Studio Flash

Turn a White Background Black

Turn a White Background Black

Really, Are You Having a Laugh??

I’ve watched several YouTube videos on taking pictures in adverse circumstances, including how to turn a white background black. Have you ever tried this yourself? It may not be as easy as you are made to think.

The Basic Principles

Turn White Background Black

Underexposing for Black..

In order to turn a properly exposed, non-clipping, bright white background to black it will need to be under-exposed. How much may depend on the contrast of the light used and the reflectivity of the surface, but is likely to be between 6-8 stops. In the example at left, the bright white, non-clipping exposure was 1/4s at f5.6 and ISO 400 whereas the dark exposure was 1/500s at f5.6 and ISO 400, some 7-stops less.

The chart at left shows the incremental reduction in exposure, one stop at a time, of a small white Lastolite reflector. Although, at a distance, a 5 stop reduction looks adequate, you can clearly see the reflector in the image on the computer.

The ambient exposure needs to be reduced substantially in camera, and the subject re-illuminated, to compensate for the reduction, usually with flash. Shooting in manual, most flashes have a range of 1 to 1/64 or 1/128 power (6 or 7 stops respectively). This may sound a little close for comfort (which it may be), especially when using light modifiers that reduce the flash by 2+ stops. You can also place the flash nearer to the subject if needs be however.

What Can Go Wrong?

When trying to turn a white background black, the re-illumination of the subject has to be specific to the subject. In other words, the 7 stops of flash that you add back in must not travel to the background and re-illuminate it as well! This is awkward in smaller studios (or a mostly white painted kitchen as in this case) where flash bounces round the room increasing the ambient again.

Mitigating The Re-Illumination Light Spill

There are two main ways of managing light spill, firstly to manage the direction of the subject re-illumination light (so that it misses the background) and secondly using the inverse square law in setting the flash to subject and subject to background distances. In the smaller studio it may also be necessary to mitigate bounced spill by using flags or black reflectors or covers.

Managing Light Direction and Spread

Two main strategies will help here. Firstly, avoid front lighting if you can because the spill will necessarily hit the background. Try and use side lighting or lighting from high up and to the side so that the spill-light travels past the side of the background or down to the ground. Secondly, use light modifiers to narrow the direction of light rather than having light going off in all directions. Choose your modifier based on the following priority list (worse to better) for best directionality.

  1. Shoot through umbrella
  2. Bare flash with wide spread
  3. Shoot back umbrella
  4. Bare flash with narrow spread
  5. Softbox
  6. Deep Softbox
  7. Softbox with grid
  8. Grid Spot
  9. Snoot

Finally, you may need to control spill by reducing reflections from large reflective surfaces. This can be achieved by using large black panel reflectors (or non-reflectors) or covering with black sheets or a roll of black paper. Obviously, if you have these to hand, I have to question why you are trying to turn a white background black in the first place!

Inverse Square Law

What is it?

What is the inverse square law, and how does it help? Basically the inverse square law states that the intensity of light from a source falls off with the square of the distance from the light source. So if the intensity of light is X at 1m from a light source, at 2m it will be X/4 and at 3m it will be X/9 and at 4m X/16. This has some interesting implications for the photographer. Firstly it means that every doubling of distance from the light source delivers a 2-stop fall in light. So, for an example, if you had a subject lit by flash at 0.5m then at a background set at 4m there would be a reduction of 6 stops of light, and at a background set at 8m an 8-stop reduction. A small increase of flash to subject distance from 0.5m to 1.0m doubles the necessary flash to background distance to get the same reduction in light (namely 8 and 16m respectively – better order your new kitchen extension now!!).

How is it Used?

Secondly, and perhaps rather confusingly, the proportional light fall off with distance is greater close-in than it is far out. This is because the light intensity is the reciprocal of the distance squared so that, for larger distances, the difference between the fractions is necessarily less than for shorter distances. So light intensity at 2m is a quarter that at 1m, ie a 3/4 (0.75) reduction between 1m and 2m. At 4m the light intensity is 1/16 reducing to 1/25 at 5m. So the difference in intensity between 4m and 5m is 9/400 (0.0225). This is useful where subjects are at different distances from the flash. Moving the flash back to say 5m from the subjects would mean that there was virtually no difference in illumination between subjects at 4m or 5m (for instance in a wedding group shot).

