If you prefer to read in PDF file on your computer, you can download it here. Both free and paid version of The Photographer’s Field Tools are available on Google Play Store. Here is the QR code that leads you directly to the Play Store which you can scan using your Android phone.


Ansel Adams dedicates the beginning of his first book “Taos Pueblo” to visualization. He introduced the idea of “previsualization”, which involved the photographer imagining what he wanted his final print to look like before he even took the shot. Of course there are many great photos which were taken impromptu. However, photographers tend to previsualize the scene before they go there, which will greatly increase the chance of getting better shots. In the other words, they already decided where to go to the best view, at what time of the day, with what kind of lens and filters, etc. Even with very careful preparations, many photographers had to go to the same place several times simply because the light or the cloud doesn’t cooperate. That’s why I started to think if there are anything that I can do to make the preparation easier and more productive for photographers.

Photographers use various tools to help them pre-visualizing the scene. Nowadays, many of those tools are phone apps. For example, the famous TPE app can be helpful visualizing the Sun and Moon location at a giving time and location.  A star map app can be used to predict where the Milky Way is. A map such as the Google Map can also be used to determine geographic characters surround the scene. This Photographer’s Field Tools (or PFT in short) is designed to leverage the Google Map to provide the necessary tools for photographers to pre-visualize the scene. Some questions that you might ask yourself before going out for a photographing trip are:

  • Where should I go to get a nice view of the subject?
  • How far am I from the subject?
  • What angle will I look at my subject at?
  • Do I get a clear view of it?
  • What lens should I bring?
  • Can I get the composition I want using one lens or will I have to take multiple shots and stitch them together?
  • With the help of other apps such as TPE or Star Map, will the Sun, the Moon or the Milky Way in my composition?

You will get answers for all those questions after you finish reading this tutorial.

The Map

The center of this app is a Google Map. You can show the Google Map in a normal Map mode, the Satellite mode, or the Terrain mode. You can search on the map to help you finding a location. The app can also accept the shared text information from other apps such as the Google Map app. Once the map shows the area that contains all the interesting locations for a particular scene, the next step is to bring out the actual tools by selecting the wrench icon on the action bar. Note that the action buttons could be on top or on bottom depending the phone orientation.

Hint: I usually long press on the map to lock the map so that when I move the tools that are overlaid on the map, I won’t accidently move the map.

Location and Distance

The first two tools in this app is the Location tool and the Distance tool.

The location tool is really simple. See below. You can drag the scene icon to any location, the tool will tell you the exact GPS coordinates and optionally the elevation. You can share it to any app you want – email yourself, save to Evernote, copy to clipboard. Sometimes I went to a special place, I want to keep the GPS location. To my surprise, the Google Map app doesn’t have a way to find out the GPS coordinates. Now with this tool, you can do it.

Half Dome - Location

Hint: I usually switch to Terrain map view for mountains so that I can easily find the highest point easier with the help of the contour lines.

Hint: I usually “pin” down the scene icon by selecting the “Pin the Scene” action from the action bar. Or I use “Add Marker” feature to add a couple of markers around the area so that I know the boundary of the subject. Once zoom out, I may not be able to see the subject clearly but the markers will still be visible at any zoom levels. See below for an example where I marked the Vernal Fall, the Nevada Fall, the Half Dome peak and sides in the map so that later I can see them when selecting the angle of the view from the Glacier Point.

Markers - Glacier Point

The Distance tool uses two locations. See below. It will measure the distance from the camera location to the scene location, and optionally, the elevation gain (or loss if negative). It is basically a map ruler that can measure the direct distance between the two points on the map. Please note, the distance is the direct distance on the Earth surface. It is not a walking or driving distance.

Half Dome - Distance

The elevation gain feature is an interesting one. For example, you want to know what happen if you drop from the north face of the Half Dome by accident? Well, don’t even think about it. As you can see below, it is a sudden vertical drop of over 800m or 2600 ft. How deep is that? Empire State Building is only about 400m.

