On 2010, June 7 His Steveness has introduced the Apple iPhone 4 which features a new camera module. Two actually but I am going to talk about the main camera (on its rear side) only. And only about its still photography capabilities (it records 720p 30fps HD video as well).
It is typically hard to figure out the exact camera specification for cell phones and to compare them with a P&S camera. E.g., the HTC EVO 4G is said to have an 8 megapixel camera but little else is known. Images shot with the EVO all lack the significant EXIF information!
However, I think I managed to extract the full iPhone 4 camera specs now.
First, the pixels are 1.75 µm (according to Job's keynote) and we may assume that this is the pixel pitch. Sample images are 2592x1936 pixels (5.0 MP, 4.02:3). This makes a 4.54 x 3.39 mm^2 chip (5.67 mm diagonal) which corresponds to a 35mm film camera crop factor of 7.64.
In a P&S, this would be called a 1/3.2" sensor and P&S sensors range between 1/3.8" and 1/1.5" (crop factors between 8.6 and 3.9). So, it is an imaging sensor at the lower end of the P&S range, but it is in the P&S range and with a reasonable number of pixels and a back-illuminated sensor like the Sony Exmor R sensor. Here is a sample image from Apple's web site:
(click on the image for the sample in original size; hosted on apple.com)
Gizmodo.de has published the full EXIF data for exactly this sample photo (it is magically absent from the web sample though ...):
Color space: Uncalibrated
Date and time: 2010/05/07 15:14
Exposure: Auto exposure
Exposure time: 1/887
Flash: Flash did not fire, auto mode
Focal length: 3.85
ISO speed rating: 80
Metering mode: Spot
White balance: Auto
So, the lens is a 3.85 mm f/2.8 lens.
This corresponds to 35mm film camera equivalent lens of 29.4mm f/21.4.
I should note that even an aperture this small is not restricted by diffraction yet (limit at f/2.8 is at 54% of pixel width). This is a good value. But one really shouldn't stop down beyond f/4 and it seems the iPhone 4 has an f/3 fixed aperture lens anyway.
iPhone 4 main camera:
- 5.0 Mpixels (2592 x 1936)
- 1/3.2" back-illuminated CMOS sensor
- 4:3 aspect ratio
- 35 mm film camera crop factor: 7.64
- Low ISO 80 (or better)
- 3.85 mm lens focal length
- f/2.8 lens aperture
- Autofocus: tap to focus
Equivalent 35mm film camera and lens:
- 30 mm f/22
So, don't throw away your FourThird, APS-C or full frame SLR ;)
Besides the deep depth of field, an f/21.4 aperture at ISO 80 produces as much noise as an f/8 lens at ISO 570 (for a given shutter speed). Where 35mm film camera f/8 and APS-C f/5.6 produce the same level of noise.
The iPhone 4 seems to have a camera which should deliver an image quality on par with the lower segment of P&S cameras. It's field of view (no zoom!) corresponds to a 30mm lens (on a 35mm film camera) and it captures as much light (produces as much noise) as a system camera with a lens aperture between f/11 (FourThird) and f/22 (35mm film).
Interesting. Wonder how the Nokia N8 will do. And they are proud of their sensor, so I wonder which sensor it has.ReplyDelete
The Nokia N8 isn't treated as iPhone rival but you're correct, its camera spec looks promising.ReplyDelete
5MP, 8MP or 12MP are irrelevant in this class of camera and 5MP actually are preferred for best image quality. E.g., look at
However, the N8 has a Zeiss 5.4mm f/2.8 lens. And blog article http://blog.gsmarena.com/how-large-is-the-nokia-n8-12-megapixel-large-image-sensor/ does the math and points to a Nokia employee posting in dpreview that the N8 has an 1/1.83" sensor.
However, I challenge this. With 5.4mm focal length and an equivalent focal length which is specified to be 28mm, the crop factor is 5.19 and the imaging sensor type is 1/1.92".
Note that early N8 EXIF seems to report the focal length as 4.6mm only. This would correspond to a crop factor of 6.09 and a 1/2.25" sensor.
The inch quotes use the silly standard convention of 1 inch tube equals a 16mm sensor diagonal ( http://www.dpreview.com/learn/?/Glossary/Camera_System/sensor_sizes_01.htm ).
So, it seems that Nokia is overstating the camera spec a bit but that indeed, its sensor is significantly larger than the iPhone 4 one's.
Using the official 5.4mm spec, the Nokia N8 would have 10.8 Mpixels of iPhone 4's size. Using the EXIF spec, it would be 7.9 Mpixels. Impressive numbers still but we don't know about the sensor's core performance yet (back illumination etc.).
So, the iPhone may still not lead the cell phone camera pack. But it is now close enough to the leaders and I congratulate Apple for not playing the silly Mpixel game. Especially as fewer, larger pixels enable better quality HD video.
The entire industry seems to be repeating the information from that original image, with an aperture of f/2.8.ReplyDelete
The EXIF data from my iPhone4, however reports f/2.4. It's only half a stop, but I thought I'd mention it.
