Telephoto zoom cameras are awesome, but not as awesome as you think

Telephoto zoom cameras are awesome, but not as awesome as you think
In 2016, phones with more than one rear camera were a rarity. In 2019, it is hard to find one that doesn't have at least two lenses at the back. Apple, Samsung, LG and Huawei are just some of the companies equipping its best phones with dual, triple, or even quadruple cameras, giving their owners the kind of creative freedom we could once only get out of a dedicated camera with advanced optics.

But here's the thing: all of these additional cameras are not necessarily better cameras. A monochrome secondary camera is more sensitive to light, but it shoots in black and white only. A wide-angle second cam has a wider field of view, but noticeably distorts images. And those tiny cameras for collecting depth information, well, we're not even sure if they do anything.

Telephoto lens cameras – the kind that Apple popularized with the iPhone 7 Plus – can be useful in many cases, but they aren't perfect either. Here's why.

What's the purpose of a telephoto lens?


Telephoto cameras on smartphones are great at two things. One is that they let you zoom in on your subject without as much degradation in quality as digital zoom would otherwise introduce. We've seen phones with 2x zoom, 3x zoom, and even 5x telephoto zoom in the recently announced Huawei P30 Pro. Secondly, telephoto cameras have a narrower field of view, which makes them ideal for portraits – their optical properties introduce less lens distortion and allow for a narrower, thus less distracting background. 

The 8MP telephoto camera on the Huawei P30 Pro provides a whopping 5x magnification using cleverly designed opitcs

The 8MP telephoto camera on the Huawei P30 Pro provides a whopping 5x magnification using cleverly designed opitcs



Alas, pretty much all smartphone cameras with telephoto lenses are held back by a number of factors. Making matters worse, many of these drawbacks are not immediately obvious to the user.

Telephoto cameras on phones don't do optical zoom


In photography, lenses tend to fall under two general categories: zoom lenses and prime lenses. Zoom lenses have an actual lens element that physically moves to magnify your subject. This is called optical zoom. In contrast, prime lenses are fixed and can't zoom optically. Practically all cameras in modern smartphones, including telephoto ones, use prime lenses since they're smaller and easier to make. Yes, you do get actual zoom with your phone's telephoto camera relatively to its main one, but only at a fixed point.

What this means is that if your phone has a 2x zoom telephoto cam, photos shot at anything between 1x and 1.9x will be zoomed digitally, as if your phone didn't have a telephoto camera at all. Only photos at 2x and beyond will take advantage of the phone's telephoto lens. That's better than nothing, of course, but it's easy for an inexperienced user to wrongly assume that their phone's telephoto hardware is of benefit every single time they zoom in. That's not the case, sadly. 

1.9x zoom? Sorry, that's still done digitally

1.9x zoom? Sorry, that's still done digitally



Telephoto cameras rarely work in low light


In most cases, a bigger camera sensor is a better camera sensor. Its greater surface area lets it absorb more light, and having more light translates into better photos with more detail and less noise. But telephoto cameras on phones tend to use smaller image sensors – ones that pick up less light and are more susceptible to digital noise. They have to in order to achieve the level of magnification their telephoto lens is designed for without the camera module sticking out too much.

Because of this, telephoto cameras rarely work in low-light situations. When the phone's camera software detects that the light in the frame is insufficient, it will not use its telephoto cam for zooming. Instead, it will only do digital zoom with its main camera, and you might not even notice until you later take a closer look at your suspiciously fuzzy-looking photos.

This is a '2x zoom' photo I shot with the Galaxy S10. Since light wasn't enough, the phone zoomed digitally with its main camera instead of using its telephoto one. This is why details look all fuzzy.

This is a '2x zoom' photo I shot with the Galaxy S10. Since light wasn't enough, the phone zoomed digitally with its main camera instead of using its telephoto one. This is why details look all fuzzy.


Telephoto cameras can't focus from up close


I remember how when I got to test the iPhone 7 Plus for the first time, I tried taking some artsy photos of rain droplets on a flower's petals. I did 2x zoom, assuming that the telephoto lens would let me get a much more detailed shot. I was wrong. 

You can't take close-ups like this one with your phone's telephoto lens

You can't take close-ups like this one with your phone's telephoto lens



While a typical smartphone camera can focus on an object as close as 3 inches away from it, the telephoto cameras on all phones I've tested through the years have needed to be at least 1-2 feet away from anything to focus on it. If you're too close and zoom in, your phone will simply do digital zoom with its main camera instead of using its telephoto lens. Again, your phone will give you no indication that you're not zooming with the telephoto lens for the shot.

Nonetheless, a telephoto lens is a valuable asset


The purpose of this brief article is to expose the fundamental flaws in phones' telephoto cameras (and there's more of them) – as I'm sure that knowing what they can and can't do will make you a better photographer. Convincing anyone that there's no point in having a telephoto lens was never my intention. On the contrary, I'm strongly in favor of phones having additional cameras – telephoto, wide-angle, whatever – as it's one of the few realistic ways of improving a phone's photographic potential without ruining its design and appearance. 

Still, I wish that the limitations of these lenses were made clearer to the user – in both the flashy ads we're bombarded by and in the camera apps of our phones. But perhaps that could be just me. Anyway, let me know in the comments below if you learned something new. 

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22 Comments

1. User123456789

Posts: 361; Member since: Feb 22, 2019

52mm is macro, not telephoto. Too many cons: - smaller sensors to keep module same thickness as main camera. - most use f2.4 or f2.6, it is good only for daylight. Should be 2.0 (better night performance and sharpness) Better having for example 30MP to take a 120MP photo, crop the center. Only issues is that would not work for videos.