Half Dome - Elevation Gain

If you enable the Elevation Details option in the preference screen, you will also be able see the elevation details in color. See below.

Half Dome - Clear   Half Dome - Clear - Details

As you can see, the line between the camera and the scene is color coded. Green means there is a large clearance to the ground. The more yellowish, the less the clearance. Red means no clearance at all. In the other word, if you see a red section along the line, especially near the camera, it means something is blocking the view. With the help of this feature, you can easily decide where to go to get a clear view of the subject.

I remember I hiked up to the Upper Yosemite Fall, hoping to have a closer view to the Half Dome. I was disappointed. It was blocked by another dome where the Yosemite Point is. You can see that on the picture above. You will have to hike another mile or two to the Yosemite Point, or even further to North Dome, to see the whole Half Dome. Actually, one of the best views to the Half Dome along the Upper Yosemite Trail is at the Columbia Rock. See the two pictures below where show the colored line from Yosemite Point and the Columbia Rock to the Half Dome respectively.

Yosemite Point - Clear   Columbia Rock   

Note the algorithm of the Elevation Details feature is designed based on the assumption that the Earth is a sphere. As we all know, it is just a mathematic model. The actual Earth is not. In the other word, the result of this feature is not 100% accurate (but very close to 100%). But if you find the result from the elevation details doesn’t match with the actual result on the field, please use the share feature to share the result with us. We will take a look and find ways to improve our calculation algorithm.

The other thing to be noted is the elevation data doesn’t consider any human-make elements such as buildings or some other natural elements such as trees. The view could be blocked by a tree or a building even when the PFT says it has a clear view. In this case, you just need to zoom in to the Satellite view of the map to see if there are any tall objects near the camera location to avoid surprises on the field.

As you can see, the first two tools are not just for photographers. Any person who like to travel will find them useful. But photographers will make the most of them when scouting the scene at home or on the field. It is like a step by step process. First, you identify the scene you want to take the shot (thus represented by a scene icon). Secondly, you decide where you will put your camera (thus the camera icon).  Once the two locations are decided, you will do more research of the scene using the other tools we provided.

Focal Length

What lens to bring is a question that all photographers will ask themselves before going out for a trip. Sometimes, it is a tough question. Bringing them all is an easy answer but not an easy decision for a strenuous long hiking.

Before I went to the famous horseshoe bend near Page, AZ for the first time, I searched on flickr to see the pictures took by other photographers. That’s how I figured out a 17mm super wide angle lens will capture the whole bend. It doesn’t always work. First, the picture could be cropped or stitched which I can’t tell. Secondly, if you are a pioneer who explore an area that there aren’t any existing photos, or you want to capture using a different composition, you will have to figure it out the focal length yourself.

With PFT’s Horizontal Focal Length Tool, I can easily figure out the focal length if have a composition in mind. As you can see below, the horseshoe bend is indeed pretty wide but luckily in the range of the common super-wide lenses such as 17-40 or 16-35. The transparent green area is the angle of view. The two green lines can be dragged. You can drag them to adjust the angle of view. Or you can drag between the two lines to drag the whole view without changing the angle. The camera rotate icon on the action bar allows you to toggle between the landscape and the portrait orientation. Portrait orientation will request a smaller focal length for the same angle of view. We calculate the focal length based on the sensor size of your camera. By default, 36x24mm full frame sensor is used. You can adjust it in the preference screen. The eye icon on the action bar allows you to select a focal length instead of using finger dragging which sometimes is hard to get the exact focal length you want.

Horseshoe Bend - Focal Length

See below for another example of the focal length tool. The camera icon is at the Skylon Tower at the Canada side of the Niagara Falls. If you want to capture both the America Fall and the Horseshoe Fall, you would need a super wide lens. I wish I had a 14-24 lens. Canon, when are you going to release one?

Niagara Falls - Focal Length Vertical - Landscape

Focal Length (Vertical)

The focal length tool we just covered can help visualize the scene horizontally. What if the subject is very tall? That’s the PFT’s next tool for – the Vertical Focal Length Tool.

