Tag Archives: tripod

Understanding the myth of “Crop Sensor” cameras.

Why crop sensor cameras do not produce greater subject magnification than their full-frame brothers.

I am disturbed by a lot of talk over the last few years stating that cameras with “crop sensors” produce larger in-camera subject size to cameras with full frame sensors. This thinking is both incorrect and continues to mislead the photography world. I feel this misleading language comes from two camps: One, the marketing folks who try to tell us that with a 1.6 crop sensor our 200mm lens is now a 320mm lens. And two, the wildlife photographers who want large in-camera images and who use a crop sensor camera believing the crop sensor somehow produces greater subject magnification.

Let me provide a couple of examples of that talk:

“For nature, wildlife and sports enthusiasts, it might make more sense to stick with a smaller sensor. You can take advantage of the crop factor to get maximum detail at long distances.” http://digital-photography-school.com/full-frame-sensor-vs-crop-sensor-which-is-right-for-you/

 “…the Mark IV has the 1.3 crop factor and a higher megapixel count than the D3s, which are nice for telephoto work.” http://www.deepgreenphotography.com/the-gear/

 “Focal length measurements on lenses are based on the 35mm standard. If you are using a crop frame camera the sensor is cropping out the edges of the frame, which is effectively increasing the focal length. The amount of difference in the field of view or focal length with a crop sensor is measured by its “Multiplier.” And,

 “…while a crop sensor DSLR doesn’t provide the same level of image quality as a full frame DSLR, it does [offers] sic. major advantages when it comes to cost. It can also be very effective for telephoto photography for the extra reach gained from the crop sensor multiplier. For example, this can be very useful when shooting sports, wildlife, and other types of photojournalism…” both from: http://www.slrlounge.com/school/cropped-sensor-vs-full-frame-sensor-tips-in-2/

 First let me state two facts: One, images from crop sensor cameras are not inherently of lower quality than those of full-frame cameras and, two, crop sensor cameras produce exactly the same in-camera image magnification as do their larger full-frame brothers.

Before I take this discussion of why these facts are true, let’s understand some things about cameras and their sensors.

First, a full-frame sensor gets its name from the fact that is physical measurements are, in round numbers, 24 x 36 mm. That’s the same size of our old standby, the full-frame 35mm film negative or transparency.

Second, I truly believe that the term, “crop sensor” is a misleading term. It is simply a sensor that is smaller than the full frame cousin. And there are now several sizes of “crop sensors”. They range from the APS-C (15.7 x 23.6 mm), the APS-H (19 x 28.7 mm), four thirds systems (13 x 17.3 mm), and even smaller. So there is really no “Standard” when it comes to identifying a sensor size.

Now let’s talk about the lens for a moment, the image forming device that projects our picture on to the sensor. Lenses have several characteristics. They affect:

  • Image size. This is governed by the focal length. Longer focal lengths produce larger subjectdetail on the sensor at any given distance,
  • Angle of view. This is the area of coverage in front of the lens that the lens may capture and project on to the sensor. It too is governed by focal length. Shorter focal lengths produce a wider angle of view that longer focal length telephotos for example. And finally,
  • Perspective. This is a relationship of components within the image to others within the same image. Focal length affects perspective, but only when the lens-to-subject distance is changed.

Crop sensor-Example 1

Let’s look at the image above to understand the physical relationship. The large frame is that of standard 35 mm film and also that of a full frame digital sensor. The yellow outline represents the area and magnification of an APS-C sensor, similar to that of a Nikon D2X or D7100 series camera body. The image was taken with a Nikkor 80-200 mm F 2.8 zoom lens.

Lenses have physical characteristics in addition to the optical characteristics above. One that is most important here is lens flange-to-sensor distance. This is the physical distance from the rear mounting flange of the lens to the sensor. That distance is specific to allow the lens to be focused at infinity. This distance is somewhat different between manufacturers, but it is standard within a manufacturer family so that all lenses will work properly.

In order for a lens of any particular focal length to produce larger image details on the sensor, the lens must be moved farther from the sensor or closer to the subject. Since the flange-to-sensor distance must be the same for cameras of a particular brand, any given lens (of that brand) will produce an image of the same magnification at the sensor regardless of the sensor dimension. What changes is the area of the projected image, not its magnification.

So let’s look at how this works.

