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In microscopy, why does viewing specimens directly through the eyepieces with one’s eyes produce superior image quality compared to capturing them with a digital camera? - Tips and tricks for improving the quality of your microscope images

When a specimen is observed through the eyepiece of a microscope, the image is often perceived as being of better quality than an image captured with a digital camera attached to the microscope’s photo port. This is because the human eye is able to dynamically adjust and capture details at a resolution that is far beyond the capabilities of most camera sensors.

Here are some useful tricks that will help you improve the quality of your microscope images. 

Why does the human eye outperform cameras?

Unlike a camera’s fixed, static sensor, the human eye is able to dynamically adjust to varying levels of light and focus, significantly enhancing the quality of images seen through a microscope.

• The human eye can perceive an enormous dynamic range, capturing the tiniest differences in brightness, colour and contrast. Even the most advanced digital cameras don’t even come close to replicating this capability.
• Focus and accommodation: The human eye is able to adjust its focus for objects at different distances and to track objects moving in depth. This process is controlled by the ciliary muscle, which changes the shape of the elastic lens, allowing the eye to bring both near and distant objects into focus. This results in the perception of greater depth of field when looking through the eyepiece, with the entire field of view appearing in focus.
• Unparalleled resolution of the human eye: The human eye has its highest resolution at the fovea, the central part of the retina, while resolution decreases with distance from the fovea (peripheral vision). The brain constantly moves the eyes to build a complete, high-resolution representation of what we see. This is equivalent to about 500 megapixels of camera resolution.
• The iris of the human eye acts as a dynamic aperture, adjusting the amount of light that enters the eye. In good lighting conditions, when looking through a microscope, the iris contracts and blocks peripheral rays of lights from reaching the retina, which is comparable to the image sensor of a camera. This aperture mechanism contributes to error correction, thereby enhancing the overall image quality.
• Error correction: The human eye’s optical system corrects for many of the chromatic and spherical aberrations (colour and focal errors) caused by the microscope. Cameras, however, capture these errors without filter.

What can I do to improve the quality of my microscope images?

• Eliminate aberrations throughout the entire optical system of your microscope setup: The most effective way to do this is by using high-quality microscopes. The quality of the microscope objectives also plays a crucial role in image quality. Objectives with plan apochromatic correction and high resolving power (numerical aperture, NA) are the best choice and deliver superior image quality. High-grade microscope adapter solutions are another key factor.
• Aim for an optical alignment of the image observed through the eyepiece with that of the phototube (parfocality). For optimum quality, the phototube should be aligned (made parfocal) with the eyepiece tube. The image seen through the eyepieces and the image seen by the camera attached to the phototube should be in focus at the same time. Small deviations have little impact on image quality. However, if the camera display shows a totally blurry image and requires extensive refocusing using the microscope’s micrometer screw, this indicates a mismatch or incorrect settings of the adapter solution. There is a risk that the objectives are not operating at the optimal working distance from the specimen, leading to suboptimal image quality and increased optical errors. LM microscope adapters are designed to match the respective microscope models. We also offer specialised adapter solutions that allow for individual focus alignment. These are marked as “focusable” in the product description.
• Selecting the right microscope: Conventional Greenough-type stereo microscopes are mainly designed for visual observation through the eyepieces. The two separate optical paths create a three-dimensional image in the brain. When capturing an image, only one of these paths is used, which reaches the specimen at an angle. For this reason, these microscopes aren’t the prime choice for high-quality photography applications. However, with a few tricks it is possible to significantly enhance the image quality.
• Use optical systems with a central optical path for photography applications. These usually deliver the best image quality.
• Use microscope objectives with a high numerical aperture (NA), because they offer superior resolving power. Typical characteristics are their large lens diameter and short working distance.
• Choose the right digital camera: The image sensor should deliver a wide dynamic range and high light sensitivity.
• Enhance dynamic performance by using HDR mode: HDR mode captures multiple images at different exposures and automatically combines them into a single image with better dynamic range, either in-camera or with a specialised software.
• Optimise your lighting system: Lighting is a key aspect in creating high-quality images. A good lighting system ensures a uniform field of illumination with sufficient light intensity.
• Avoid motion blur: Motion blur is one of the most common blurs that degrade microscope images. To sidestep this issue, it is advisable to trigger your shots remotely, either with a dedicated remote shutter release or through software from the computer. Try to avoid any vibrations during the exposure process.
• Use the magnifying function of the digital camera or the remote camera control software for optimal focus. Because the camera display has fewer pixels than the image sensor, it is particularly important to use the magnifying function (5x, 10x, 15x, etc.) for focusing precisely on the desired detail or level.
• Improve depth of field with a focus stacking software: Multiple images are taken at different focus distances and combined into a stack, which is then processed with a special software tool to create one perfect composite image. In professional settings, photographers often use motorised focusing rails to automatically create a stack of more than 100 individual images, which are then merged into a single, highly detailed image with a greater depth of field.
   

If you have any questions on this subject, please do not hesitate to contact us. We are happy to provide advice!