Let’s say you want to take a picture of GE Building at the Rockefeller Center. It is 260m tall. At this height, it is very hard to take a picture to include the whole building. If standing too close to it, the angle of view is way too wide. If walking away from it, then usually some other buildings are in the way. Luckily, on the east side of the GE Building, there is an opening which takes you about 100m away from the building without any obstacles in between. Now let’s pre-visualize it. See below.

Rockefeller Center - Focal Length Vertical

I put the camera icon at the location which is about 128m away from the GE Building. I will hold the camera in portrait mode, then I drag the upper green line until the “above” value should a number larger than 260m. I could also drag the lower green line down a little bit in case there are some interesting foregrounds that I want to include in the picture. The focal length tells me it is 22mm. As you can see, this composition is still pretty tight. I would certainly try to bring a 17mm or wider lens there to take such a shot. As you can see, by pre-visualizing the scene, you are much better prepared.

Let’s see another example.

I have to confess that I have never been to this location before, though I had planned it for a long time for my northern California and Oregon trip. I would like the snow-covered Mt. Shasta with some sky/clouds as the background, together covering the top 1/3 of the frame; the Lake Siskiyou as foreground, covering the bottom 2/3 of the frame. Hopefully I could find some interesting plants or stones along the lake and use them as near-foreground. To be more specific, the top 1/6 is sky/cloud, next 1/6 is Mt. Shasta, the next 1/3 is the reflection of the sky and the mountain in the lake, the last 1/3 is the lake with some interesting foreground. That’s what I am pre-visualizing in my mind. I am interested to find out what kind of lens I should use to capture such a composition. Now let me explain how this composition can be pre-visualized in the Vertical Focal Length Tool.

First of all, I search for Mt. Shasta, put a marker on it or pin the scene icon on it. Secondly I zoom in to find the Lake Siskiyou to locate an open beach. I will use the elevation details feature in the Distance tool to make sure I have a clear view to the Mt. Shasta. Once finding such a location, I pin down the camera icon. Now I will zoom out so that I can see both Mt. Shasta and Lake Siskiyou on the screen.

Hint: You can not only zoom the map but also can rotate the map. I usually prefer to rotate so that the scene and the camera are at the same or close to same horizontal level.

Mt Shasta - Focal Length Vertical - Portrait

Now I can long press on the map to lock the map. Switch to the Vertical Focal Length Tool if you haven’t. It tells the elevation difference is 3.25 km. That’s the relative height of the Mt. Shasta. It also tells me the angle is 9 degree. Because when we look at something, the view plane is actually a sphere. It means the Mt. Shasta will cover 9 degree of the viewport. As I also want to include some sky which is about the same height as the mountain, I drag the top green line so that the “above” value shows about 18 degree which is two times of 9 degree. You can also use 2 times the height. At such a small angle, the difference won’t be a big deal. Because the angle above the horizon is 18 degree, I drag the bottom green line so that the angle below the horizon is 38 degree which is again about 2 times the angle above. This settings will make sure the composition is 1/3 for the mountain and 2/3 for the lake which is exactly what I visualized. I also would hold the camera in portrait orientation so I click on the Focal Length label to toggle the orientation. As you can see from the screenshot above, the focal length is 32.9mm in this case.

Sometimes you want to go back and forth between the Horizontal Focal Length and the Vertical Focal Length to make sure the selected focal length will cover the scene both vertically and horizontally. In this case, because the Mt. Shasta is a volcanic mountain (a volcanic mountain is usually vey wide/flat), you certainly want to check the horizontal focal length to make sure it is okay to cover the whole mountain. See below. It looks like at 33mm focal length, it can cover the whole Mt. Shasta without any problem. Now I know, for sure before I even go there, that my 24-70 standard lens will work for this composition. I am looking forward to go there in person now.

Mt Shasta - Focal Length Horizontal

The example above is an example of good location. In many other cases, this tool might tell you the composition doesn’t work because of no clear view, or the angle of view is way too large or way to small. That’s exact purpose of this tool so that you pre-screen locations and rule out bad ones. You will soon find you drag the camera icon all over the place in order to find a location.

