如何拍攝紫外線激發(fā)的熒光照片？

How to Capture Ultraviolet-Induced Fluorescence (UVIF) Photos

當(dāng)物體中的分子被高能紫外線波長（來自我們的紫外線手電筒）激發(fā)（激發(fā)），能夠發(fā)射出可見光（紅色、綠色和藍(lán)色）時，就會發(fā)生紫外線誘導(dǎo)熒光（UVIF）。這些發(fā)射的較長波長的光線就是我們需要拍攝的熒光。

Ultraviolet-induced fluorescence (UVIF) occurs when molecules in an object are excited (energized) by high-energy ultraviolet wavelengths (from our UV flashlight) and as a result, emit longer wavelengths in the visible portion of the spectrum (red, green, and blue). These emitted longer wavelengths are what we are photographing.

警告：紫外線會對眼睛和皮膚造成嚴(yán)重傷害。使用紫外線燈時，務(wù)必佩戴適當(dāng)?shù)淖贤饩€防護(hù)用品。切勿直視紫外線光源。

首先，找一個完全黑暗的地方，在那里你可以安裝相機(jī)和三腳架。這個區(qū)域應(yīng)該有一張桌子或長凳來支撐拍攝的物品。

Warning: Ultraviolet (UV) light can cause serious damage to the eyes and skin. Always wear appropriate UV protection when using UV lights. Never look directly at a UV light source.

First, find a completely dark location where you can set up a camera and tripod. This area should have a desk or bench to support the item being photographed.

如果你想像我這樣拍攝熒光照片，你需要訂購一個紫外線手電筒，你的手電筒應(yīng)該發(fā)射365納米的紫外線。我使用的紫外線手電筒是我在xepu.cn上購買的一個22美元的簡單迷你紫外線手電筒（XEPU-1530B 365nm迷你手持手電筒）。

拿起一個小的LED手電筒，在大約5500 K（正常日光）下發(fā)光。這個手電筒將用于創(chuàng)建您的自然顏色參考圖像。

一旦你拿到了紫外線手電筒，等到晚上，再去尋找能發(fā)出365納米紫外線熒光的物品?？纯茨闼诘貐^(qū)的花、植物、巖石或地衣，看看什么看起來很有趣。一些人造物品也會發(fā)出熒光，所以看看你的房子周圍，看看你能找到什么。

Order a UV flashlight. If you want to record images like the ones I have created, your flashlight should emit UV light at 365 nanometers (nm). The UV flashlight I used was  Fluorescence Flashlight purchased on xepu.us (the XEPU-1530B 365nm Mini Handheld Torch).

Pick up a small LED flashlight that emits light at about 5500 K (normal daylight). This flashlight will be used to create your natural color reference images.

Once your UV flashlight arrives, wait until the evening or night and go searching for items that fluoresce with 365 nm UV light. Look at flowers, plants, rocks, or lichen in your area to see what looks interesting. Some man-made items also fluoresce so take a look around your house and see what you can find.

收集一些物品，把它們帶到你的黑暗區(qū)域。

將相機(jī)和三腳架放在桌子或長凳附近，將一件物品放在干凈的黑色表面上。我用了一塊黑色的泡沫芯，但任何不會發(fā)出熒光的東西都可以。

關(guān)閉房間的燈，用紫外線手電筒照亮物體，看看哪些部位值得拍照。把房間的燈重新打開。

Collect a few items and bring them into your dark area.

Set up your camera and tripod near the table or bench and place one item on a clean black surface. I used a black piece of foam-core but anything that won’t fluoresce will work.

Turn off the room lights and illuminate the object with your UV flashlight to see what parts are interesting to photograph. Turn the room lights back on.

