Photographing a dark subject on a dark background

After last week’s post on photographing white subjects on white background it’s only natural to talk about the exact opposite and photograph something black on a black background.

If you remember to photograph a white scene we basically set our exposure to about 2 stops brighter than the camera tells us and everything worked out, so you may expect that for a black scene you just set your exposure to about 2 stops darker and call it a day – but things are not that simple (if they were this would have been a very short post).

The first problem is that black on black will result in a image that is, well, black – we get a picture where it’s actually difficult to see the subject and when we scale the picture down it can become a completely black box with no visible details, in the white on white picture we had shadows that defined the shape of the white objects here the shadow doesn’t help us because it’s also black.

So if we want people to be able to see what we are photographing we really want to keep the subject almost black and make the background gray.

Than we get to the technical problems, when everything the camera sees is black there is very little light getting into the camera – this means this is going to be a long exposure and you need a tripod, it also means auto focus is going to be slow if you can auto focus at all and that you really want a camera with an optical viewfinder (your camera’s screen or an electronic viewfinder are going to be completely black).

Also, if you use a DSLR light coming in trough the view finder can completely mess up the camera’s light meter (because there’s much more light in the room then is reflected into the lens) so make sure to have your eye on the viewfinder or at least cover it with something.

Black surfaces also tend to be reflective, but that’s a different problem we’ll talk about on another post, so I’ve selected non-reflective subject and background for this post – a camera lens on a fabric background.

So, first let’s see how the camera is doing without our help – I’ve put the camera on a tripod with a remote shutter release, switched to Av mode and selected F/11 as the aperture because I want the entire lens to be in focus in focus (I was very close and F/11 gave me just under 9cm, or about 3.5 inches of focus) – this gave me a 13 (!!!) seconds exposure at ISO 400 according to the camera’s light meter and resulted in this image:

You can easily see the picture is both way too bright and way too pink, the brightness we expected but where did all this pink come from? to keep this a low budget production (I expect my readers are not pros with easy access to studio equipment) I’ve use a black T shirt as the background and while that shirt looks completely black it actually reflects much more red light then blue or green – especially with such a long exposure.

Let’s look at the histogram:

You can see the image is very bright with almost the entire image in the right side of the histogram, you can also easily see the picture is not as color neutral as we expect from a mostly black image with a little too much green and way too much red (you can also see by the small bump at the far right we have some over exposure, this is the light reflection on the top of the lens).

So, how do we know what’s the right settings for really nice black? the camera’s LCD screen does not help us here (since. like we said in last week’s post it’s brightness is way too inaccurate) and it’s hard to judge the difference between “nice rich black” and “way too dark” by the histogram – so I took 15 pictures at a third of a stop difference starting at the camera’s exposure and ending when the picture was very obviously under exposed and then checked the results on the computer (this is called “bracketing” taking multiple photos around what you think are the correct settings to make sure you get a good one).

For you enjoyment here is a composite of the center part of all those images:

The best image was the one exactly two stops darker than the camera’s meter (how wonderful – this is what was supposed to happen), and here is that photo:

And it’s histogram:

Now all that’s left to take care of is that horrible pink color, obviously the best solution would have been not to use a fabric with a red color cast to begin with – but I’ve decided to fix it in post processing instead, I’ve loaded the out of camera JPEG in the free paint.net and adjusted the color channels in the “Levels” window, I’ve then done another quick levels adjustment on the reflection in the top of the lens and got:

And the histogram:

Obviously I could get a better result if I used the raw file and loaded it into Adobe Photoshop or Lightroom – but I wanted to show you what can be done with two minutes and free software.

 

That’s all for today, next week we’ll take a break from black and white subjects and look at something else.

Photographing a white subject on a white background

The light metering in modern cameras is great and in most cases the camera’s automatic (or semi automatic) modes do a good job at setting exposure – but the camera sets exposure based on the assumption that whatever you are photographing is of average brightness (about 18%, if you care about the technical details), this works great for average scenes but fails miserable for scenes that are mostly bright or dark.

The stereotypical examples for photographs that are white are snow and brides but since I don’t have either of those here I’m going to photograph milk – a bowl of white milk on a white plate on a white tablecloth.

