Tuesday, November 29, 2016

Spot Metering Exposure Control: fotofusion Workshop Notes


Spot Metering: Customized Exposure Control
fotofusion 2017 Workshop Notes

London 2015: f/8 at 1/1000 sec, ISO 250. Spot reading on tan forecourt, no exposure compensation.
Photo copyright George Schaub


How It Works: Spot metering is a refined and personal way to control exposure. It was used in ye olde film days to “nail” tonality. With black and white film it was used in combination with development procedures to create a full tonal scale negative. With color slide film it was used as a way to control highlights, to avoid “burnouts” due to overexposure and, on the other hand, saturate color. Somewhat ironically, procedures for making exposure decisions when shooting digital are similar to those when shooting slides. Highlight control is essential with digital to insure that there will be no or minimum clipping (loss of values in the brighter areas); color saturation and value can also be precisely controlled.

Unlike Matrix or Evaluative metering, which reads much of the scene to arrive at an algorithm of exposure, spot is a personal and selective metering control that reads one area of brightness and “moves” it to middle gray. Thus, if you spot read a black wall it will record as middle gray; if you spot a white wall it records as middle gray.

That may seem academic, but the true value of spot metering is that you can “move” that middle gray value by a simple procedure to insure that highlights are within range, to saturate certain colors, and to maintain low key moods or values in your initial exposure.

Here’s how it works and how to use it:

Exposure Control: You can use spot metering pattern with any exposure mode. The easiest method, and the most interesting and engaging, is Manual exposure mode. You set this by placing the exposure mode dial on M. You can, if it feels more comfortable, use aperture or shutter priority, but this automation leads to a bit more complicated procedure that entails autoexposure compensation.

In M mode and spot metering pattern the exposure system reads out the brightness in a specific area, generally the center of the frame. Your job is to first make the reading and move aperture or shutter speed values so that the indicator on your exposure readout (the hash marks on the LCD or in the finder) sits in the middle of the scale. This is your “base” reading, your middle gray. You then add or subtract exposure to “move” that value plus or minus (lighter or darker, respectively) depending on your intention for that value. You do this by changing either aperture or shutter speed; in most cameras there may be two dials, one for each. If not find the way to change these settings and use it.

Note: You will notice the scale has plus and minus points: these indicate the “exposure compensation” you will set.  

Readings: Turn your camera to spot metering pattern, usually indicated by a small dot in the middle of the metering pattern symbol. Hold the camera to your eye and press the shutter release lightly to insure that the center indicator lights up. (Note: in most cameras when you switch to spot this will automatically happen. Spot sensitivity, where light is read, is a small circle (or rectangle, actually a bit of an oval) in the center of your viewfinder, and only that area.

Note: This method means you do not need to “lock” exposure or use any exposure compensation dials.

Frame and “place” the spot over the desired area, say a highlight. Note your readings. Move the aperture or shutter speed dial so that the exposure indicator (a delta or hash mark) is at the center of the scale (this is called “nulling it out.”). Being in Manual exposure mode, this locks the reading. You no longer need take any other readings of that highlight or use exposure lock to hold the reading. In fact, you can shoot with comfort  as long as the lighting does not change.

The next step is to decide whether you want that reading to be the final exposure or if you want to compensate the reading to “move” it (the read value) up or down the brightness scale.

For example, if you read a bright area and do nothing it will record as middle gray; to retain the bright character of the area you then compensate, using the exposure dial to reach  +1 or 1.5 on the exposure scale. You do this by changing aperture or shutter speed and making sure the indicator goes into the plus range.

If you read a dark area and want to keep its character, set at minus -1 or 1.5.

In general, highlights are the key here, as a highly overexposed highlight is much more difficult to retain.  Shadow areas can be opened more successfully in post processing.

Keep in mind that exposure works in “lock step.” It is the blink of an eye. So, if you read a bright highlight or rich color and null it out (do not compensate) all the other values below that brightness will become darker. Likewise, if you read a dark area and null it out all the other values above it will become brighter.


The light control (aperture or shutter speed) you choose to make this change depends on the image effects you prioritize. For example, if you want to retain the aperture, thus depth of field, change the shutter speed; if you want to retain the shutter speed, change aperture. This will be subject and light dependent. Don’t be afraid to raise ISO, within reason, to gain more leeway if need be.

