Some wide-angle lenses will exhibit barrel distortion, where parallel lines in the picture appear to bow outward, like a barrel. Many post-processing applications will have a tool to correct this. Pincushion, where parallel lines seem to bend inward, are more likely to be seen in telephoto lenses. Zoom lenses, especially cheaper ones, may suffer from both at either end of their range. I routinely use Lightroom Classic’s Lens Correction Tool on every processed picture inasmuch as I use zoom lenses almost exclusively.

I recalled an assignment from school intended to teach us how focal length and camera position affect spatial relationships in a 2-dimensional rendering of a 3-dimensional scene. I tried to duplicate that exercise.

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That has the effect of foreshortening the perspectives. The green jar only appears farther from the red because the camera has moved closer.

Many, if not most of you, have seen the so-called “distortions” incorrectly attributed to (blamed upon) focal lengths, most especially wide angle vs. telephoto.

5. Put the lowest magnification phase objective and corresponding phase annulus in place. For example, a 10x Ph1 objective with a Ph1 phase annulus.

As phase contrast microscopy does not require cells to be killed, fixed or stained, the technique enables living cells, usually in culture, to be visualised in their natural state. This means biological processes can be seen and recorded at high contrast and specimen detail can be observed. Fluorescence staining can be used in combination with phase contrast to further improve the visualisation of samples.

In photography, there is a curiosity often referred to as Perspective Compression. I use it instinctively, from decades of practice, but what exactly is it? Is it even a real thing? (It’s not.) Why would you want to learn about it?

The set below was made (extremely tediously working alone) by getting up and moving the camera closer for each frame, cropping in the camera. Compare the first, made at 105mm (equivalent to 158mm on a full-frame camera), with the bottom right, made at the lens’s shortest focal length of 18mm (27mm equivalent); you are seeing the misnamed “wide-angle ‘distortion’” from the camera being too close. The apparent warping is due simply to the lens being closer to my nose than my ears.

Neither jar moved in relation to the other; they are still the same sixteen inches apart on their centers, so why does the green jar appear to be receding further from the red?

Phase contrast microscopy translates small changes in the phase into changes in amplitude (brightness), which are then seen as differences in image contrast.

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I wanted to see if I could manage a portrait ringaround working alone. The first set of six below was made with the camera at a fixed distance. Only the focal lengths were changed. When the pictures were each enlarged to headshot size, you can see that the background objects did not change in relation to me or one another.

It is relatively simple and inexpensive to adapt an inverted or upright light microscope for phase contrast. The following components need to be installed:

So, if you’ve wondered why so many phone selfies look weird, it’s mainly due to their being held at arm's length, which is too close. Selfie sticks may not have been invented to make the perspective more pleasing, but they serve that function well.

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But barrel and pincushion are actual optical distortions within a lens. The “distortions” and “compressions” you hear about are not optical but illusionary. (Psssst, Bob, he sez we’re seein’ t’ings…)

What is phase contrast? Phase Contrast is a light microscopy technique used to enhance the contrast of images of transparent and colourless specimens. It enables visualisation of cells and cell components that would be difficult to see using an ordinary light microscope.

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What they don’t tell you is that every time you move the camera in any direction, you change the *perspective,* the perceived spatial relationships among all the elements in the picture, foreground to background.

Bbb-bb-but, you stammer; the far-away stuff looks closer when I use a telephoto. Yes, it does because longer lenses magnify everything in their field of view. The effect is not compression; it is foreshortening.

Phase contrast enables high contrast images to be produced by further increasing the difference of the light phase. It is this characteristic that enables background light to be separated from specimen diffracted light. The difference of the light phase is increased by slowing down (or advancing) the background light by a ¼ wavelength, with a phase plate just before the image plane. When the light is focused on the image plane, the diffracted and background light cause destructive (or constructive) interference which decreases (or increases) the brightness of the areas that contain the sample, in comparison to the background light.

Banner image: Confluente Rhabdomyosarcoma (RD) cell line under an inverted phase contrast microscope. Credit: Dhifaf zeki, Wikimedia Commons

Care must be taken with the condenser annulus and the phase rings, as they need to be matched in diameter and optically conjugated.

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Some of the light that passes through the specimen will not be diffracted (bright yellow in the picture). These light waves form a bright image on the rear aperture of the objective. The light waves that are diffracted by the specimen pass the diffracted plane and focus on the image plane only. This allows the background light and the diffracted light to be separated.