I’ve put my camera on a tripod, attached my 50mm lens, switched the camera to Av mode (A on some brands), set the aperture to f/3.2 for a shallow depth of field and let the camera work it’s magic:

This image actually looked pretty good on the camera’s screen and I could only see how dark it is on my computer screen – that’s why you can’t trust your camera’s screen to judge exposure and you have to look at the histogram, the histogram is a graph that shows you the brightness of the image, there’s almost t always a way to view the histogram in the camera when you preview the photo, here is the histogram for this picture:

See that bump in the middle? that means that most of the image brightness is almost in the middle, that would be fine for most images but with all that white we want this picture to be much brighter.

So what do we do? we actually have two solutions to this problem:

The Good – Exposure Compensation

Your camera has something called “exposure compensation” – it’s a way to tell the camera “do what you meant to do just do it X stops brighter/darker”.

If you want something to look white but not be over exposed it should be about 2 stops brighter than average, for the following photo I’ve set exposure compensation to +1 and two thirds:

This image actually looks too bright in the camera preview – just to remind us we can’t use the camera preview to judge exposure, and the histogram for this image:

See the big bump on the right? that means most of the pixels in the image are very bright and the fact the bump doesn’t touch the right edge means we haven’t over exposed the image – perfect.

The Better – Manual Mode

Using exposure compensation is good but there’s an even better way – use manual mode, yes the big scary manual mode, it’s actually easy in this case.

To set your exposure in manual mode just zoom in (or get close) so your camera only sees white, set you camera to one of the semi-automatic modes and set your expose compensation, now take a test shoot and check the histogram, if you are happy with the results just switch to manual mode and set the same values the camera used.

So why use manual mode if you use the same settings as in the auto mode? because now the settings won’t change if the white animal you are photographing jumps in front of a dark rock or if the bride dressed all in white is joined by a groom in a black suite.

Let’s take our milk image in manual mode:

And now add something big and black just to fool the camera’s light meter:

See how the white milk keeps the exact same color between images?

You can see the black hat is actually seriously underexposed but I don’t care because the white milk is my subject – and in manual mode the camera doesn’t try to second guess me and compensate – keeping details in both the whites and the blacks is a topic for another day.

 

Hope you enjoyed this tutorial, now it’s time to use our setup to eat breakfast.

Making the Background Black

Last week I’ve posted about how to make the background white, this week we’ll go the other way and make the background black, the doll in the picture to the right was shoot in exactly the same location as the white background shoot from last week, the wall behind the doll is off-white in reality.

As with white background the trick is that the camera is limited in the range of brightness it can capture, go above that range and you get pure white, go below and you get pure black. Also, again like width the white background, the distance between the subject and background is critical – the longer that distance is the easier it is to get the background to turn black.

The trick is very simple. you set your flash to low power and get it as close as possible to the subject – and than because the distance from flash to background is relatively much more than the distance from flash to subject the background gets very little light compared to the subject and since we used a weak flash to begin with that light is not enough for the background to even appear in the picture.

Now, since my “studio” is a tiny room I couldn’t  get the required distance to get the background to turn black in-camera – so I’ll show you how the get an almost black background in-camera and then finish the effect with less than a minute of post processing.

I shot this in exactly the same place as last week’s white background pictures, our model for today is an hello kitty doll (because it is brightly colored and will look good against the black background), I’ve also covered the glass we used in the white background picture with something black (the back of the same picture frame I took the glass from).

First set you camera to manual (M) mode, your shutter speed to your camera’s sync speed, your ISO to the lowest value and your aperture to something small, F/11 is a good starting point – you want a setting that will produce completely black image if used without a flash.

Now for the flash, you want to flash as close to the subject as possible without it showing in the picture, you also want to control the light, in this case I’ve used a DIY softbox (take a cardboard box, cut and glue to make a funnel shape where the small side is the size of your flash head, cover inside with aluminum foil, cover large opening with something white that is not completely opaque, I used a diaper) and I’ve also placed some black packing material on the far side of the softbox to block the light from hitting the background (something that blocks the light from going where it shouldn’t is usually called a flag).