Other Confounders

Managing light spill can be harder where you have, for instance, a white tiled floor, or a low white ceiling. The floor can be covered in extremis (beware the trip hazard though) but there is very little you can do to mitigate a low white ceiling.

Production Images and Results

Here is the setup for this shoot. You get some sense of the restricted space and can see the camera, subject and strobe positions clearly.

Turn White Background Black

Kitchen Studio..

Post Processing

The three wine bottles shown below were all straight off the camera card and, apart from a small crop, completely unedited! So I’d have to say that the morning spent trying to turn a white background black was a complete success. I’m bound to also say, though, that I’ve no intentions of abandoning my beloved black velvet Lastolite panel background anytime soon.

Equipment Used

Equipment used was a Lastolite large panel Black/White reversible background, a Lastolite black velvet background to control spill (out of shot), 3 x Nikon SB900 Speedlights, 3 x Bowens Light Stands, assorted cold shoe clamps to attach the Speedlights to the light stands and a Gary Fong Collapsible Snoot with Power Grid for the key light. For convenience I was using 3 x Pocket Wizard Flex-tt5 radio triggers, with the mini-tt1 and AC3 controller on the camera. As you can see there is much white and silver in this room to bounce spill light around. The main kitchen lighting is daylight balanced and camera left sits a large kitchen window and patio door.

Camera and Flash Settings

The eventual camera settings were ISO 200, f11, 1/125s. The key light was set to full power and the rim lights adjusted to give a pleasing result at a much lower power (around 1/32).

Turn White Background Black

Key Light with Grid Fitted..

Use of the kitchen studio was only possible in the absence of other family members, so thanks also to them for leaving me with the house for the morning too. I think that it must be so lovely to have a permanent and dedicated studio where you are not hunting round the house for your equipment because it is all in one place. Or having to move chairs and furniture to create sufficient space. Perhaps when I retire.. You can only dream I suppose..

I feel a large man-shed coming on..

 

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Final Thoughts

Small Kitchen Woes..

To pull this off in my kitchen studio I had to use all available space and had to keep the subject size down as I was rammed against the range cooker. You can’t see it in the production shot, but I had to manage some light spill with a large black panel reflector out at camera right. For me this was a technical exercise, just to see if I could do it. I have tried without success previously as I could not manage the light spill effectively enough. The subject to background distance, for me, was only about 3m so control of light spill was essential as I couldn’t afford to only rely on the inverse square reduction.

Controlling the Spill..

If I had needed more control of light spill, I would have thought about reducing the light from the white floor tiles and used flags on the rim light flashes to stop light getting onto the ceiling. Finally it might have been necessary to use another black panel reflector on the wall behind the camera to further reduce spill.

Could do Better..

As a technical exercise, I have added to my own difficulties by using my Fujifilm XT-20 travel camera instead of my Nikon kit. I don’t have a full flash setup dedicated to this camera system so I was working with manually. I was, however, very pleased to find that my flex-tt5s and SB900s could be used on my Fujifilm XT-20, controlled by the flex-mini tt1 and AC3 controller combo on camera in the usual way. The only concession was that I had to drop the shutter speed on my XT-20 to 1/125s in order to get reliable syncing. The XT-20 maximum sync speed is 1/180s which I am confident would have worked ok with optical syncing, but didn’t with the radio kit. Since my Flex kit is for the Nikon, I’m pleased that I was able to use it on the Fuji at all, so this was a small sacrifice to make.

Cheers,

R.

Shooting Macro

Shooting Macro

I love shooting macro, though inspiration can be a little tough to find at times. I already have a 105 mm Micro Nikkor, but had been thinking about a longer focal length for some time. After some research, it seemed to me that, rather than buying the 200mm f4 Micro Nikkor which has a 20 year old design, I’d be better off going with the Sigma 180 mm F2.8 APO Macro ED DG OS. My thinking was thus. Firstly it is a faster lens, very sharp and has a good reputation. The 200 mm Nikkor, is also stunningly sharp, and built like a tank, but it is very much a one trick pony. The autofocus is very slow (though satisfactory for things a long way off apparently) and it has a maximum aperture of f4.