Focusing
After making your exposure settings you can use manual focus or autofocus. If you use autofocus, note that the focus will usually be obtained using the center spot area as well. You can lock on subjects using the AE/AF lock button or slight pressure on the shutter release and move around the frame if need be; for example, do this if you want to focus onto an off-center and close subject. Note: Locking has no effect on exposure because you are in Manual exposure mode; it just affects focus. Personally, I prefer manual focus, although those with only a monitor viewfinder may find this unusable in bright light.
 
Compensation: Compensation means adapting the read light to the intention of the exposure. The easiest way to consider compensation is to understand that whatever you “spot” will turn middle gray. Thus, when a bright area is read you might have to add compensation (keep a bright area bright: move it “up” from middle gray) or subtract (in overall dark or moody scenes: move it “down” from middle gray). This might seem counter-intuitive, but if you keep in mind that spot metering will turn a perceived bright area darker and a perceived dark area lighter it will become second nature.

High Contrast: The biggest challenge in photography is high contrast light, when there is a wide disparity between bright and dark areas. Yet, this is often the lighting condition that creates the most striking images. In digital, you have to control the highlights. Shadows have much more leeway in post processing. Thus, use spot in high contrast conditions to tame highlights. If your aim is silhouettes simply read the “ground” (background) and the “figure” (foreground) will go darker.

Color:  One interesting benefit of spot metering is in color rendition, especially of brighter or higher frequency colors like red, orange and yellow. Spot them with no compensation and you will find that color richness will result, simply because you are darkening the colors, thus saturating them. Of course, if there is a brighter tone, like white highlights, they have to take priority.

Mood: Not every shot has bright values. Using spot and minus exposure, you can retain the deep mood of low key scenes right in the camera.

Spot and HDR: If you like shooting HDR (a sequence of bracketed exposures that you combine later in processing or even in camera) make your first shot the spot read highlight and then bracket +1 and +2 up and - 1 stop down. This will guarantee that you have frames with saturated highlights and open shadows .

Benefits of Spot: Practically, when you want to insure the best exposure for certain scenes, especially those with high contrast, spot metering can cut down on wasted shots and deliver the best exposures of any subject or scene you’ve ever made right out of the camera. It will also make you a better and more involved photographer by teaching you a lot about exposure and light. And best of all it will positively affect the way you see with a photographic eye and expand your appreciation of the light around you.

Field Exercises

1)   Find a bright white highlight: read it with spot. Make an exposure. Then add plus 1 exposure and retake. Compare.
2)   Find a deep shadow area dominated by dark tones. Make a spot reading and exposure. Subtract 1 stop. Compare.
3)   Find a colorful red, yellow, or orange flower or wall. Spot read and expose. Note different color saturation effects.
4)   Find a high contrast scene. Read the highlight and add ½ to 1 stop. Note highlight rendition and deep shadow effect.
5)   Find a “split” scene (half bright highlight/half deep shadow). Read the scene with Matrix metering or equivalent, then use spot and compensate technique on both shadow and highlight areas.
6)   With the sun coming over your shoulder, read the sky and expose.
7)   With sun facing you, pose a subject who falls into his or her “own shadow.” Make a Matrix read exposure of a three quarter shot/then spot the subject and expose.
8)   Find a scene where there is a “sliver” of highlight. Make a Matrix reading and expose. Then expose using spot on that sliver (plant branch etc.)
9)   Find a bright white subject. Make a spot reading and expose. Then add +1/2, +1 and + 1.5 stops.
10)  Do the same with a low key scene.
11)  Work with direction of light using spot. 90 degree side lit, 45 degree side lit. Front lit. Back lit.

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Notes posted on George Schaub Blog (type in search engine) under fotofusion Spot Metering Notes

Wednesday, November 16, 2016

Canson Baryta Prestige 340gsm: Paper Test and Review


 Canson’s new Baryta Prestige is a 340 gsm inkjet paper comprised of acid-free alpha-cellulose and cotton white paper with a true Barium sulphate (“baryta”) coating. The baryta nomenclature tags it as having the look and feel of silver halide prints that will appeal to those who know what that entails: for those who don’t it is a durable paper that brings a feeling of richness and depth not only to tonal values and hues but to the surface and weight of the paper itself. Inks seem to blend in with the surface rather than sit on top, a very pleasing look.