Here’s how it looked from above:

You can clearly see the cardboard softbox, the flash is below the cardboard flap at the back of the softbox, you can also see the flag and on the other side you can see a folder silver car windshield cover (I’m not sure what those things are called), in this picture it is used as a reflector, bouncing light back to our “model” so that the right side of the doll won’t be in complete darkness.

Now I’ve played with the aperture and flash power to get a good exposure of the doll without getting any light on the far wall – and, as I said before I couldn’t do it – so I’ve taken a picture where the background is almost black and the doll is a little too dark (but don’t worry, we will solve this problem in a minute) the somewhat disappointing photo is (click to see larger version):

You can’t really see it but the background in this picture is actually not completely black, if we increase the brightness of the picture the background will appear – but this can easily be solved by the levels or curves tool of your favorite graphics package, because we are doing a low budget photo shoot I’m going to show you how to fix the problem in two ways using two free software programs:

In paint.net I’ve used the levels tool, I’ve pulled the lower handle on the input slider just a bit to make the background really turn black and than pulled the middle handle on the output slider a lot to brighten the doll.

In GIMP I couldn’t get the result I wanted using the levels tool so I’ve used curves instead, I’ve kept the far left of the curve at zero to turn the background black and raised the rest of the curve to brighten the doll, I had to fine tone the curve a bit so I don’t lose details in the white parts.

Here are the results from the two programs with the settings I’ve used:

Adjust

You can see there are some visible reflections in the black paper thing the doll is sitting on (it’s most visible in the middle paint.net version), but those are easy to edit out – just paint over them with black.

And the final result is (click for larger version):

And that’s how to get the background to turn black for product photographs, hope you enjoyed this tutorial.

Making the Background White

In this post we will see how we can get completely white background for product photography with just one flash.

The mouse picture was shot is JPEG, it has been cropped, resized and sharpened but I didn’t do anything in post to make the background white – so how do we get that white background?

The trick is extremely simple, the camera can only capture a very limited range of light intensity, we can move that range up to capture pictures of bright subjects or down to capture pictures of dark subjects but at the end we are limited by that range – anything brighter than the top of the range will become pure white (known as “blown highlights”) and anything darker than the bottom of the range will become pure black (“blocked shadows”).

Having blown highlights or blocked shadows unintentionally in the picture is considered a bad thing – but if we know about them and control them we can use them for our advantage.

In this post we will see how we can get white background, next week we will look at getting black background.

The first thing we need is space, light power falls off very quickly when we get farther from the light source – so if we can get some distance between our subject and the background we can more easily control the brightness of each of them individually.

Our model for today is s small green dinosaur, the dinosaur is standing on a piece of clear glass (actually some kind of plastic) I took out of a cheap picture frame, the glass is wedged into the space between two drawers so it’s suspended in the air.

Now we are ready to shoot the dinosaur (without flash – because we will use the flash later to light the background), for this we don’t even need to use manual mode, I’ve set the camera to Av mode (because that’s how I like to shoot) put the camera on a tripod (because I want to use lower ISO and longer shutter speed) and aim it at the dinosaur.

This is the photo I get:

Now it’s time to add flash, the flash is set to manual mode, connected to a cheap radio trigger and aimed at the wall behind the dinosaur, we want to set the flash to the lowest power level that will give us the white background – we want it bright enough to completely turn the background white but we don’t want light from the flash bouncing around and lighting our subject.

For this particular flash at this particular situation it was 1/64 of full power – I’ve got there by setting the flash to the lowest power and taking test shoots every time trying a slightly higher power level until I got to the level that burned the background (hint: the camera LCD screen is very bad for checking brightness but most cameras have a feature you can turn on that will make blown highlights blink).

Here is what the setup looked like, note the flash on the floor (because I didn’t have anything to put it on) pointed at the wall – sorry about the image quality, this picture was taken with my phone:

And this gets us this photo:

You can see that the near edge of the glass and the drawer holding our set are visible – but we don’t care because a simple crop will give us:

 

And that’s it, hope you found this useful, next week we’ll talk about making the background black.