Making a Purchase, Checking It Out..

So, at the last but one photography show in Birmingham, I visited the Sigma stand and spoke to a representative. After looking at the lens, and hearing about it’s performance, a purchase was made from London Camera Exchange. It duly arrived, at our local store, about a week later. Had it not been a bank-holiday weekend it would have been even sooner. It’s been superb! Out of the box, the Sigma appeared well made and robust. I fitted a Wimberley Arca Swiss lens plate and set about shooting tethered using Helicon Focus. This revealed an unexpected, yet key, difference with the 105 mm Nikkor.

Bearing in mind that I had always considered the 105mm Nikkor to be an excellent lens, I was not prepared for the stunning absence of chromatic aberration. It’s not that the Nikkor is particularly bad, it’s just that the Sigma has no chromatic aberration. None at all. At least, I haven’t come across it yet. There must be some somewhere mustn’t there? But the visible difference was remarkable. With the same subject you could see the artifacting on the Nikkor but not on the Sigma. Amazing!

Choosing Between Macro Lenses

Shooting Macro

Back Garden Birds, Hide, Backlit

Choosing a lens for shooting macro requires a little thought. Firstly, what do you tend to shoot? If it’s wildlife, there is something to be said for a longer focal length to keep you more distant from your subject. This is not the only relevant factor however. Most of my outdoor shooting uses available light, sometimes with a reflector or torch to provide fill or dimension. The physical length of the macro lens I use makes little difference in this scenario, but if I’m to use flash then I need to consider two other issues.

Flash and Macro Lens Choice

Clearly, for macro shooting with flash, the length of the lens itself makes a big difference to the type of flash you might use on camera. Will the flash be a Speedlight on a flash bracket? If so, a 105mm or 150mm lens will be more useful as you can get the flash nearer to the subject. The flash bracket can reach over the lens (as opposed to be in the lens’ shadow). Here I’m using a Custom Brackets CB Folding-T folding flash rotating bracket to hold an SB900, with a Neewer SB1520 small softbox attached, to light a subject from above and to the side.

Were I to attempt this with the Sigma 180 mm F2.8 APO Macro ED DG OS I’d be out of luck. On a D500, with the APSC lens hood extension, it is approximately 330 mm in length compared to the 190 mm of the Nikkor (or aprox 115 mm without the lens hood).

Shooting Macro

R1C1 macro flash kit on a Nikkor 105mm f2.8

Using a Nikon Speedlight Commander R1C1 Macro Flash

If you are going to use the Nikon Speedlight Commander R1C1 Macro flash, for instance, you also need to bear in mind that there is no adaptor ring available in the 86 mm filter size of the Sigma 180 mm. You have to use the SB200s off lens in this case. Personally, I felt this was an inconvenience rather than a deal breaker, because when I work with flash it is usually in the studio and I can easily use stands for the flash.

Multi-Purposing a Macro Lens

It occurred to me that I have used my 105 mm Nikkor as a portrait lens in the past, ideal on a full frame camera. Would a longer prime be useful for some of my larger birds in flight work, for instance Osprey at Rothiemurchus? With a working focal length of 27o mm on a crop sensor camera (my D500), it might be a useful alternative to using my D810 with my 300 mm f2.8 (which is a much larger lens). This could be ideal for the lower light situations pre-dawn when the D810’s ISO performance is less suitable.

Lower-weight, and shorter minimum focal distance, make it a good choice for ad-hoc wildlife appearances closer to the hide.

Depth of Field Calculations

Sigma do not supply depth of field tables for shooting macro with their lenses, so ascertaining depth of field for close up work is not straightforward.

Macro Shooting

Doing the Math..

Some research was required to find out how to do the DOF maths, but with an Excel Spreadsheet I was able to produce a depth of field table. This has helped me appreciate how some of my shots might work – pre shutter release.

