field of view – What is the focal length on your typical cell phone camera?

Focal length does not change with sensor sizes – what actually changes is the field of view:

FOV (°) = 2 * arctan ( d (mm) / (2 * f (mm)) )

FOV is our field of view in degrees, d is one of the dimensions of the sensor (for diagonal, it is d = √(h² + w²) ) and f is the focal length in millimeters.

In very simple terms, a smaller sensors sees a smaller portion of the lens’s projection – e.g. a APS-C sensor does not fill out a 35mm lens’s image circle, so it cannot see the outer portions (which relate to the outer regions of the frame) and therefore, the field of view is narrower than it would be with a full frame camera.

When we talk about crop-factors, what we really are talking about is the change in field of view by a smaller sensor: The reference is a full frame sensor, which is 36*24mm. Therefore, a 10mm lens on an APS-C camera is still a 10mm lens – it just happens that it offers the same FOV as a 15mm lens would on a full frame camera.

The same of course is true for smartphones – unfortunately, the smartphone market is constantly and rapidly changing, and manufacturers usually do not state focal length or sensor size in their marketing texts, so research is needed on a per-phone-basis (or so I think).


A (at this moment) recent iPhone X offers an equivalent-to-28mm lens and an equivalent-to-52mm lens, the Samsung Galaxy S9+ offers 26/52mm, the OnePlus 6 offers 25mm, the Huawei P20 offers 27mm/80mm, the Nokia 6.1 offers 27mm,…

So it seems we can conclude that 26-28mm (equivalent) are a standard in Q3/2018.

sync – Super old email contacts suddenly appears in my phone contacts

When I woke up this morning I suddenly had 6 new contacts added to my contact book on my phone. All of them were emails, some of them I recognize from WAY back but I sure haven’t had contact with them in a LONG time. I guess they were added in some kind of sync activity, but I’m pretty sure none of these addresses that were added, is featured in any of the accounts I’m currently using (gmail, yahoo) etc. I had contact with these people way before this

Why did this happen?

Is there any way to find out where a specific contact were synced from?

data recovery – How can I get files off an Android phone without the ability to get into the phone?

I have a phone the touchscreen of which does not work, and so I can’t do anything like switching on debugging, or accepting notifications to share data, but the phone has no password and I can connect it to my computer without problems. How am I able to get photos, videos and notes off the phone without being able to use the screen? Thank you.

vpn – how to stop seeing ads from Taiwan on Instagram on my android mobil phone

I used VPN , turn off the mobile location, not log in with google account,RESET my mobile’s ads ID but there are still my country’s ads on instagram.

can anyone tell me how to stop seeing my country’s ads on my instagram, i can accept the VPN IP’ country’ ads.

thanks for your help!

How to proactively prevent data-theft if a stolen android phone is immediately taken offline?

  • Assume that it is an android 10+ and that it is encrypted.
  • Assume that it is protected by a 6-digit pseudo-random pin code.
  • Assume that the data can be erased remotely using google’s “Find My Device” service.

If the thief shuts the phone down, they’ll have to contend with the disk encryption (it will wipe itself after a certain number of incorrect tries)

If the thief doesn’t shut down the phone, they’ll have to bypass the lock screen before I am able to erase the data remotely.

If however, the thief simply places the phone in airplane mode (which doesn’t require a pin to access), then they’ll have unlimited time to bypass the lock screen.

  1. How likely are they to bypass the lock screen assuming little to no resources, fairly skilled, but hellbent on data extraction?
  2. Is there anything I can do proactively to not only make it harder for them to bypass the lock screen but also to prevent data-theft once/if they do.

The type of data I would be concerned about:

  • Email inbox.
  • Chat conversations (Skype; Whatsapp*; Slack).

I do have the option of removing said applications and data, but that would also make the phone largely useless to me.

  • Is especially tricky given that they’ll also have access to the sim card, and I am unlikely to be able to have it blocked/replaced somehow.

iphone – Phone calls immediately hang up – unless headphones are connected

Since updating to iOS 14.3 on my iPhone 7, incoming and outgoing phone calls immediately hang up with below error message, unless I have any bluetooth headset connected.

Call Failed

Everything works fine with a headset, though. As doing phone calls is kind of an important functionality in an uhm… phone, I would love to be able to restore the phone call feature.

What would be steps to try to fix this problem?