The Exposure Triangle

There are 3 factors that control the amount of light that enters your camera: Aperture, Shutter Speed and ISO. Those factors are called the exposure triangle.

My favorite metaphor for the exposure triangle is that taking a picture is like filling a bucket with water, to get the correct exposure you need to get the right amount of light into the camera (or water into the bucket), to control the amount of water you can keep the water flowing for shorter or longer amount of time (shutter speed), use a ticker or thinner water pipe (aperture) or replace the bucket with a smaller or larger bucket (ISO speed).

It’s worth noting that the exposure triangle has nothing to do with the triangle shape we all know and love, but “exposure triangle” is a catchy name (better than the more geometrily correct exposure cuboid).

Changing the amount of light with any one of the 3 factors will give the same brightness as changing the same amount with any other factor – but not the same image because aperture also affects depth of field (among other things), shutter speed controls how you capture motion and ISO changed the amount of digital noise in the image.

To demonstrate this I’ve set the camera on a tripod in front of a toy microphone, set it to manual exposure and manual focus, and I’ve also set the white balance (because auto white balance can change white balance between pictures)  – and took 13 photos , 1 correctly exposed according to the camera light meter and then for each of the 3 factors I took 4 pictures at +2, +1, –1 and –2 stops from the correct exposure.

I took the JPEG images right out of camera and combined them into the table below to show that the brightness really does change by the same amount.

Combined

The darker band on the right side of the pictures is actually the corner of the room.

You can’t see the changes in depth of field or noise in those small images but that’s ok because you also can’t see them in the full size, the maximum aperture is small enough to get the entire microphone in focus and the background is a solid color – so no visible change in depth of field, also, there is plenty of light and my camera has good high-ISO performance so there’s no visible noise in the high ISO images.

Also, the “correct exposure” picture is too dark and the over-exposed pictures are better – this is because the light background fooled the camera, exactly why this happened and how to deal with this will be the topic of a future post.

Understanding f Numbers

In photography the size of the aperture is measured in f numbers, a lot of people just learning photography find f numbers confusing, this starts with them being backwards (smaller aperture = larger number) and continues with the fact that to double the amount of light you multiply the number by 1.4.

The aperture has a huge impart on the photo you make, so being confused about it is not a good thing.

Basically it’s rather simple, an aperture of f/2 (for example) means the width of the hole in the lens is the focal length divided by 2 (and f/8 is divided by 8, f/2.8 is divided by 2.8, etc.) so if you have a 50mm lens at f/2 the width of the hole in the lens is 25mm – it’s even written as a math equation.

Now the reason for the numbers being backwards is obvious, dividing by larger numbers give smaller sizes.

The reason for multiplying by 1.4 now also becomes simple – you just take the formula for the area of a circle and you get that to make the area twice as large you have to increase the diameter by the square root of 2 (or approximately 1.414) – I’ll skip the math, you can easily check this for yourself if you want.

Now the only question left is – why do we specify the aperture size in relative terms? and to answer that I took a few pictures, both pictures were taken with the Canon EFS 18-135 f/3.5-5.6 IS using the same camera settings (ISO 100 f/7.1 1/160sec) from the same location – the only thing that changed between pictures was the focal length (I zoomed in and out) – the first picture was taken at 18mm and the second at 135mm:

And for you convenience I’ve cropped the 18mm photo to show the same area as the 135mm photo:

Apart from the effect of the focal length on depth of field (that’s the topic of a different future post) both images look the same, if you look closely at the middle flower you will see the same colors and the same exposure in both pictures.

But the diameter of the hole in the lens is 18/7.1 = 2.5mm for the first picture and 135/7.1 = 19mm for the second – a 7x difference! and yet they both let the same amount of light into the camera – and that’s why we measure aperture in f numbers – if we used the size of the aperture the exposure would have changed radically when zooming in or out.

And, as a side note, it’s now also easy to see why cheaper lenses have variable max aperture – the same size hole has different f numbers at different focal lengths, and making a lens that can open up at the same ratio at both ends for a large zoom range requires a very big lens (or a tiny aperture at the wide end).