I guess, ultimately, if you take enough shots, you learn from experience, but knowing whether to make a virtue out of a wide aperture shot’s limited depth of field can be a little thought provoking if not enough image is sharp. I never mind taking many different shots whilst I’m out in the field, on the basis that one of them might be spot on. When I can get them onto the computer, It’s easy to see how I did, but I’d really rather know how to take the image work with a single click.

Lateral vs Longitudinal Chromatic Aberration (CA)

Types of Chromatic Aberration

Chromatic aberration occurs because shorter wavelengths of light (blue) are refracted (bent) more than longer (green and red) wavelengths of light which are refracted less. There are two types of chromatic aberration. Lateral (or transverse) and Longitudinal (or Axial).

Lateral CA occurs when all the colours are focussed at the same plane, just not aligned. R, G and B light are focussed sharply, but side by side. In Longitudinal CA, the colours are not focussed at the same plane, they are superimposed with blue in front of green in front of red. To observe this, Lateral CA causes coloured fringes around objects of high contrast, whereas Longitudinal CA causes patches of colour (ie. the most in-focus colour predominates).

The 180 mm Sigma Macro lens is particularly good with Longitudinal CA, you do not see colours change as you move up to, and then through, the focal point for high contrast details. Longitudinal chromatic aberration is very noticeable in the Nikkor 105 mm in comparison.

Recent Images

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New Year, New Profile Photo for LinkedIn

The Making of a New Profile Photo for LinkedIn

The Reason Why…

I have been working on my social media profile for a few weeks now. I have a Google+ account, with a page for TDI, an Instagram account and most recently a LinkedIn account and now Twitter. I am in the process of getting to know the strengths and weaknesses of these, how they work, and how best to engage with them and will be linking. My LinkedIn account is really to support my other career as a psychiatrist but I have previously used the same (branding) image as for TDI and my other accounts. Thinking that I probably need something a little more formal, my wife agreed to help me take a fresh portrait for LinkedIn.

A New Fridge-Freezer, A New Problem

Towards the end of last year our built in Fridge-Freezer decided that it would start freezing everything in the fridge, as well as the freezer, and to make so much ice that the drawers in the freezer wouldn’t open at all. Fearing a fire, and not having enough time to source a reasonably priced built in unit, or re-fit it in the appropriate cupboard, we elected to have a free-standing unit instead. In fairness this has been a great success, my daughter has decorated it with magnets, and uses it as a noticeboard for maths puzzles for her poor old dad to write down and solve. But here’s the rub. I can’t easily move the kitchen table out to the side like I used to, because a third of that space is now Fridge-Freezer!! So using the kitchen as a studio to capture a new profile photo is a world more grief than it used to be. Still, I needed some exercise because the weather had trashed our planned cycle ride today (too much ice this morning, too much rain and gale force winds this afternoon). Plus my bike’s not well at the moment either. So moving a heavy table and running up and down stairs a lot seemed just the ticket.

New Profile Photo

The Area to Clear, Ho Hum..

So here’s the thing, that kitchen table had to go out in the hallway. Would it go out through the doors? Could we lift it? If it was out in the hallway, could we get back in the kitchen? Was I going to be able to carry my equipment from upstairs past the obstruction? Who knew, we had to give it a try. After, that is, Helen had cleaned the floor!!

New Profile Photo

Phew, That Looks Better!!

After much shoving and scraping, and even more hoovering and washing, a space was made available in the now pristine cooking and dining area. So, whilst Helen moved on to pastures new, for further housework opportunities, I set about bringing the necessary equipment downstairs, and stockpiling it into the hallway. Hmm.. That’s a bit of a mess you’ve got there thought I. I wonder how long Helen is going to stay patient with you?

Hallway Carnage...

