# Camera Calculator Manual Entry Of Distance And Width

After adding a camera to the map in Camera Calculator, can I manually enter the distance and width or can that only be done by dragging the handles on the camera triangle? When I attempt to enter the distance and width manually, entering one causes the other to change. I've clearly overlooked something in the tutorials on how to have the calculator automatically work out the focal length and angle of view when manually entering the distance and width but I haven't figured it out yet. I'd greatly appreciate some tips.

I believe there use to be a few links to ancillary calculators at the bottom of the page.

One said something like:

How far can this camera see?

And would let you solve for focal length. I don't see them anymore though on the page.

Regarding what changes what in the 8 values in the calculator:

Of the three drop downs:

Resolution changes only PPF

Imager Size changes everything except for Distance

Unit changes Distance, Width and PPM/F (really just the UOM is changing)

Changing any of the 5 entry fields, (Focal Length, AOV, Distance, Width, and PPM/F) will affect all others with two big exceptions:

1. Entry fields on right never affect ones on left.
2. Entry fields on left never affect Distance.

One thing discussed a long time ago when this was brought up was possibly being able to "lock" down whatever values one wanted and then the data would pivot around those constants.

Thank you Undisclosed 1 for your insight. What you've said matches my observations. What I'd really like is to be able to enter the distance, width and camera resolution and have the remaining fields update accordingly.

Luke, 1, thanks.

You probably notice that when you update the width or length, the AoV / focal length stays the same but the other one changes (i.e. change width, length changes, change length, width changes).

I think it makes more sense to do what you ask, i.e., if you change width, length stays constant, but AoV / focal length changes.

I want to check with our lead developer first in case I am missing any other elements that might be negatively impacted but I see what you asking for as being more natural. I'll update this later today.

Wonderful! Thanks very much John.

So has the Lindgren Lens Selector been officially retired?

The code is still available, we are just not displaying the other modes. We might add them back in another view or tool. Not sure. You're the first and only person to mention it since we removed it months ago.

You're the first and only person to mention it since we removed it months ago.

Actually I wouldn't have even mentioned it except that it would have worked for Luke in this case, if I'm not mistaken. And unless someone had used it in the past they wouldn't even know to ask, since the primary calculator appears to have the necessary fields; though I think it is not ideal for solving certain "what ifs" because of its superfluidity.

At the end of the day and IMHO, whichever parameter you make dependent, there will always be a problem with the one of the use cases.

A simple example:

You want to see the effect that varying the PPF has on the distance.

You want to see the effect that varying the PPF has on the focal length.

Both I believe are valid use cases, but both cannot be accomadated with a fixed dependence formula.

On the other hand, if one were able to lock a parameter down, by say double clicking the field, then one would be able to see the desired "what" for a given "if". When a field is locked down, it could have a little icon showing this.

As a practical matter, when you are inputting 2 values and the first one you have put in unexpectedly changes when you input the second, it's discouraging.

I understand your desire for a single stateless tool, but requiring one to understand the dependencies in the calculation is IMHO, burdensome.

Though it's still awesome either way. :)

We are not adding a lock for parameters, it would cause more confusion for basic users.

Ok. But just to be clear, nothing would change for a basic user. It would just be an additional thing you could do (dbl click on the field) when a parameter won't stay still.

And if someone mistakenly double clicks, and does not realize they are in a different mode, problems ensue.

We're going to change the operation discussed herein, and we can revaluate after that.

Confirmed: we will switch operation to allow width and length to be changed without impacting the other (as discussed above).

There is one condition we then need to address. When selecting specific camera models, cameras with integrated lenses (whether fixed or varifocal) cannot support any combination of length and width. For example, a camera with a fixed 80° AoV at any specific distance, will only support one width. As such, entering in 10 for distance and 100 for width cannot work. Right now, if someone enters 100' width for a fixed 80° AoV, we just change the distance to match.

So how do we handle changing width and length for cameras with integrated lenses for combinations of width and length the camera cannot support?

Will there be a way to change PPF and see a change in focal length?

Again, we are choosing one or the other. Right now, changing PPF keeps AoV / focal length constant and changes width and distance. It would be better to simply reverse it, to be consistent with the above proposed change.