Creating Motion Blur

Motion blur is created when the shutter is open long enough for the subject to move – not very complicated.

Unsurprisingly you control motion blur by changing the shutter speed, first a little experiment to show the effect of shutter speed on motion blur – and then we’ll add some flash magic to make the photos more interesting.

To demonstrate this I needed something that moves in a constant speed so I’ve used a small spring-loaded toy, the camera is on a tripod and pre-focused, the train moves at exactly the same speed in all pictures and I’ve pressed the shutter when the train reached the same location (more or less).

Because I didn’t want to change depth of field the aperture is the same in all pictures (f/5) , I’ve shoot those pictures in Av mode, I’ve manually set the aperture and ISO and let the camera calculate the shutter speed, all pictures are strait out of camera with no processing (except for reducing the size so they fits here).

The settings described below are for example only, the required shutter speed depends on the speed of the subject – and unless you are photographing the same spring loaded toy train I did you will need to adjust.

We start at f/5 1/100sec ISO6400 – the picture is very noisy due to low light/high ISO but there is very little motion blur.

At f/5 1/50sec ISO3200 (look at how halving the ISO exactly doubles the shutter speed) there’s enough motion blur to be really noticeable but not enough to look like we did it on purpose.

At f/5 1/25sec ISO1600 there’s significant motion blur.

At f/5 1/13sec ISO800 the train is so blurry it’s becoming unrecognizable.

Everything continues at 1/6sec ISO400 and 0.3sec ISO200

And finally at f/5 0.6sec ISO100 the train disappeared and all we are left with is some blur

The kind of blur we’ve seen so far actually doesn’t feel like motion, it’s just too blurred – but there’s a very nice technique that turns the picture above into this:

This picture was taken with the same camera settings as the previous one (Av mode, f/5, ISO100, same location and light) but with an added flash, I’ve used the camera’s pop up flash, with flash exposure compensation dialed down all the way to –2 stops (because a direct on-camera flash would slightly over expose the train and background resulting in washed up colors and the unnatural hard shadows pop up flashes are famous for).

What happens is that we get the same blur we got before – and then the flash fires and we get a clear sharp image of the subject at the time the flash fired.

It’s important to note the flash is set to rear curtain sync (or 2nd curtain sync) – in this mode the flash fires at the end of the process right before the shutter closes instead of at the beginning right after the shutter opens, if we didn’t set the flash to rear curtain sync the blur would have been in front of the train instead of behind it.

Aperture

Aperture is the physical hole in the lens, changing the aperture opens and closes the hole in the lens, in the picture on the right you can see the hole and the “blades” around it that are used to make it smaller or bigger.

The Aperture size is measured in a unit called f number – a larger f number means smaller aperture (large number = smaller hole – yes, it’s reverse, but that’s how this is measured). On most DSLR cameras each “click” of the aperture wheel is 1/3 stop – so 3 clicks will double or halve the light coming into the camera (depending on the direction you turn the wheel, obviously)

The most important effect of the aperture is the bigger the hole in the lens the more light comes in – and wen more light come in we either get a brighter picture or we can compensate by changing the shutter speed or ISO – for example  by changing the aperture from f/8 to f/5.6 (3 clicks) we double the amount of light coming in – so we can compensate by halving the shutter speed, so if I go shooting handheld with my 50mm lens in f/8 and the camera tells me I need a shutter speed of 1/40 – at that shutter speed it’s really difficult to take a good picture handheld and it’s very likely I’ll get a blurry picture – but changing the aperture to f/5.6 will get me a shutter speed of 1/80 – in that settings it’s pretty easy to shoot handheld with a 50mm lens.

Quick tip – the aperture and shutter speed camera controls are usually set in the same increments so a single aperture “click” change the exposure by exactly the same amount as a single shutter speed “click”.

Aperture also controls the “depth of field” (background blur) of the picture, larger aperture (smaller f number) means shallower depth of field (less in focus and more background blur), let’s demonstrate this with some pictures.