The set-up

A standard, single focal length 200mm prime telephoto lens is mounted on a tripod. A subject is placed at a constant, pre-measured distance from the lens for all images. And two camera bodies, Nikon D90 with its APS-C sensor and Nikon D800 with its full frame sensor, were used.

The Process

Two photos of a mounted scaled quail are made from the same spot. Nothing changes but the camera bodies. Both images are processed in Photoshop in the same manner. A new composite file was made using both images together. Each image was reproduced at the same magnification for comparison. The APS-C image is produced at a six times multiple of its actual size of 15.7 x 23.6 mm, and the full frame image is printed at the same six times multiple of its actual size of 24 x 36 mm.

The Result.

One can clearly see the subject is the same magnification on both sensors and the reproduction sizes of the bird are the same for both sensors. The full frame sensor on the left captures significant additional area than the smaller sensor. This is the source of the term “Crop Sensor”.

Crop-Full Comparison

Left: Full frame sensor, Nikon D800. Right: Nikon D90 APS-C sensor. Initial enlargement (left) = 6 times sensor length 36 mm x 6= 216 mm. Initial enlargement (right) = 6 times sensor length 23.6 mm x 6= 141.6 mm.

The Misconception

When both images are reproduced at the same dimensions, the APS-C subject is reproduced at a larger size. This is only because the image is blown up to be the same reproduction size. This is why some people think there is actual in-camera magnification increase.

When viewed in the camera through the viewfinder or in live-view the smaller sensor frame is filled with the subject at a given distance than the full frame sensor. Therefore, the APS-C camera appears to produce a larger image. This is simply because the frame is filled faster with any given focal length and subject distance. What actually happens here is that the APS-C (crop sensor) image is blown up to match the outer dimensions of the full frame image.

Same enlargement comparison

Left, Nikon D800 full frame sensor. Right, Nikon D90 APS-C sensor.

Image quality

Image quality is not entirely based upon image size at the sensor, but is based upon in-camera processing technology, pixel size and pixel density. Many “crop sensor” cameras have better sensors and processing engines than full frame cameras. But that’s another story. (Maybe later.)

Copyright © 2014 Brian K Loflin . All rights reserved.

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Sights and colors of Autum

The last week of September, I took a short trip to Rocky Mountain National Park in Colorado. In addition to getting some much-needed “away time”, I wanted to photograph Elk in the rut and the colorful Aspens at their peak. I was surprised to discover that I arrived at the best week- for both!

BullBugle-4630-Sm

 Nikon D-800, 600mm F4.0 Nikkor lens, tripod.

The bulls and their hormones were very active and good images were easily found. The color was a bit splotchy as there was a previous beetle kill in the the pines. But a little perseverance paid off with some nice color.

Aspens-5076-Sm

Nikon D-800, 80-200 mm zoom Nikkor lens, tripod.

Copyright © 2014 Brian Loflin. All rights reserved.

Small, smaller, smallest: A work in progress

Commonly, when we think of close up images we envision filling the frame with subjects the size of a butterfly. When we think of macro, that subject size becomes smaller by a factor of five or so. That might be a small beetle or maybe a fly. There is a vast world that is much smaller that is worthy of our photography prowess. That is the world of ultra macro or indeed micro photography.

There are many tools used for life-sized images. The macro lens, extension tubes, bellows attachment and even microscopes. Each has its advantages,  disadvantages and limitations. Some of the major considerations when doing image capture at magnifications vastly greater than life-size include, image resolution, focus, depth of field, lighting and vibrations to name a few. The micro world is a challenging one indeed.

DA01-bloflin0312

The above image is the head of a bee. It is magnified about 1.6 times on the sensor. This is not a very great magnification, but in order to capture sufficient depth of field in this image 53 individual images with a different point of focus from the antennae to the rear of the head were made. Each image was spaced 0.005 inch from one another from the front to the back. These multiple images spanned the overall distance of o.265 inch.

Image making like this calls for a stable specimen and camera platform, precise and uniform movements in focus and absolutely uniform, clean lighting. In order to accomplish this a bellows and true macro lens was used with a micrometer specimen stage and electronic flash. All this apparatus may create a big problem: movement through vibrations. This really reduces image resolution.

To overcome the problems, I am assembling a specialized piece of equipment to enable the precision required. This is my work in process. The idea is not new, per se, but getting all the pieces together has been interesting. It looks like this:

Micro-6098-Sm

This micro set up is designed for versatility and for use from magnifications of 1:1 or life-size on the sensor with a 55 mm macro lens to magnifications of close to 40:1 with a true microscope lens on the bellows.