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Our instructors’ exercise taught us that we could prove the rule by cropping. We’d taken three photos, each with a wide-angle, a normal, and a telephoto, while not moving the camera on its tripod. The apparent spatial relationships with distant objects did not change, regardless of the lens.

If thicker samples need to be visualised in high-resolution, differential interference contrast (DIC) is a more suitable technique to use.

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9. Once all objectives have been aligned and centred, remove the phase contrast centring telescope and replace this with the eyepieces.

All of the components required for phase contrast need to be aligned and centred. Some phase sliders are pre-centred, we therefore recommend that you check beforehand. Details of how to centre and align phase components are below:

7. Using the adjustment screws on the condenser, centre the phase plate and phase ring so the segmented circle of light sits on the black ring.

Unstained specimens that do not absorb light are known as phase objects. This is because they slightly change the phase of light that is diffracted by them; the light is usually phase-shifted by about ¼ wavelength compared to the background light. Our eyes are unable to detect these slight phase differences as they can only detect variations in the frequency and intensity of light.

Conventional wisdom often suggests you don’t need zooms because you can “zoom with your feet.” ‘T’ain’t necessarily so, though, because moving the camera changes the spatial relationships among objects in your scene. You don’t even need a camera to see it; just look at any scene while moving left and right, closer and further, while watching the relationships in the scene. It might be an ah-ha moment for you.

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The banner picture above was made with my crop-sensor (APS-C) Sony A6400 fitted with a Sony E PZ 18–105mm f/4.0 G OSS (27–158 FF equivalent). The lens was at 105mm, ISO 200, 1.5-sec @ f/22. A crop factor of 1.5 from APS-C to full 36x24mm causes a 105mm to perform as if it were 158mm, a decent telephoto. We call them “telephotos” since they magnify like a telescope.

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Light from a tungsten-halogen lamp goes through the condenser annulus in the substage condenser before it reaches the specimen. This allows the specimen to be illuminated by parallel light that has been defocused.

1. If possible, set up Koehler illumination on your microscope. Read Scientifica’s 6 step guide to Koehler illumination to help you set this up.

You shouldn’t need to re-centre the phase contrast microscope. It is, however, recommended to regularly check that the set-up is centred using the phase contrast telescope.

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“Zooming with your feet” sounds reasonable. If you need to “zoom in,” just walk toward your subject until the finder is filled, easy-peasy. If you want more context in the frame, turn around and step further away.

These noticeable differences lead most photographers to believe that wide angle lenses are distorting a scene while telephoto lenses are compressing a scene, but they are overlooking what is actually happening: the camera is moving. In reality, the distance from the camera to the subject is what is creating these distortions. — Fstoppers

All of the components required for phase contrast need to be aligned and centred. Some phase sliders are pre-centred, we therefore recommend that you check beforehand. Details of how to centre and align phase components are below:

Photography is who I am. I can’t not photograph. I am compelled to write about the only thing I know. https://www.flickr.com/gp/43619751@N06/A7uT3T

I was an early adopter of zooms for professional work after burglars hit our studio one night and lifted my Nikon bodies and all their prime lenses. We were “between insurance,” so I had to replace them out of pocket. I chose the kit pictured above because it was what I could afford. I never looked back; been a confirmed Zoomie since 1986.

Phase contrast is ideal for thinner samples, therefore an inverted microscope system can be used. This provides the additional advantage of having more working space. Phase contrast can also be installed on upright microscopes.

It’s a common misconception that the apparent phenomenon of “perspective compression” — where distant objects in a scene look closer or further away from nearer objects — is affected by changing your focal length. Conventional wisdom and your own two enchanting Mark-1 eyeballs seem to support the notion that the longer the lens, the closer the far appears to the near.

The phase plate then changes the background light’s speed by ¼ wavelength. When the light is focused on the image plane, the diffracted and background light will cause destructive or constructive interference, which changes the brightness of the areas that contain the sample in comparison to the background light. Often the background is also dimmed by 60 to 90% by a grey filter ring.

The only changes were the focal length and the crop. If you try this you’ll probably get lots of grain (noise) the more you enlarge, but most post-processing apps should have de-noising tools built in. All these pictures are unretouched.