It is a “smooth gloss” paper, which means that it has the look and sharpness of traditional glossy paper while lacking the distracting sheen of a “hard” surface gloss. For those who have worked in a darkroom that’s like double-weight glossy dried matte. It has a weight and durability that while defending the sheet from handling problems does not prevent the user from using virtually every photo inkjet printer (not all-in-ones) out today.

I tested Baryta Prestige using a Canon PRO-1000 and Epson SureColor P800, thermal and piezoelectric inkjet printers respectively. I worked with three images: one with bold color, one a mixture of monochrome and color areas, and one “straight” black and white.

Test Results
Both printers handle up to 300gsm weight papers through the normal single-sheet feed paths, but being heavier weight I loaded the paper using the Epson front-feed and Canon back/manual feed trays. While I would advise flexing the paper to help it maintain flatness with the Epson, the Canon manual tray path passed the paper through with no problem. (There was no problem with the Epson either; it just seemed to be less than flat when feeding it so I flexed it prior to aligning it with the guides and it passed through with no skewing whatsoever.) 

I processed the images in Adobe Photoshop CC 2015.5 on a MacBook Pro that is calibrated to my Cinema Display. I downloaded the Canson ICC profiles (www.canson-infinity.com/en/icc-profiles) and worked with Photoshop Managed Color/Perceptual Intent on two color images and black and white modes (printer controlled color in the Epson and the Canon black and white print checkoff in the driver). I made no adjustments to the processed image between printers.  The paper profile and surface called for PK (Photo Black) ink. If you have matte black set up in the Epson you have to wait a bit while it switches to Photo Black; the Canon uses two separate feeds for PK and PM inks so no swapping time is required.

Overall both printers delivered very good results. Colors were rich and true and highlight texture is nuanced. The paper surface has a very slight stipple (unlike a hard gloss) and there is no noticeable gloss differential. The weight of the paper is such that mounting and matting will present no problems; overall it has a substantial and durable feel.

Canson ICC profile, Photoshop CC 2015.5, Madrid Wall Composite copyright George Schaub

In the color image, the Canon delivered a cleaner (somewhat brighter) yellow and a slightly more differentiated red.  Both printers yielded a rich D-Max (deep black) with nice tonal gradation from dark to light gray. Bright whites were clean with very subtle highlight values down from bright to soft white. Blues and cyans seem richer on the Epson print. These comparatives are based on side-by-side prints: taken alone each is very good and would be more than pleasing to the eye.

Canson ICC profile, Photoshop CC 2015.5, Composite 2 copyright George Schaub

I chose a composite graphic with both grayscale and subtle color touches to check how the Canon and Epson would handle the black and white values without using the monochrome checkoff option in their drivers. The dark tonal areas of the monochrome values in the image were reproduced with a rich and even startling depth; highlights maintained their starkness without loss of textural nuance. If anything, the SureColor P800 yielded richer reds and subtler blues, a result that was apparent in the full color image print as well.


I chose a monochrome image that displays a very wide gamut of values, from creamy and textural whites through a range of grays to deep black. I used the “black and white” checkoff in the Canon driver and Epson’s Advanced Black and White mode. Both prints showed a depth and tonal separation that was very pleasing, with the Epson printing out a tad darker overall. I would not hesitate to use this paper for any of my monochrome images.

Conclusions and Recommendations
Now that we have printers that can yield excellent results, printmakers owe it to themselves to work with inkjet papers that can bring out the most vivid and vital tonal values and hues of the image itself. Working with the ICC profiles and, with monochrome images and settings in the respective printer drivers, Canson’s Baryta Prestige showed itself to be an excellent partner to these two quality inkjet printers. New to the market as of fall, 2016, it can take its place among the thoroughbred class of fine art papers that has the weight, surface, optical density, wide color gamut and archival characteristics that will allow you to make prints that you will be proud to display.

Contact, size and pricing: www.canson-infinity.com/en


  


Thursday, June 16, 2016

Canon EOS 80D Lab and Field Tests


This test was performed by Betternet, TIPA's camera testing lab. I edited the comments and results from their report and am a member of TIPA's Technical Committee.