Camera movement is facilitated by a geared linear positioner with provisions for a stepper motor, an Arca-style plate on the positioner table and the focusing rail of the Nikon PB-4 bellows.

Subject positioning  is possible in all three X, Y, and Z planes. A cannibalized AO microscope stand provides coarse and fine movement in the vertical direction. A linear motion micrometer stage provides movement in X and Y directions. The specimen is held by an articulating holder mounted on the linear stage. (See Variable macro specimen holder) This holder will facilitate the use of pinned insects in addition to other larger materials fastened to the stage itself.

All this assembly is mounted together on a platform to reduce independent vibrations. The weight is substantial, providing additional aid in mitigating vibrations. While the current prototype mounting base is dimensional lumber, future refinements include an all-metal positioning table and the addition of a stepper motor for automating focus stacking.

The clean design without bulky tripods and other equipment in the way allows the use of SB-800 or SB-910 electronic flash on articulated arms in a unobstructed manner.

A future post will visit images made in much greater magnifications. Improvements to image resolution will be measured and discussed. Stay tuned!

Portraits vs. Patterns

More frequently than not, most photographers discover a wonderful object and line it up in a traditional sense for a nice portrait shot. Myriad numbers of flowers are captured daily around the world. We like flowers; the colors and aromas dazzle and mesmerize us and stimulate our desire to capture the beauty.

When we set up, we think of the many things we have learned about exposure, depth-of-field and the rules of composition and nine out of ten times come up with a very nice image when it clicks. The backyard iris below is one of those images.

Nikon D2Xs, 200 mm F4.0 Micro Nikkor lens, Gitzo tripod and hand-held diffuser. (Both images.)

But if you work with your subject long enough- and you should- you will discover other marvels, often overlooked at first glance. To work your subject I will repeat the instructions of my mentor, Bob Sisson, 45-year natural science photographer at National Geographic.  “Hoover the subject,” he would say. Like using the vacuum cleaner of the same name, Bob would admonish me to, “move around the subject on all sides, get low and high and move in close for the details.” Here is where the magical image lives.

And Bob’s advice is most always correct. There is magic in the details. And it usually isn’t the first image the you visualize. Compare the image below of the same blossom. You choose.

So the story goes. Take your time and make photographs don’t just take pictures. Hoover the subject for the best images. And take at least three views: the environment (or habitat) shot, the portrait (or habit) shot and then go in for the close-up details. That’s where the real beauty may hide!

© 2012 Brian Loflin. All rights reserved.

Painted surprise

Boy Scouts have a motto that states: “Be Prepared”. This motto is a perfect one for the field photographer because one will never know what you may see if you really inspect the environment closely. This may change your photographic direction significantly.

Yesterday while on a wildflower trip to the Texas Hill Country near my Austin home, I stepped out of the vehicle prepared to make a wide angle landscape image of a display of wildflowers. However, I stopped to look at some Indian blanket flowers (Gaillardia pulchella) and spied this well-hidden moth  on one of the blossoms. Not to pass up the opportunity, I quickly switched to a macro lens and fill flash to capture the miniature surprise in front of me.

Painted schinia moth, (Schinia volupia). Nikon D2Xs, 200 mm F 4.0  Micro Nikkor, SB-800 flash, Gitzo tripod.
 

This Painted schinia moth has a wingspan of 20–22 mm and is found from Arizona to Texas, and north to Nebraska in open fields and meadows where the host and larval food plant Indian blanket (Gaillardia pulchella) thrives. It is often seen resting on the flower heads of the host plant, as above, and is attracted to lights.

Copyright © 2012 Brian Loflin. All rights reserved.

Extreme Macro Depth of Field

Again and again, we have learned that there are several occasions where a single, yet well-executed, digital image may not capture the expected results. Most commonly we see High Dynamic Range images from a series of bracketed frames
providing greater tone values of a scene than possible with a single exposure.

Many pictorial images have a very wide Depth of Field range that somewhat limits the capability to capture front-to-back sharpness in a traditional digital image regardless of the aperture selected. We have also learned this DoF is dependent primarily on Aperture, then on Subject Distance, and lens Focal Length. As we get closer to the image in macro photography, the total measured distance of the DoF gets smaller. Therefore, we need to improve upon this fault.