6. Bankz

Posts: 2477; Member since: Apr 08, 2016

This is the first time I'm actually starting to believe that Phonearena are perhaps getting paid for real. This anti Huawei campaign is becoming embarrassing tbh..

2. charliebigpot

Posts: 2; Member since: Apr 29, 2019

Bookmarking this one for when iPhones will have a telephoto lens and PA will call it revolutionary.

8. Bankz

Posts: 2477; Member since: Apr 08, 2016

The iPhone camera has become the subject of social media mockery since the release of the Huawei p30 pro. Never thought this day would come, Lmao..

3. Ghost04

Posts: 509; Member since: May 03, 2014

iPhones currently has the weakest telephoto feature . Only 2X. While others are offering 3X, 5X even 10X zoom. As iPhone cant compete with others in this feature, it suddenly become a useless feature. The next most important feature in camera will be the one Apple will bring with iPhone 11.

5. oldskool50

Posts: 409; Member since: Mar 29, 2019

Which is precisely why he's trying to make it seem they are not as awesome as we think. Because the telephoto lens on their favorite phone, sucks compared to the competition. How about we all just draw our own conclusions based on the phone we used, and not some biased generalization of the feature, because their favorite phone of choice has a crappy sensor.

7. Bankz

Posts: 2477; Member since: Apr 08, 2016

They are so embarrassing on so many levels now. In fact, they aren't even hiding it anymore ffs..

9. User123456789

Posts: 361; Member since: Feb 22, 2019

Most have 2x. They count as 2x the fact wide is 26mm and secondary 52mm. To be considered 3x, it requires to be triple of main cam. In this situation if main is 26mm, the secondary needs to be 78mm. P20 Pro has bit over 80mm. The "5x" is software trick only. Probably a crop of the final photo. When they count 10x is because the consider from the Ultra Wide. 16 x 10 = 160mm Just need to apply digital zoom for a 120mm to make similar to a 160mm.

4. Macready

Posts: 1797; Member since: Dec 08, 2014

It's not so much the small sensor limiting low light shooting with telephoto lenses (see the improvements made with sub f/1.7 apertures combined with multi frame stacking on the main cameras), it's much more a result of the small physical aperture of the lens used. Which is indeed directly related to the size limitations in phones and physics. Even the "periscope" folding/prism designs (first popularized by Minolta and Sony in their digicams almost 2 decades ago) can't escape this reality, since their aperture is directly limited by the desired thinness of current phones.

10. User123456789

Posts: 361; Member since: Feb 22, 2019

You see the diameter of the aperture, not only the f value. The calculations says the periscope of P30 Pro despite f3.0 or f3.4 has more diameter than iphone with f2.4 and bigger sensor. Lots of things involved when they choose f.

21. HarysViewty

Posts: 57; Member since: Apr 04, 2015

P30pro uses imx520. It's 8mp 1/3.6" sensor, which is an upgrade compared to the previous 1/4". But most 2x zoom are still better, 12mp 1/3.4" with f2.2/2.4/2.6/2.8

23. Macready

Posts: 1797; Member since: Dec 08, 2014

I'm talking about the physical aperture size, not f stops (which are directly related to the true focal length and thus in practice sensor size too).

24. Macready

Posts: 1797; Member since: Dec 08, 2014

But f3.0 is still almost 4 times less light in total than f1.6, for the same sensor size. And sensors in telephoto modules tend to be smaller still, so the actual total light gathering (or difference in physical apertures) is even greater.

11. dumpster666

Posts: 43; Member since: Mar 07, 2019

i guess, the ugly yellow tones from iphones are pretty awesome... right?

12. CristianGMoraru

Posts: 1; Member since: Apr 27, 2019

Yeah ok, this post is useless. Stop kissing apple and being anti Huawei! We get it USA got butthurt cause China is better at making phones and tries to brainwash everyone but that won't change anything. Huawei > Apple. Hell if they add a PEN, Samsung would be in danger.

13. charliebigpot

Posts: 2; Member since: Apr 29, 2019

Telephoto cameras can't focus from up close --> why would you use that lens for close ups when all reviews show that the wide angle lens of the various LG, Samsung and Huawei work much better for close ups?

14. Whitedot

Posts: 694; Member since: Sep 26, 2017

THis made me laugh big time . Of course you have to downplay awesome telephoto lens of course you have to . To a point you are so predictable. I also shouted out loud: : Look! Out there ! A spinless journalism dragon performing it's dance like one of those theatrical muppets. Every day... each muppet a day. Awesome telephoto lens downplay.

18. almostdone

Posts: 421; Member since: Sep 25, 2012

I wonder for human kind sometimes. It's like selling you something they know is bull$hit but they do it anyway even if the product ends up killing you. What's wrong with people these days... Honesty is a good place to start.

16. odachek

Posts: 111; Member since: Sep 01, 2012

Consumers will say, "Who cares?"

19. iloveapps

Posts: 375; Member since: Mar 21, 2019

Yeah most phone camera is just a gimmick. Why not focus on making pictures more natural like iphone. I guess many people are ugly to use beauty cam and other apps to enhance pic.

20. Krjal

Posts: 409; Member since: Dec 19, 2013

I'll still take a telephoto option over a super wide angle every time.

22. japkoslav

Posts: 1341; Member since: Feb 19, 2017

I am really glad I read comments because I did not realize what was the real point of the article.

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