger parts of the scene.

 

This gives us more  information about a smaller part of the scene that we have judged to be more important. How do we know that? Well we’ve pointed our camera at it and taken notice of what effect this has had on our suggested exposure triangle settings. This is either  because the scales in our view finder for shutter/aperture or under or over exposure are indicating a problem or the scene in our EVF is too dark or too light. What the camera has done is taken all the zones programmed into it and set these against where we are focused to give the reading a final weighting. There are other considerations but these change form manufacturer to manufacturer and can incur consideration such as colour, highlights and so on – Nikon use a comparison data base of shots of similar light/shade characteristics. This is common to Evaluative and centre weighted modes.

 

More so than fancy names for “Taking-the-whole-frame-into-consideration”, centre weighted does what it says on the tin. It takes the information in the centre of the frame into account either severely downgrading or completely ignoring the information on the outside of the frame.  It doesn’t, by and large take notice of the focal point, instead just giving it a general, centre balanced reading. By restricting the area taken into consideration, prominence is given to the area more likely to include the crux of the image.  Good when the boarders contain light that is in strong contrast to the main subject and might otherwise have undue influence on the final decision.

 

Spot takes the central are only, around 2% of the frame, around the focus point. Everything else is ignored. Photographing wildlife or Super-moons (or just the plain old ordinary moon which in the carnival context is a lot more apposite) benefit from this. Taking the moon in particular, the difference is a blown out image using the evaluative or centre weighted options because the light reflected from the moon is many, many times stronger than that which might be bouncing around the rest of the atmosphere. The argument in the wildlife example stems from a similar situation, say in the question of a bird in flight where it will be darker than the sky it is set in, or for the variations between fur and the cover it is in or breaking from.  A characters face in comparative dark to the lights of a float with, potentially, tens of light bulbs throwing a shadow, yields a similar situation. Our meter might read the scene but in ways only remotely related to the way we see it.

 

Exposing to the right in itself gives no clear clue as to what exactly it is we are talking about. It relates to the histogram (posh name for graph) that we find somewhere in our camera’s menus and which we can turn on so that it appears in our camera’s live view and or view finder (depending on make and model). Pretty much every camera has the facility including some, but certainly not all, compacts and is also referred to as ETTR, even in polite company. The way the histogram is set out the shadows are on the left and the highlights are to the right. We don’t want spikes at the extremes of the scale because that tells us we are producing images that are heavily under or over exposed. Fine, but only to a degree, if we are shooting high key or low key portraits or similar.

 

What we want, in an ideal world is for there to be a fairly even shaped curve in between the two extremes of the histogram. That gives us an image that is evenly exposed. Of course this depends on the lighting of the scene and in extremes we know that shadows are more recoverable than burnt out highlights (if it is truly burnt out there is no useable information there to recover). Therefore we expose deliberately for the highlights in the picture and recover the shadows in post using whatever editing programme we have access to.

 

Of course it is a matter of personal preference, some people are dead set against the idea of ETTR, personally I find it useful, especially when someone else is controlling the lighting. In the studio we have more options and it entirely depends upon the sort of image we want to craft. The argument evolves around the number of tones on show in the image. If we are shooting a 12 bit RAW image we have 4096 tones available across the range. Each f-stop in our range (remember our meters render an average for the scene) accounts for twice as many tones as the previous one as our f-number increases. The brightest part of the range in the image accounts for half of the available tones, the next stop about half of that again and so on. The whole calculation takes place within the dynamic range of the camera sensor and that again is dependent upon make and model.

 

What happens is that by exposing to the right stretches out the details to the left and the more that happens the less smooth the transition between the dark tones, and we risk compromising the quality of the picture. That is why we need to look at taking pictures of the carnival floats in the context of the other two considerations we talked about above because the more we operate towards the centre of the cameras dynamic abilities the more leeway we have to accommodate the extremes of light and dark.

 

Go and enjoy.

 

N E X T   M E E T I N G

Kev Spiers and Rich Price on their return to Iceland.

