Monday, 13 June 2016

TRY TIME EXPOSURES FOR ETHEREAL EFFECTS


When we think about taking long exposures with a camera, night time images usually come to mind. Only dark conditions generally call for slow shutter speeds, right?

True-but there is a way to take time exposures in broad daylight...with surprising results.

So the first question that comes to mind is: how do you take a long exposure in bright light? Won’t the camera try to set a fast shutter speed to ensure that the exposure is correct, regardless of how small the aperture is set?

Then there’s the other question: why would you want to take long exposures in daytime, anyway?

OK - a long time exposure (keeping the camera’s shutter open for a long time – from seconds to minutes) will occur when:

  • Light level is very low
  • A very small aperture is chosen, and
  • ISO is set to the lowest value that the camera will allow.

So, to answer the first question, you need to simulate low light conditions by giving your camera dark sunglasses. The device that will do this is an inexpensive thread-on piece of glass called a neutral density (ND) filter. These filters come in a wide variety of grades and are either specified in ‘stops’ or ‘times’.  They are also available as variable grade versions, often referred to as Fader NDs. Be sure to buy one that has the same filter thread diameter as your lens.

A one-stop (or two times) ND filter, with aperture and ISO remaining the same, will require that you force the shutter to stay open twice as long to get the same exposure as you would without the filter. Similarly, a two-stop filter will require slowing the shutter by four times, since a stop means a factor of two in exposure. For the kind of images I’m proposing we take, you will need a ten-stop filter in order to get exposures that are minutes long. This is equivalent to increasing exposure by a factor of 1024 times, but is usually referred to as a 1000 times filter.


Why minutes? Well, in answer to the second question above, anything moving (water, clouds) will take on a foggy (in the case of waves) or streaky (in the case of clouds) look. As long as you have stationary elements in the scene, such as rocks, ground and a tree trunk in the sample shots shown in this post, the viewer is confronted with a paradox that doesn’t appear ‘natural’. This makes for a more interesting image than if you had captured the same scene with a shutter speed of, say, 1/250th of a second. While these images were shot in colour, I converted them to black and white, since they tend to look more dramatic that way.

And now for the practical considerations. You will need:

  • A stable tripod
  • A remote shutter release that plugs into your camera, since you can’t hold down the shutter button on your camera for minutes without jarring it. You can also get an intervalometer, which allows you to set a specific time interval without having to manually time the shutter.
  • A camera with a Manual mode that will allow you to set the shutter to ‘Bulb’, or one that has a dedicated Bulb mode.
  • A day with calm winds, so that your tripod doesn’t get buffeted during the exposure.

Look for a scene that has a combination of moving and stationary components. Getting the right exposure is definitely going to take some experimentation. As a starting point, set your camera’s ISO to the lowest value it provides. This is typically 100. Do NOT use Auto ISO. In Manual / Bulb mode, set the aperture to a value anywhere in the range of f/16 to f/22. This will depend on whether it’s an overcast or sunny day. You should get exposures in the range of 2 to 4 minutes. Use the histogram to confirm good exposure and tweak the time (or aperture) as needed to get perfect exposure or desired motion effect.

With digital SLRs, a practical consideration is the heating of the sensor during long exposures. While it won’t damage the camera, this heating tends to amplify what are often referred to as ‘stuck pixels’. Every camera has them, and they appear as unexpected bright spots on the final image.

To combat this, DSLRs generally have a long exposure noise reduction setting which can mitigate this annoyance. Unfortunately, it requires that the camera will make you wait twice as long to see your image, since it takes as long again as the exposure time to process out the stuck pixels. This could result in an 8 minute wait until you take the next shot. While this technique is effective, I prefer to take my chances and fix the spots after in either Lightroom or Photoshop.

By way of a summary, here are the steps I take:

  1. Set up the camera on the tripod and compose the scene with the chosen lens.
  2. Ensure ISO is at its lowest setting, and choose a small aperture to help force a long exposure and to give me the depth of field I want.
  3. Plug in the remote shutter release or intervalometer (and set it to the exposure time I want).
  4. Thread on the ten-stop ND filter, being careful not to disturb focal length or focus settings.
  5. Cover up the eyepiece if the sun is behind me, to prevent light leak onto the image (it has happened to me!)
  6. Check my image and histogram, rinse and repeat until I get the right exposure and effect.