The new Canon EOS 80D is an SLR system with an APS-C size sensor. The follower of the 70D, which was introduced in 2013, it offers higher resolution (24MP) than its forerunner (70D: 20 MP) and a lot of up-to-date features. It has an EF-S mount and is able to use all EF/EF-S lens systems.

The camera is very compact. It is nearly the same size as the Canon EOS 750/760D (Canon Rebel T6i/T6s). The design looks very similar to this entry-level camera, but the function elements of the new camera show some differences. The Canon 80D offers an 8-way control field, which is helpful for navigation in image playback mode, when using the magnifier function in live preview mode, or when setting up the desired focus sensor. By using the control field the user can activate the focus area very quickly and intuitively.



The new Canon offers a fast AF system with 45 AF areas, which are all cross type sensors. 27 of these sensors are very fast/light sensitive and allow for work with a wide range of lenses. The focus system is highly configurable: the photographer can choose single AF areas, groups of AF sensors, and more. To configure or set up the AF system the camera has the well-known “AF sensor” button on the back and a second, small focus system button directly beside the shutter release button. Choosing an AF area or configuring groups/AF areas is very easy with these buttons in combination with the setup dials and the cursor control field.

The compact body of the Canon EOS 80D is well balanced and fits comfortably in hand. Many function elements allow for quick setup of all parameters. The camera has a setup dial right behind the shutter release button and a second wheel/rotary knob that encircles the 8 way cursor field, so setting up aperture and shutter speed in M mode is very comfortable. In all, the camera supports easy menu navigation and image parameter setup. A large and illuminated status LCD displays the most important settings.

The new Canon has a large 3-inch screen on the back with high resolution (1,040,000 RGB dots). This LCD can be used as electronic viewfinder. To activate this viewfinder the camera offers an LV switch right beside the ocular of the optical viewfinder. The LCD of the 80D is touch sensitive. The touch screen can also be used for parameter setup by pressing the “Q” button and choosing parameters like ISO speed or the EV compensation. The monitor of the Canon EOS 80D is fully articulated and can be rotated to the left hand side or even to the front of the camera.



As a mid-range SLR system the camera offers a small pop-up flash system, which is very helpful in many situations. The camera supports Canon’s “E-TLL II” system and wireless multi flash systems for Canon Speedlite flashes, which can be mounted on the accessory shoe on top of the camera.

The new Canon also has a Wi-Fi module including NFC, which allows users to establish the wireless connection between the 80D and a smart device. The free app for Apple iOS and Android allows image transfer as well as using the smartphone/tablet as a remote control.






Image Quality Lab Tests
Color: The EOS 80D showed an excellent performance in our color test. The automatic white balance system did a very good job, so the gray pattern for neutral color nuances are located nearly exactly in the center of our GretagMacbeth chart. Red colors are slightly boosted by a higher and brighter yellow rate. Skin tones are reproduced perfectly. The overall saturation is also nearly perfect. The Canon 80D reproduced the test chart with 98.8 percent. Our field test shots give proof of the very good color results of our test charts.



Sharpness: The Canon EOS 80D reproduced the ISO 12233 test chart with 3634 of 4000 lines, which is a very good result. The camera showed some over- and under-shot effects on hard contrast lines: the conclusion is that its DIGIC6 processor uses an intense filtering to enhance sharpness. Fortunately, it isn't intense enough to create real clipping effects, but the boosting of sharpness may be visible in some image elements. In our real life shots, this effect isn't as intense as in the shot of test chart. The camera seems to intensify filtering effects depending on the scene. The test images were taken in default settings, so the “Picture Style” was set to “Auto”, while most other Canon SLRs use “Standard” with a fixed setup for sharpness, contrast and colors.

Noise: The EOS 80D performed in a typical way for Canon SLRs in our noise tests. At lower ISO speed settings luminance noise level is a little higher than in images taken with other APS-C cameras, but the color noise is very low. Color noise artifacts get visible in images taken with ISO 1600 and clearly visible in images taken with highest ISO speed settings of more than ISO 6400. The results of the highest ISO speed settings (12,800/16,000) are still acceptable, but in additional high mode up to ISO 25,600 it becomes more intense.

The dynamic range results are on an average or good level. The camera reproduced the Stouffer 4110 chart with a maximum of 10.9 f-stops with reduced dynamic range in images taken with higher ISO speeds.