Nothing says aperture like a stuffed lion toy  – so I’ve placed a toy lion on top of a trampoline (really) balanced on a plastic slide in front of a bamboo fence, I’ve put the camera (Canon 550D/T2i) with a 50mm f/1.8 II lens on a tripod, focused on the lion eyes and set the camera to manual focus, the white balance is set to daylight and the pictures ware taken during sunset with the sun behind the camera, I was pretty close to the lion because I wanted a very shallow depth of field in order to exaggerate the aperture effects), the pictures were taken on Av mode.

Here are the pictures, almost strait out of camera with no post processing what so ever (the pictures on this page are scaled down, click on the picture to see a bigger version that much larger but also scaled down a bit):

The first picture (right) is at f/1.8 1/100sec ISO200, the lions nose is super-sharp, the eyes are a little soft (you can see it in the full size version – I probably accidently bumped the tripod a little and moved the focus from the eyes to the nose – the depth of field is so shallow with the lens wide open) the ears are obviously out of focus even in the scaled down web version and the background is a nice undefined wavy pattern.

In the second picture (center) I stopped down to f/2.5 (1/50 ISO200), the eyes are not as soft as the f/1.8 version but still out of focus.

In the next picture (right) at f/3.5 1/20sec ISO200 the eyes are finally fully in focus, the ears are still clearly out of focus, the background is completely blurred but you can already guess it’s a bamboo fence.

Stopping down again we get to f/5 (1/10sec ISO200) on the left and then to f/7.1 at 1/2sec on the center. On the right at f/10 0.4sec ISO200 the downscaled version is already sharp with maybe just a tiny amount little blur in the background, in the full size you can see the background is still blurred (pictures become sharper when you scale them down) but the entire lion in completely in focus.

The background continues to get more details at f/13 0.6sec (left) and the last picture I took is at f/20 1.6 seconds (still ISO 200, on the right).

We clearly see that increasing the f number (or closing the aperture, also know as “stopping down”) – increases the depth of field, in each picture more of the lion is in focus and the background becomes more defined.

And we also clearly see that id we get the depth of field too shallow we take the risk of missing our focus – and your model might not be very happy you’ve chosen the tip of her or his nose as the focal point of the photo.

There’s another effect of the aperture size I want to talk about quickly – with large aperture (small f number) lights seem to glow, with small aperture (large f number) they become star shaped, I’ve taken some photographs of the lights above a highway near my home to demonstrate this.

This time I used my EFS 18-135mm f/3.5-5.6 IS lens, again the camera was on a tripod and the white balance was set to daylight (I had no idea what’s the color of the lights and didn’t care if the colors are off as long as they are consistent – but I’m happy with the results) the pictures were taken at night the lens was zoomed all the way to 135mm and on manual focus, the pictures were taken on M mode.

Here’s a picture with the aperture wide open at f/5.6 1/20sec ISO200 – you can see the strong round-ish glow around each lamp and the huge halo around the entire thing (I really love the “molten metal” look of the pole)

Here’s another picture of the same lights with the lens stopped down to a ridicules f/36 with 1 second exposure at ISO 100, now the big halo is gone and each light has a very nice “starburst” effect – in this experiment I didn’t keep the exposure constant between pictures if you do the math you can see I’ve closed the aperture by 5 and a third stops, lowered the ISO by one stop and reduced the shutter speed by 4 and a third stops – resulting in a two stop difference between the two shots (or in another words, the second picture has only one quarter of the light in the first picture)

And finally, if we combine both settings by opening the aperture to f/5.6 and setting the long 1 second shutter speed (at ISO 100) it looks like our street light is now powered by a thermonuclear device (this is 5 and a third stops brighter the previous photo – or approximately x39 the amount of light)

New blog – new beginning

A few month back I’ve got a new DSLR – and with this new camera came a renewed interest in photography.

After spending a lot of time on-line reading everything I can about the subject I’ve decided to open this blog.

I’m going to use this blog to improve my own photography by explaining various tips and techniques (teaching is supposed to be the best way to learn) – and I hope other people will also find it useful.

The blog name is “Useful Photo Tips” so I’m going to keep the post focused on useful tips and techniques, I’m going to skim the (very important) theory behind whatever I’m explaining and focus on how to actually make it work – with lots and lots of examples.

This should be fun.