It’s a slow process that requires patience. At the end of it though, you will get images that will be set apart from the ordinary.

Thursday, 18 February 2016

Get Amazing Depth of Field with Focus Stacking


When we think about creating a photograph with everything in sharp focus from a few centimetres in front of the lens out to the horizon, we immediately think that we will need to ‘stop down’ to an incredibly small aperture and focus at the hyperfocal distance. Unfortunately, that means we will have to use extremely long time exposures to make up for the light lost with the small aperture, and who knows where the hyperfocal distance is anyway!?

You could invest heavily in a tilt/shift lens instead, but there is a way to use your current lenses to get this result. I am going to describe the procedure on the assumption that Photoshop is available to you, but there are inexpensive software packages available as well to perform what is referred to as focus stacking (Google it).

Before we get to the software, let’s outline the image capture procedure. The idea is to capture a number of images of the same scene (a tripod is a must for this), successively refocusing from closeup to infinity in small steps. The successive images must overlap in terms of focus. For this reason, it would be wise to use a fairly small aperture (like f/16, if the light allows), in aperture priority or manual mode, to give each shot as wide a depth of field as possible. Small focus steps will ensure the in-focus zones from one shot to the next overlap each other. This will require some experimentation with your lens. Take as many shots as you want. This will guarantee a good result, and the software will have no problem handling them.

Note that as you refocus, the size of the image changes slightly. For that reason, the first job of the software is to align all of the shots based on their content. Because each shot contains zones that are out of focus, the next job of the software is to blend the images together while removing the defocused zones from each.

When aligning the shots, the software creates a layered file comprised of each shot on a different layer (hence the ‘stacking’ term). To eliminate the defocused zones, it adds a mask to each layer which blocks out these zones individually.

So here are the steps I use in Photoshop. It is possible to align and blend all shots at once, but I found it gave me screwy results. Instead, I do the following:

1.       Open all of the shots in your sequence (at the same time to save time)

2.       Select File > Automate > Photomerge.

3.       Under Layout in the dialog box, select Collage. Under Source Files click Add Open Files. Uncheck the Blend Images Together box (I do this to avoid the aforementioned screwy results). The software creates a new, layered ‘Panorama’ file with content on all layers now aligned. Note that you will probably have to crop the edges where overlap did not occur.

4.       Highlight all layers using Shift-Click or Ctrl-Click. Select Edit > Auto-Blend Layers…, then check the Stack Images radio button and OK.

Now here’s where it can get a little tricky. If you zoom in to the resultant image and find some soft-focused areas, it means Photoshop didn’t quite get the masks right in that area. If you find a number of these areas, the fix will take time and patience. You can turn layers on and off by clicking the eyeball icon on each layer. With all layers turned off except one, you will clearly see where the mask on that visible layer has eliminated part of that layer (checkerboarded areas). By stepping this way through all layers, you will see where the trouble spots are. You may need to erase these areas from one mask (where Photoshop has left in a defocused area) and add to the mask on another layer where that area is in focus.

How do you subtract from or add to a mask? Click on that mask (the rightmost rectangle on a layer), select the Brush tool from the tool palette and choose the white patch from the bottom of the palette, and paint the image. You will see this reveals more of the image on that layer; in other words, it is removing part of the mask. To cover up part of the image on a layer (in this case, a defocused area for instance), use a black brush. Adjust the size and hardness of the brush to get the desired control. As I said, this can involve a lot of work.

First Image in Sequence
The sample images here show the first and last images in a stack sequence, and the resultant focus-stacked image. The actual number of images in the stack was 11, but the first and last images demonstrate how the background and foreground, respectively, are distinctly out of focus.  All shots were made at f/6.3, so each has a shallow depth of field. Despite that, the resultant image looks terrific.

Last Image in Sequence
Of course, if you have decent light you could avoid using focus stacking by using a very small aperture such as f/22 and focusing at hyperfocal distance. But this too requires skill in determining the right focus point.

Focus stacking may be too over-the-top for many, but if you are passionate about pushing your photography up a notch, your efforts will be greatly rewarded by trying it.