In the Vertical Focal Length Tool, we can also use the Elevation Details feature. Once you enable it in the preference screen, you will see the two green lines that can be dragged is now color coded. See below. While the line is being dragged, the color will change immediately to reflect the details of the elevation. As you can see below, while the whole angle of view of Mt. Shasta above the horizon is 9.9 degree, it was blocked at 2.3 degree by a small hill near the lake. I suggest you use Vertical Focal Length Tool along with the Distance. The Distance Tool only tells if you can see the subject directly. When the subject is the peak of a mountain, can you see some slope as well or just the peak itself? It won’t tell you. On the other hand, the Vertical Focal Length Tool will tell you how wide the angle of view is to the subject.

Mt Shasta - View at Low Angle

Depth of Field

Let’s take the Mt. Shasta example further. I mentioned I want to take some plants or lake stones or boats as foreground in that composition. Obviously I want both the foreground (plants, stone, or boats) and the background (the mountain) in focus. In photographer’s term, that’s a larger depth of field. Now let’s switch to the Depth of Field Tool. Without adjusting anything on the screen, the tool tells me at f/8, the DoF is from 4.45m to infinite. It means if the foreground object is further than 4.45m, it will be reasonable sharp if the camera focuses on the Mt. Shasta. What if the foreground is closer than 4.45m? You have two choices. Luckily, you can find out whether either of the two choices works in this tool.

Mt Shasta - DOF - f8

The first choice is to focus at the hyperfocal distance instead of at the Mt. Shasta. As you can see from the last row “Maximum DoF” which is from 2.24m to infinite. That’s the DoF if you focus on the hyperfocal distance of 4.48m. It means everything from 2.24m to infinite (including the Mt. Shasta) will be in good focus if you focus at 4.51m. You want to know where is 4.51m? Just pin the camera icon first if you haven’t then select center on the camera and zoom all the way in. We draw a dark arc at the hyperfocal distance.

Mt Shasta - DOF - f8 - Near

The second choice is to reduce the aperture. You can click on the Aperture icon on the action bar to select a different aperture. For example, you use f/16, the DoF is increased to 2.22m to infinite. If you again focus on the hyperfocal distance, the DoF is further increased to 1.13m to infinite. See below. Please note, we only allow you to select some apertures as cameras don’t support any random apertures. You can change in the preference screen to select the minimum aperture and the stop between the apertures to match with your camera and lens.

Mt Shasta - DOF - f16

It looks like either choice will cover any foreground that is further than 2.2m. If the foregound is even closer but you don’t want reduce the aperture, then you will have to take multiple pictures – one focus at the Mt. Shasta, the other focus on the foreground, then do focus stacking in the post-process.

Actually, DoF Tool also allows you to mimic the DoF for different focus distances. if you further zoom in on the map at the camera location, you will see the DoF tool will show the hyperfocal distance visually on the map. See below. Now if you unpin the scene icon and drag it (which is now indicates the focus point on the map), you will see the DoF (represented by the green area) changes. It means if you focus on the distance represented by the scene icon, any objects in the green area are in focus.

Lake Siskiyou - Dof- Near

Without Google Map

The PFT works without the Google Map too. You might acquire a map from somewhere else. For example, you took a picture of the map at the entrance of a national park, or from computer screen, or you save the map image from web. As long as the map is proportionally scaled, you can use the map image as background to replace the default Google Map. Obviously, not all tools will work for a map image because the map image doesn’t contain the GPS location and the scale information. The only tool that works in the current release is the Horizontal Focal Length Tool. In the future releases, we will let you input the scale information manually so that we can make Vertical Focal Length Tool and DoF available for the map image.

See below for an example where I took a picture of a detailed Yosemite Valley map and use it as background. The camera is at the Sentinel Bridge. If you want to take a nice detailed picture of the Half Dome from there, the tool tells you that you would need an 85mm telephoto lens.