放置物品、相機(jī)和鏡頭，使感興趣的區(qū)域充滿框架。我在數(shù)碼單反上使用了100毫米微距鏡頭，效果很好。

關(guān)閉相機(jī)的自動對焦系統(tǒng)，手動對焦對象（相機(jī)在黑暗中不會對焦）。

將相機(jī)的“白平衡”設(shè)置為“日光”設(shè)置或5500 K（不要使用“自動白平衡”）。

如果可以的話，請將相機(jī)設(shè)置為錄制RAW圖像；這將為您提供盡可能好的圖像質(zhì)量。如果您的相機(jī)只能記錄JPG圖像，請將其設(shè)置為高質(zhì)量。

將相機(jī)設(shè)置為在手動曝光模式下錄制圖像。

將您的鏡頭光圈設(shè)置為一個值，該值將為您提供所需的景深。我使用了F22的設(shè)置來增加景深，但你可以選擇任何你想要的值。F值越高，曝光時間就越長。

將快門速度設(shè)置為20秒。這是一個很好的起點，但一旦你熟悉了曝光需要多長時間，你就可以改變它。你可以打開快門，然后通過調(diào)整打開手電筒的時間來控制曝光。

Position the item, camera, and lens so the area of interest fills the frame. I used a 100 mm macro lens on my DSLR which worked quite well.

Turn off your camera’s Auto Focus system and focus on the object manually (your camera won’t focus in the dark).

Set your camera’s White Balance to the Daylight setting or 5500 K (do not use Auto White Balance).

Set your camera to record RAW images if it is capable of doing so; this will give you the best image quality possible. If your camera can only record JPG images, set it to the highest quality setting.

Set your camera to record images in Manual exposure mode.

Set your lens aperture to a value that will give you the amount of depth of field you need. I used a setting of F22 for increased depth of field but you can choose any value you wish. The higher the F value, the longer the exposure will be.

Set the shutter speed to 20 seconds. This is a good starting point but you can change it once you become familiar with how long the exposures will need to be. You can leave the shutter open and then control the exposure by adjusting the length of time you have the flashlight turned on.

將相機(jī)的ISO設(shè)置設(shè)置為1000。這是一個很好的起點，但一旦你熟悉了程序，你就可以改變它。

設(shè)置相機(jī)，使其顯示記錄圖像的直方圖。當(dāng)你在黑暗的房間里時，圖像通常會在相機(jī)的顯示屏上顯示得更亮，所以直方圖會顯示你是否真的有很好的曝光。

使用電纜開關(guān)觸發(fā)快門，或者使用相機(jī)的自拍器并將其設(shè)置為2秒延遲。

檢查以確保您的對象仍在畫框中并處于焦點中。

關(guān)閉房間的燈并啟動攝像頭。

Set your camera’s ISO setting to 1000. This is a good starting point but you can change it once you become familiar with the procedure.

Set up the camera so it shows the recorded image’s histogram. Images often appear much brighter in the camera’s display when you are in a dark room so the histogram will show you if you actually have a good exposure.

Use a cable switch to trigger the shutter or use the camera’s self-timer and set it for a 2-second delay.

Check to make sure your object is still in frame and in focus.

Turn off the room lights and trigger the camera.

Once the shutter is open, turn on the daylight-balanced flashlight and illuminate the object from different angles. I use a smooth arc motion around the front of the object so as to decrease the likelihood of shadows in the object. Note how long you illuminate the object and from what distance. You can alter both illumination time and distance to increase or decrease the image exposure.

Check the image histogram to determine if you need to increase or decrease the exposure.

Record another image making changes in your lighting technique. It will take a few tries to create a good exposure so be patient and try different distances and flashlight duration times.

After you have recorded a good natural color image, you are ready to record your Ultraviolet Induced Fluorescence image.

Don’t move the camera or change the focus.

Record your UV image in a similar fashion as the previous natural color image except this time use the UV flashlight to illuminate the object.

Check the histogram to make sure you have a good exposure. The UV exposure time will probably be different than your natural color exposure.

Once you have an image you are happy with, check the focus of both the natural color and UV images to make sure they are both sharp.

Repeat this process for all the objects you wish to photograph.

Note: Some UV lights also emit a fair amount of blue light and some sensors are sensitive to UV light so if you wish to only record pure induced fluorescence you will need to place a UV absorption filter in front of the camera’s lens to block the wavelengths coming from the UV lamp. I didn't use any filters for these images.

That’s it! Hopefully this guide was helpful as you take your first steps into the world of ultraviolet-induced fluorescence photography!