Focus-Stacked Final Image

Monday, 12 October 2015

Sharpness and Contrast: Lenses Compared


There is a vast range of pricing in lenses, so I decided to find out for myself if the most expensive lenses are really any better.

High up in this rank is the name Zeiss, and yes, the prices are out of reach for most of us. So, rather than take a chance on potential high-priced disappointment through a purchase, I decided to rent a Zeiss ZE 85mm f/1.4 Planar T for the weekend.

NOTE: Not all Zeiss lenses are more expensive than the camera manufacturers' own lenses. In fact, the Zeiss Planar lens tested here is actually cheaper by far than Canon's 85mm f/1.2 L series. The Zeiss OTUS 85mm f/1.4 lens,  however, is more than twice the price of the Canon.

My plan was to test it on my Canon 6D against the Canon 24-105mm L series zoom set to about 85mm focal length and a Mamiya M645 55mm f/2.8 medium format lens through an adaptor. Right off the bat, I must point out that it is a bit unfair to compare the 24-105 zoom against prime lenses, but after all, it is an L series lens that Canon touts as very high quality.

Also, since the Mamiya has a larger image circle than the other lenses, which were designed for a full frame sensor, only the centre portion of the Mamiya’s projected image was being used. As we know, aberrations are more pronounced at the edges, so the Mamiya has the advantage of having only its sharpest central area used in the comparison.

The test was not a rigorous scientific one. I used a test chart downloaded from the Internet for my basic comparison of resolution and contrast, then took a few outdoor shots for a more subjective head-to-head. I tried to frame up the shots the same in each case, since I was using different focal lengths (85mm and 55mm). That way, the necessity of unfairly having to enlarge the 55mm shots (and enlarging the apparent pixel size) would create a disadvantage for the Mamiya lens. Similarly, I tried matching the exposures in the camera as much as possible, but inevitably, a bit of exposure tweaking in post was needed to align the white end of the histograms. I felt this was necessary to get a fair comparison of contrast.

Test Chart Results Compared
I must preface this comparison by saying that focus is critical for a fair comparison, and I can’t guarantee that in each case I was perfectly focused. I did, however, choose the shots out of many iterations that I think represented the best focus for each lens.

The images compared here were all cropped from 100% views in Photoshop. At 100% , you are very close to seeing the limitation of the sensor in resolving detail, so even a premium lens may not seem razor sharp at such magnification.

Having said that, and with focus differences aside, the comparison is fair. Looking at the chart centre comparisons below, the Zeiss and the Mamiya seem to be comparable on a sharpness basis, while the Canon is slightly softer. This is most apparent in the fine rings in the ‘bullseye’, and in the vertical tapered stripes (next to the 16, 18, 20 marks on the right) where the Canon looks a little mushy. In fact, the Mamiya seems to have the best contrast in that zone, but critical focusing may have given it a slight advantage over the Zeiss.


Zeiss - test chart centre
 
Mamiya -test chart centre
Canon - test chart centre
Strangely, the Canon seems to give the best contrast with blacker blacks, which I would have expected the Zeiss to excel at. This, however, may be due to the fact that the Canon was not resolving the faint dot pattern (from printing the chart) that made up the black areas, and was blocking them in as solid black. Keep in mind also that the exposure was tweaked on each to ensure the white area in the centre of the ‘bullseye’ was matched across all three in terms of intensity to allow a comparison of blacks, and thus contrast.

The corner comparisons are where the differences became apparent. While both the Zeiss and the Mamiya (ignoring the chart tilt) maintained nice right angled corners, the Canon showed flawed geometry. In addition, the Canon also went very soft. Again, perhaps it’s unfair to compare a zoom's performance versus a prime's, but it’s convincing enough to make you think twice about using a zoom in a critical shoot. Also, we don’t know how the Mamiya would stack up against the Zeiss in the corners, because we’re really only using the centre portion of the Mamiya’s image circle. While very subtle, I would say the Zeiss was slightly sharper than the Mamiya in this area.

Zeiss - test chart corner
Mamiya - test chart corner
Canon - test chart corner
Subjective Outdoor Results Compared
Ok – this is where it gets even less scientific, but after all, the subjective result is probably what will convince you whether or not a particular lens will work for your type of photography.