Yosemite Valley Picture Map - Focal Length


At any time, you can press the Menu – Share to share the information displayed on the screen to another app. There are many apps you can share to as you can see below.

Share     Tweeter Share

The information to be shared is text only. We are working on a solution to share the picture. Right now because the Google Map doesn’t allow us to capture its map image, we haven’t found a solution other than root your device. For now, there is a two-step workaround if your phone allows you to capture the screenshot. I know on the Samsung Galaxy S3 and later, you can put your palm side way over the screen and slide from one side to the other side to capture the screenshot. If you have an ICS (Android 4.0) phones, you can capture a screenshot by holding down the Power button (top left) and the capacitive Home key (bottom right) or the Volume down button (right spine)  until you hear the camera shutter sound and see an animation onscreen. Some Sony phones can take a screenshot by pressing the power button which will show a selection to take screenshot. There are also apps on the Play Store allowing you to capture the screen. Most of them require a rooted phone. In any case, you may want to lock the screen first before taking the screenshot. Once you have the screenshot, just click on the share menu to bring up the app you want to share with, add the screenshot along with the text. See the above image on the right. I shared it on twitter with both text and picture.


You can press Menu – Preference to go the preference.



The Location, Distance and the Vertical Focal Length Tools leverage the elevation. For now, we get the elevation data using the Google Elevation API or the Bing Map API. The Google Elevation API is free but it unfortunately has a daily quota of 2500 requests and 25000 samples. The Bing Map API requires a Bing Map Key. You can apply a Basic Map Key for mobile apps for free at http://www.bingmapsportal.com/.

To avoid over usage of the elevation, we included two options in the preference screen.

The first option “Elevation Service” is to show or not show any elevation at all.

The second option is “Elevation Details”. We used it to figure out if there is a direct view from the camera to the subject and color coded the line in between. Because it will sample many points along the line, it downloads a lot more data than just the elevation of two points. Be cautious if you are using cellular data.

Furthermore, we will never request the elevation data unless you tap on the label which says “touch to update”. The preference screen will also show you how many requests have been made so far.

Trust me, the Google Elevation API quota limitation is real, not a myth. We will show you a message when it happened. See below. When that happened, please turn off the “Elevation Service” option completely or switch to Bing from the preference screen. You will have to wait 24 hours before you can use the elevation service from Google again.

Camera Type

You can select your camera type in the preference screen. We don’t really care what camera you have but to calculate the focal length and depth of field, we need to know the sensor size and circle of confusion (CoC). That’s we choose a few common cameras that you can select as we know the sensor size and CoC for those cameras.

Camera Types

If your camera is not in the list, just choose Custom Sensor in the camera type and enter the sensor size and CoC yourself. The two wiki links below have a pretty wide selection of cameras.


(Note: for 35mm full frame camera, the wiki of CoC listed the CoC as 0.029mm but on Canon and most other websites, it is 0.03mm. That’s why in this app, we use 0.03mm)

Supported Devices

The PFT supports any Android phones that have Android version of 3.0.x or above. That means it includes Honeycomb, Ice Cream Sandwich and Jelly Bean.

Old versions, such as Gingerbread, Froyo, Eclair, Donut and Cupcake, are not supported. Gingerbread is the only version that currently still have a large percentage. If you are still on Gingerbread and would like to use PFT, please email us to let us know. If we receive many requests, we will consider porting PFT to Gingerbread.

PFT supports both phones and tablets.

Network connection is required to use the PFT if you want to use the map. I’ve noticed sometimes the cached map is used when there is no connection so PFT can still be used to certain extend. However, searching, elevation etc. features definitely require network connection. The Google Map app has a way to support the offline map but I don’t think this feature is exposed to other 3rd party apps. Using another map source remains as an option for future. The picture mode will always work without the network connection.

Because Android has so many versions and devices, we can’t claim all devices will work. If PFT doesn’t work on your phone, please email us to let us know.

Our support email is yingwentech@gmail.com.