Hallway Carnage…

So onto the setup and test shots. I went with the D4 with 70-200 f2.8. This was going to be quite heavy for Helen, but she was confident that she could manage anything I threw at her. I decided not to shoot tethered. It was just one portrait and the image on the back of the D4, particularly with the 3 channel histogram, was more than sufficient to judge framing and exposure. I used my favorite portrait set-up of the Lastolite Triflector and Nikon Speedlight fired through a Joe McNally Ezybox with soft white interior and 2 layers of diffusion. For separation I used a second speedlight (an old SB800, in SU4 mode at 1/32 power) fired through a Bowens grid-spot attached via the rather superb Interfit Strobies XS Int326 gizmo. As usual, the camera was connected to the key light using a PocketWizard Flex Mini TT1 and Flex TT5 set up with the AC3 Zone Controller set to -2/3 exposure compensation, with ISO 200, 1/160th second and f8. Finally, my favoured Lastolite black velvet panel, suspended from a suitable stand, completed the picture.

So That's how it's Done!!

So That’s how it’s Done!!

We have daylight balanced LED lighting in our kitchen, so I left those on during the shoot. The only slight problem was teaching Helen to use the back-focus button (I have all my cameras set up this way for my wildlife photography) instead of half pressing the shutter release, but she picked this up really quickly, and didn’t need reminding to focus on the forward eye.

Until next time,

R.

NetMagic

The NetMagic Shoot

Bill and Wendy from NetMagic are friends of mine. Bill has been helping me get started with cycling again, after a 20 year rest from regular exercise (I kid you not!!). In a way, that’s a whole blog piece for another time. I’m certainly not willing to share any images of me as a MAMIL until I’m quite a lot fitter, the shame would be much too alarming for my family (and me of course!).

The NetMagic team are working on their web presence at the moment, and Bill mentioned to me that they were looking out for suitable images. I offered to help out with the corporate portraits and an image that gave a sense of the purpose of the enterprise, which is essentially all about helping students (see below).

NetMagic Tuition and Training Services provides:

  • Private tuition (GCSE and AS/A2 level) in a range of subjects
  • Exam Preparation and Study Skills support
  • University Application Advice (Personal Statement Review)
  • Oxford and Cambridge Application support with preparing to apply, the application process and mock interviews.
  • Specialist support for students with specific learning difficulties of all ages, such as those with dyslexia, dyspraxia and autistic spectrum disorder.

The Technical Stuff

I used 2 setups for the shoot. First-up was a black (velvet) background with two flash. The first as a keylight at 45 degrees above the subject, shot through my favorite double diffused, 54cm Lastolite  Professional, Joe McNally EzyBox Hotshoe. The second strobe was a hair-light shot through a grid. Both flashes were on Pocket Wizard Flex TT-5 radio triggers, and so easily controllable from camera. Both lights were set camera-left. The set (on the kitchen table, as it happens) was built with books from my study and props from the kitchen. I have heard it stated that you should use the same quality of light on the hair as with the keylight, but I really like the sharpness of a grid spot on the hair and I think that a lot of photograhers shoot that way.

The second setup was a more traditional corporate portrait affair. Keylight courtesy of Joe McNally, a Lastolite Tri-Grip reflector and a low-tech grey background (a £7 grey bed sheet, courtesy of ASDA), in this case, simply thrown over the velvet background panel and clipped on with A-Clamps to keep it taut. A hair-light shot through a grid, and finally a background light shot through a Lastolite Micro-Apollo softbox. Again all the strobes were on Flex TT-5 radio triggers controlled from the camera.

Post-Processing

Given the nature of the lighting, not too much was required. A quick run through OnOne software’s Perfect Portrait 2, the addition of mid-tone contrast from Color Efex Pro 4 and my usual 3-pass sharpening regimen.

The Images

The best way to see them is to swing by NetMagic and check out their excellent facilities. You may well know someone that could benefit from their services and they would be delighted to take your call.

Cheers,

Robin.

Photographing Roses against a white Background

Photographing Roses

A Rose by Any Other Name

I hadn’t started out to do a studio flash session photographing roses, but on thinking about what background colour would suit a white and pink rose, I realized that it had to be bright white and not grey, so the available window light session that I had planned quickly turned into something else entirely.