For this comparison I used a population of one (scene, that is). Not totally representative of what a lens can capture, of course, but time eludes me on this little project.

A tripod was used to centre on the same flower bud, but slight tweaks on tripod height and position, to frame all three shots equally to compensate for focal length differences, resulted in slight differences in perspective. In Photoshop I also tried to equalize white balance and exposure.

 
 
 
To me, the Zeiss is the winner in this scenario. While the Mamiya appears to be comparable in sharpness (using the little hairs on the leaves as a reference), the contrast overall is stronger on the Zeiss. While the Canon’s contrast seems comparable to the Zeiss’, its sharpness didn’t stack up to either the Mamiya's or the Zeiss'.
Conclusions: Are the elite lenses  worth the coin?
From the moment that you first look through the Zeiss and examine the first shot, the reaction is “Wow – this is a nice lens”. After all, the heft of the all-metal barrel and the size of the glass definitely give you the impression of quality.

Before succumbing to the desire to just buy it no matter the cost, soberly think about your budget and the type of shooting you do. If you do high end portraiture or regularly sell landscapes through galleries, you can probably afford to cut to the chase and buy the best. On the other hand, if photography is a part-time money-maker, or even just your obsession, the budget-conscious do have more affordable alternatives.

I should make one other point. While the maximum aperture of the Zeiss was a lovely f/1.4, every lens performs at its worst, aberration-wise, at maximum aperture. While bokeh is gorgeous at f/1.4, there was a definite soft-focus look at that aperture. Subjectively, I don’t think the lens cleaned up until about f/2.8. That’s ok, because the brighter the maximum aperture, the sooner you achieve optimum performance when you stop down.  Bokeh still looks great at f/2.8, whereas a lens that has a maximum  aperture of f/2.8 may not perform will until you stop down to f/5.6 or smaller.

For my budget, the Zeiss are tempting, but a little too rich. I would prefer to  find used medium format lenses and adapt them to the 6D, because both the test chart and subjective comparisons show that the sharpness (while perhaps not the contrast) compare favourably to the Zeiss. One caveat: medium format lenses are somewhat vintage. Be sure to confirm that there are no signs of yellowing or coating separation on the glass before making your purchase from afar on eBay or other sites.

As a final note, don't discount vintage 35mm film lenses (with appropriate adaptors). I was going to include one in this review, but felt I needed to pull in the reins. Subjectively, I can tell you the Asahi Pentax 55mm f/2 I have was as sharp as the Mamiya and Zeiss at the centre. I suspect corner performance may not be as good, though. But for the price......

Thursday, 22 January 2015

INFRARED ON THE CHEAP

We've all seen the articles stating that you can get otherworldly infrared effects by having a little irreversible surgery done to your DSLR sensor. Without a special filter that's mounted in front of the camera's CMOS sensor, infrared light would normally spoil your images. So, in order to invite infrared light in, the filter needs to be removed. Not willing to dedicate a DSLR to infrared-only, I looked for other ways to easily get on the infrared bandwagon.

As I still occasionally shoot with medium format black and white film, the obvious thing for me was to get some infrared-sensitive film and a recommended filter. This filter is a deep red filter that favours light with wavelengths of 720 nanometers or longer. If this is sounding too techie and out of your league - hang in there - I have a simple digital solution.


By taking that same filter and holding it in front of my CCD sensor-based point and shoot camera, I was astounded at how well the infrared effect came through. Now, in colour, the image does look ethereal, but predominantly red. My preference is to either switch the camera to monochrome before taking the shot, or convert to black and white after in software. After shooting the same scenes using this technique and then using the film camera with the same filter, the results are surprisingly similar.

The reason that the CCD sensor works is that it doesn't have the infrared-removing filter that's built onto CMOS sensors. So, by using a deep red filter in front of a CCD camera lens, you are filtering out much of the visible light and letting mainly infrared light hit the sensor. Using the filter in front of my CMOS-based DSLR camera, however, I verified that the infrared effect is not really achievable.

What about using smartphone cameras with this method? Unfortunately, the newer phones seem to be equipped with CMOS sensors, so they're generally not a good candidate.