August 2016 -New Season Approaches

Blog has taken a bit of a break these last three weeks – what do you mean you haven’t noticed? – so this week is a little bit of a digest of things that have crossed my viewfinder. Over this period the club has been up to Gloucester for a very pleasant evening and a model photo-shoot around the docks, Bath for stroll around the Royal Crescent and Severn Beach for the sunset. Our thanks also to models Ashleigh Claire, Keith Bristow, Carl Hawkins and Alice Jordan for their endurance and patience at the Gloucester Docks shoot, which from Facebook seems to have generated some interesting shots. Not quite as billed (the theme was originally going to be Victorian) but it was an entertaining evening nonetheless and we had the space largely to ourselves and another photographer and model who were doing a shoot. There was also an American car meet going on and all in all it was an interesting, if slightly humid couple of hours.

 

But the humidity of Glos. docks was nothing compared to a windless evening in Bath, which seemed to pile heat upon heat. Severn Beach was a little more civilised even if the evening did end in rain. The fact is we don’t very often get extreme weather in this part of the UK, for which we should be grateful, but still half a dozen people have lost their lives on the coasts around the UK in the last ten days or so. In fact the climate and geology of the UK is particularly stable yet still manages a huge variety of land, sea and urban views. But it’s not without its dangers.

 

One of those is people taking exception to you taking photographs. In this country the level of paranoia around children and photography is on the increase. I met with this some years ago – taking photographs of my own children. Now I am a reasonable man but telling me (wrongly) what I can and can’t do vìz a vìs the photographing of my own children in public, does rather try my patience. It always pays to be polite though and I am sure I was a lot more polite than I seem to remember being.

 

Scare stories are will always generate interest, trouble is when people act erroneously on them. And, of course, different countries different rules – over the weekend it has emerged that the “Burkini Beach” photographs of the armed French Police enforcing the law have led to the former Mayor threatening the prosecution of social media users sharing pictures of them doing so. Now the reasons for doing so are complicated and the reason for the Burkini ban is tied up to do with the 84 deaths on Bastille Day in the City of Nice, where the photos were taken. The point is, whatever you may think of these rules (a) ignorance is no defence and (b) your opinion of them does not change the law.

 

So, simply put, find out what these rules are before you take the camera out of its bag and stick with them. This Facebook Page is a good place to start.

 

On a more cheerful note the 2016-2017 season starts at the club on 1st September and we are kicking off with an event called my summer, where members bring in photographs they have taken over the summer and present them. That’s a sort of hint.

 

There is a lot on the programme again this year and we urge all members to participate as widely and as often as possible – it’s sort of the whole reason for the club after all. One issue that has arisen and needs addressing. The evenings where we use models on the basis that they get the images we take in return for their time do require that we honour our side of the bargain, whether we as individual photographers, think they are good enough or not. It doesn’t take much time and it is only fair. We can now use the photo entry system so that can be covered among its many other attributes, I believe, as it can be set up relatively easily, so no excuses really. Give up your best three (at least) and let the model worry about whether they are good enough or not.

 

We are fortunate in having such an active club but we also recognise and welcome new members. There has always been someone around to answer questions and there is quite a breadth and depth across the club and members always seem happy to give freely of their time. Long may it remain so. The programme for September includes: Photo’s we have taken over the summer break; Q and A session; A talk that looks distinctly chilly; and a photo mini marathon, ever popular. That is all in the next five weeks (photo-marathon and photo-marathon judging taking place in consecutive weeks).

 

So, what is your goal for this season? It’s always a good idea to have and we learn more when we have an idea of what success looks like. It might be to get yourself off auto/programme, not actually sins in themselves but the tool is making decisions for you creatively and artistically. There will be plenty of opportunities within the club schedule to practice that and to ask people about how they do it and why they do it that way. You might want to set yourself a one a day project over 7, 28 or 365 or some other number of days. Or take on some macro or portrait projects, the point is there are lots of opportunities and there is a lot of experience in the club, you can call on. Essentially next season is what you make of it, and the club is what you make of it, the opportunities are there for the taking.

 

Good luck!