Like in HDR, with the Extreme Depth of Field process we rely upon the blending of several images into one with greatly extended DoF. Each image is focused at a different distance from the lens. When blended in computer software, part of the resultant image uses near focus detail, part uses mid-focus detail and another uses far focus detail, and so on. Often, as many as 10 or more sequential images are “stacked” and blended into one.

This blending process can include the use of multiple layers in Photoshop or a free software called CombineZ. However, the most powerful software and today’s industry standard is Helicon Focus. The current version is 5.2.16 and its cost ranges from $30 to $200 depending on length of subscription service and number of computers licensed.

Nikon D2Xs, 50 mm flat field EL Nikkor lens on bellows, two SB-800 flashes, tripod. Image magnification in camera: 1.6X.

In this image of the head of a bee 53 individual images with a different point of focus from the antennae to the rear of the head were made. Each image was spaced 0.005 inch from one another from the front to the back. These multiple images spanned the overall distance of o.265 inch.

The screen shot above is from Helicon Focus. It illustrates the blending of these images into the resultant single Extreme Depth of Field image of the bee. The two images below demonstrate the difference in focus from one of the more front images to one of the most rear images. As illustrated, the DoF of any of the images is nil at this magnification.

A most helpful tool for capturing the many individual images required is a focus slider, a tripod mounted, rail-like device that facilitates the movement of the camera backward and forward at very small increments, thus changing the point of focus. (Moving the camera for focus is done as opposed to rotating the lens barrel normally which would change magnification at this scale.)

In my lab, the camera remains stationary and solidly mounted on a heavy tripod. I use a micrometer stage to move the specimen which provides infinite, yet measured travel over a distance of just more than one inch in measured intervals of 0.001 inch. This process proves most ideal when dealing with insects and other tiny specimens. This equipment set-up with a variety of macro lenses is capable of producing images up to 40X magnification. (See image below.)

Camera and bellows with focusing rail mounted on heavy tripod, specimen on micrometer stage, twin SB-800 on articulating arms with ball heads, auxiliary battery power for Speedlights, electronic cable release.

As in other high-magnification applications, any movement of the camera or subject is most detrimental to image quality. Therefore, solid mounting is paramount. Bolt everything down on solid, vibration-free surfaces. The heavier, the better. In addition, use an electronic cable release and mirror lock-up to minimize motion at every possible point.

The use of electronic flash with its inherent high speed flash duration is most helpful. This is especially true as at great bellows extension, a lot of light loss is encountered. Flash provides these high light levels required for appropriate exposures. As a side benefit, the use of high shutter speed synchronization will also help reduce image deterioration due to internal camera vibrations. As a rule, I generally use 1/250 to 1/500 second shutter speeds at ISO 100 with flash. With these settings I can use the “sweet spot” aperture of F8.0 for highest resolution.

Extreme Depth of Field techniques are exceptionally useful in macro, but the technique is not limited to macro images alone. Remember, DoF is affected
by aperture, lens-to-subject distance, and lens focal length. So you are able to use EDoF whenever given aperture and selected focal length precludes deep DoF.

Copyright © 2012 Brian Loflin. All rights reserved.

Portrait vs. Story Shots

Many times we see published images of absolutely gorgeous subjects- plant, animal and mineral. When we examine the photography it is flawless. It has perfect exposure, great focus, amazing detail, appropriate depth of field and just the right light. Silently, we wish we had taken that shot. Like the roadrunner below.

Both images: Nikon D2Xs, Nikkor 600mm F 4.0 telephoto, Gitzo tripod.

But then we think what is the subject doing? Posing for the camera! How clever. Must have been a set-up shot. And many are. That’s not all bad by any stretch of the imagination. Photographers need to use every tool of the trade to produce excellent images.

But then something else falls into place. Call it luck or serendipity, I don’t care. Our subject does something besides pose. I like to call it natural AND being prepared. We are patient, we persevere and are prepared for that moment. It just happens. Maybe not always, and not for long. And when it does, BANG, we got it!

I shot 52 images over 14 minutes of this bird from a blind in South Texas. Of all the frames of the roadrunner I shot, only two had something going on. I have many nice portraits- and some crazy poses. The light was nice, the weather great and the subject cooperative. But just for a moment, the bird spied the wasp and ate it in an instant. Then it left. That was all, but those two frames made a better story. I believe even much better than the full body portrait above. Judge for yourself. So- my suggestion is to keep your eye to the camera and be prepared. Don’t tire of waiting. The magic just may happen for you, too!

© Brian Loflin. All rights reserved.