You may be wondering by now what this "infrared effect" is that I've been blathering on about. Simply, if you take picture through a deep red filter onto either infrared film or a CCD sensor on a sunny day, the vegetation (leaves, grass) will appear white or pale. It gives the impression that frost or snow has settled on the trees and lawn. At the same time, the sky appears dark, giving a dramatic contrasty scene.

Have a look at the two images in this post, both shot in summer with my point and shoot camera and the deep red filter. Have a tripod handy, though. The filter gives 5-6 stops of attenuation, meaning exposures are going to be very long.

Sunday, 24 August 2014

USING SPEEDLITES FOR BETTER RESULTS


Speedlites , simply stated, are accessory flashes that attach to the hot shoe of your DSLR. By raising the light source above the camera, the speedlite produces a more pleasing effect than the harsh head-on shadow cast by the camera’s built-in popup flash.

But there’s more to speedlites than that. Most have swivel heads that allow you to “bounce” the flash off a ceiling or wall to provide a more diffuse light source. This has the effect of softening the shadows behind the subject and more evenly filling in shadow areas on the face. Because the flash head is now well separated from the camera body, you can also add light modifiers such as a collapsible softbox. As the name implies, it softens or diffuses the light, allowing you to aim the speedlite directly at the subject rather than depending on a bounce surface. Outdoors in daylight, these are often used as a “fill” light to overcome the harsh shadows cast on the face by mid-day sunlight.

Better yet, speedlites have their own internal battery supply, so they can be separated from the camera and used in the same way as studio strobes. By mounting them on light stands and firing them with inexpensive radio triggers, you can have studio lighting anywhere, without the need for AC power. Add lightweight bounce umbrellas to diffuse the light evenly, and you can have as many light sources as you like filling an area with even, soft light.

So how do you configure this portable studio? Most of the small stuff can be bought on eBay much cheaper than at local retailers, but bulky items like light stands and umbrellas, in my humble opinion, can be sourced locally for not much more than overseas online pricing. And you have the benefit of not having to wait 2-3 weeks for product.

When it comes to speedlites and radio triggers, however, I would like to make a recommendation. While I want to stress that I have no affiliation with the company, I have found products made by Yongnuo of China to be well made and very cost effective. Just be sure that when you make a purchase that the models you choose are designed for your specific DSLR model. In some cases, their triggers are also compatible with camera manufacturers’ speedlites, but why not buy a speedlite that works as well at a third of the price?

So what is a radio trigger? If you decide to use a speedlite off-camera, you will need a means of making the flash fire when you press the camera’s shutter button. The transmitter mounts on your camera’s hot shoe and sends a signal to the receiver, which you mount on the light stand. The receiver has a hot shoe built onto it, so you simply attach your speedlite to it. Some triggers, like the YN-603, are actually transceivers, so you can use them as either a transmitter (when mounted on the camera’s hot shoe), or a receiver (when the speedlite is attached to it).

Now, there are two types of speedlites that you should be aware of: manual (such as the YN-560 III) or full ETTL (such as the YN-565 EXII). ETTL stands for Evaluative Through The Lens, meaning the camera and speedlite work together through connections on the hot shoe to ensure that the light output from the speedlite gives optimal exposure.
YN-560 III in off-camera configuration

A manual speedlite, however, requires that you set the light output on the speedlite itself by either trial-and-error or by using a flash meter. Studio setups are typically all manual. The YN-560 III has a very nice feature: built in radio receivers that are compatible with the YN-603 trigger. This means that you only need a single YN-603 on the camera’s hot shoe, rather than also attaching one to each of the speedlites to act as receivers. One feature of a manual flash is that its hot shoe connection is comprised of only a single contact point. This makes it compatible with a wide range of cameras, as opposed to an ETTL speedlite that has an arrangement of multiple contacts that are specific to a camera brand. This is why you must buy an ETTL speedlite specifically for your camera.
 
 

Yongnuo also makes an ETTL radio trigger called the YN-622. Two of these transceivers will allow you to trigger a compatible off-camera ETTL speedlite like the YN-565 EXII in full ETTL mode, meaning you don’t have to manually set the speedlite output. The camera reads the light from the speedlite through its lens and sends commands to the speedlite over the YN-622 radio link to adjust its output. You can also control groups of speedlites with these so that each has a different output level, but still controlled by the camera.