Photographing Roses Against a White Background

Img1141-EditPhotographing roses against a white background requires the same technique as for photographing a portrait, or anything else, against a white background. The background has to blown-out, but only just blown out, in order to avoid too much flare and contrast reduction from the resultant backlight. People sometimes talk about getting the background about 2-stops hotter than the foreground, which is another way to go, but I treat the background (which, by the way, needn’t itself be white!) like I would treat a snow scene. I will take a couple of shots with just the background lit, and increase the exposure, from metered, up a couple of stops or so, until it is just blown out. I will then turn the back-lights off and use the main light to get an exposure for the subject. For this shoot, I used 3 x SB900 strobes. 2 for the background, either side at 45 degrees, and one in a Lastolite Joe McNally Ezybox Hotshoe for the main light. I prefer to shoot manual as much as possible these days, so the Camera was set to 1/200 second at f11, ISO 200. The lens was a 105 mm Micro Nikkor on a D3, and I used 2 layers of diffusion in the softbox. All 3 flashes were set on manual, and the amount adjusted for correct exposure. I like this setup because nothing changes (except perhaps the ambient light), so all your shots are perfectly exposed and provided your strobes aren’t maxed out (1/1) you can take a small burst of shots if you need to, for instance with a moving subject.

Focus Stacking

Photographing Roses with a Manfrotto 454Photographing roses with a macro lens, close up, can lead you into problems with depth of field. This is often livable with, particularly if your shot includes quite a bit of stem and you are further back, but close-in you will have to make a decision about where to focus. I had just been reminded of the possibility of using focus-stacking in an article in Am Phog (Saturday 6th April 2013, Martin Evening’s Retouchers’ Guide), so thought I would give it a go here. By the way, Martin Evening’s books, ‘Adobe Photoshop for Photographers’, ‘The Ultimate Workshop’ and ‘Photoshop Lightroom’ are all very useful tomes if you get a chance to read them.

Focus stacking is often used in macro photography, especially for extreme close-ups of things like small insects. It is often not straightforward, however, and there are several gotcha’s to be aware of. It is best to use an uncluttered plain background because as the lens elements move, the relationship of the subject to the background can change, making the blend between layers harder to do manually (or trick the software and end up with a small areas of blur that really stand out). Having a lens that focusses internally helps (but doesn’t avoid the problem completely), and sometimes you get a better result by using something like a Manfrotto 454 Micro Positioning Plate. What this does is allows you to slide the camera and lens combination backwards and forwards by very small amounts using a thumb-screw. This can be much easier for small focus adjustments when you are very close in and the depth-of-field is only a millimeter or so, where the lens’s own focus ring gives too course an adjustment.

Photographing Roses Focus StackingPhotographing Roses, Align Layers DialogFor good focus stacking it is said to be best to use an aperture that represents the sharpest focus of the lens, which on my 105 is f8 or f11), in order to avoid diffraction effects. There are several good focus stacking software programs available, but I use Photoshop because I don’t do this very often and a bespoke software solution has not seemed warranted. The process is quite straightforward. Take a series of photographs (in this case of your roses) starting at the foremost focus point, working through to the rearmost focus point. Select the files in Bridge or Lightroom, then using the tools menu choose Photoshop –> Load Files into Photoshop Layers, or in Lightroom, right-click on the selected files and go to Edit In –> Open in Layers in Photoshop… Once the files are in a single Photoshop document. Select the layers and go to the Edit menu and choose ‘Auto Align Layers…’ using the Auto Projection method.

Photographing Roses, Blend Layers DialogThe next step is to merge the layered images together. Go to the Edit menu and select ‘Auto-Blend layers’ making sure that the Stack Images button is set and the Seamless Tones and Colours also checked. From then on it’s just a matter of clicking Ok and waiting a while. As I have mentioned, you may not get perfect results and, for this reason, you may want to manually select appropriate images, stack them, and blend them manually yourself. This is not for the feint-hearted, but does give you a great-deal of control over the final result and this is what I did here. I suspect, but have not checked out myself, that it makes a difference to Photoshop that the images are in depth-of-focus stacking order, rather than in a random order. Sometimes you get a really excellent result, other times less so. At the point of capture it is not always clear which bits of an image are at which depth, so you can end up going backwards and forwards a bit.

Until next time,

R.