YN-565 EXII operating ETTL through a YN-622
Another benefit of using the YN-622 and a compatible speedlite on the camera is that you can use that speedlite in ETTL mode while simultaneously triggering a manual flash with a second YN-622 off-camera. That way, you can quickly move from a studio setup with two lights to a roaming subject using the single ETTL speedlite on your camera (such as in a wedding reception). The YN-622 simply attaches to the camera’s hot shoe and the speedlite attaches to the YN-622’s hot shoe.


Stacked YN-603 on a YN-622
While the Yongnuo product line is great value for money, however, I get the sense that the company doesn’t have a uniform design vision. For example, the built-in trigger receiver in the YN-560 III doesn’t exist in the YN-565 EXII. Where this becomes an issue is if you want to use the 560 and 565 together in a setup (with the 565 set to manual mode) and trigger them both from a single YN-603 trigger on the camera. Also, you can’t mix and match YN-603 and YN-622’s in a setup because they’re not compatible. You can, however, stack one on top of the other on your camera’s hot shoe and have each trigger their respective receivers.
By doing a little research, you can configure a professional lighting setup for well under $500. Just be sure that you are buying product that is 100% compatible with your camera make and model

Thursday, 20 February 2014

New Digital SLR Photography Book for 2014

"Digital SLR Photography Demystified" is my new venture in the world of photography instruction.

Originally conceived as a reference for students taking my Digital Photography for Beginners course, it also serves as a standalone guide for those who prefer self-instruction. Written in the same way as my easy-to-understand teaching style, it includes ten practice exercises to reinforce the concepts presented.

The content goes beyond the "Beginners" course by covering panoramic, high dynamic range (HDR) and night photography. Also included is a comprehensive Glossary of Terms and a Quick Solution Guide.

While no one book can explain the functions of all camera makes, a generic model is used to help the reader locate a button or menu item on their own camera, using industry-standard icons where applicable.
Support independent publishing: Buy this book on Lulu.
Currently, the book is available as a 96 page paperback from Lulu.com for $14.95 CDN + shipping (slightly less in $US). In the coming weeks, it will also become available on Amazon and Barnes & Noble websites under the ISBN 978-1-312-03258-3.

Use the QR code below to review the book on Lulu.com.


Thursday, 6 February 2014

WINTER EXPOSURE


Have we had enough of cold and snow yet? Unfortunately, it doesn’t look like it’s going away any time soon.

So – if you have the itch to get out and take some photos anyway but are disappointed with the results, the problem may be with exposure. The photographic kind, that is. The camera meters (measures) the light coming through the lens and tries to ‘average’ the exposure to a mid-grey (referred to as 18% grey).

With Evaluative (Canon-speak) or Matrix (Nikon-speak) metering, the camera reads the light over several zones in the viewfinder. If a bright scene covers most of these zones, the computer in the camera will calculate the exposure based mostly on these bright zones. In winter scenes – guess what – snow tends to dominate the scene and the camera tries to expose it to a mid-grey. So, if your winter shots are a little dark, that’s the reason.

There are two fixes for this: spot/partial metering and exposure compensation. I find the latter is the easiest solution so I’ll address it first.

 
Exposure compensation is a means of overriding the camera’s metering, by allowing you to over- or underexpose by an amount chosen by you. It’s normally controlled by pressing the +/- button and turning the command wheel on the camera. As you do, a bar graph (depends on the camera) will indicate by how many stops you are changing the exposure.

Since the snow caused your camera to underexpose, you need to dial in some overexposure or + exposure compensation. I typically use about one and two-thirds stops, but you may need to use something different depending upon how much of the scene is occupied by snow. Just don’t forget to dial it back to zero when finished, because it won’t go away when the camera is turned off.
 
Partial or Spot metering relies on something that has a mid-grey tone (although it can be a colour like facial skin) centred in the viewfinder. It effectively ignores all the white snow around it and exposes based on the face or mid-grey object.

I hope this helps, because there’s nothing I can do about the weather. If you need a little more help,  check out my photography courses at www.filmscapes.ca