@Zandr, that's interesting. Would make it behave like an f/18 35mm full frame camera. I am still wondering why no vendor quotes relevant camera specs and everybody quotes meaningless megapixels instead.ReplyDelete
This is interesting. And I am so amazed with the improvement! I wonder what the other brands will do after this.ReplyDelete
If I'm not wrong, an aperture of f/2.8 on any crop factor sensor has the same light gathering ability. An f/2.8 is an f/2.8. Yes, from a DOF and background blur point of view it might act as an f/22 on a full frame camera, but the light gathering ability remains the same.
a lens' light gathering ability (for a given field of view) is nothing but it's aperture surface in square mm. Which would be (f/2.8)^2. Insert f and you see that smaller f (because of crop) leads to less light gathering ability.
http://www.luminous-landscape.com/essays/Equivalent-Lenses.shtml cares to explain in some more detail.
The EXIF data from my photos report f/2.4 and a focal length of 4 mm and low ISO 80.ReplyDelete
You may grab data from http://iphone4photos.net where I continue to load photos taken under different conditions.
My iPhone 4 always reports a focal length of 4 mm and F/2.8. I wonder if different iPhone 4 models have different sensors???Delete
3.85mm, 3.9mm and 4mm of course are all the same specifications same within zhe given rounding precision.Delete
i like the all material which you have added in this site its really helpful and good for every one.ReplyDelete
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According to Adobe Lightroom and Flickr the iPhone 4 lens is a 2.85 mm (Flickr rounds to 2.9) f/2.8. Not sure how others are getting f/2.4.ReplyDelete
This was extremely helpful! Didn't want to upgrade my OS just to run the iPhone simulator! The new version of the iPhone SDK requires 10.6.2 and I am on a 10.5.8 box. Thanks again!ReplyDelete
Can I ask a question? I go to a lot of concerts and take photos with my iphone 4 and its totally hit or miss. Mostly, the brightly lit performers show up as totally white or luminescent. I assume this is due to a relatively low shutter speed and no way to alter the aperture.....ReplyDelete
I get somewhat better results with the procamera app in that I can set the white balance and focus manually, but still not good. Sometimes I'll shoot 20 shots as fast as the camera will let me and get one or maybe two decent shots.....almost always with the performers being still and the light being colored instead of bright white.
Any Suggestions? They won't let me take in my wifes Canon t2i......
what you describe is classic for high contrast scenes. You'll have to overexpose for subjects in the dark/shadow and to underexpose for subjects in the bright/sun light/spot lights. So, you need a camera app which allows EV compensation. If you can't find such an app (should exist though), the new HDR function may help too, actually. I can't help you out because I use another camera in similiar situations -- already because of distance to the subject.
Thanks for the information. I really wanna know if iPhone 4 can be compared to some P&S cameras. I would appreciate if someone can put up a small comparison with iPhone 4 camera and some P&S cameras.ReplyDelete
Thank you. I haven't updated to get the HDR function yet (I'm jailbroken). I'll look for another app supporting ev.
So does the iPhone 4 have a wider lense than previous versions?ReplyDelete
The camera does have zoom as a FYI. Not great but significant enough. Biggest advantage to this camera over other iterations is that it has a LED flash which does a great job in low light conditions.ReplyDelete
The camera has no zoom. The flash LED is great indeed. The zoom slider in the camera APP is nothing but a digital crop. The camera itself has no zoom.ReplyDelete
what's the use of back-illuminated sensor of iPhone 4 camera? Is it something to do with dark environment?ReplyDelete
Back-side illuminated CMOS sensors change the silicon layering in order to detect more of the photons hitting the sensor. Sony pioneers its usage in consumer electronics. I don't know if the iPhone 4 uses a Sony sensor (it's likely though). If it does, then here is the explaination of the corresponding Sony Exmor R technology:ReplyDelete
There are a couple of comments here stating that the lens behaves like a "f/22" or "f/18" lens, and even talk of defraction limits in this context. This is totally bogus. An f/2.8 lens is an f/2.8 lens, regardless how big the sensor is behind it, whether you have a phone, camera or elephant attached to it. As far as light-gathering (and defraction) are concerned, it is f/2.8. What DOES "differ" is the depth of field (DOF) when compared to a lens of equivalent focal length (ie, with crop factor applied). The DOF might well be equivalent to f/22 or f/18 on a 35mm camera, but NOT the light gathering or defraction properties. Just wanted that to be clear for everyone :-)ReplyDelete
@other readers: please ignore kaigr's comment.ReplyDelete
@kaigr: I am unfortunate but your knowledge is half-cooked only. There are lens properties and 35mm-equivalent lens properties. And the 35mm-equivalent lens aperture (f-stop) as far as light gathering, diffraction and depth of field are concerned, i.e., as far as any relevant property is concerned, is multiplied by the 35mm crop-factor.
This gives you a first read about the topic: http://www.luminous-landscape.com/essays/Equivalent-Lenses.shtml
Further discussion by private mail only.
About Kaigr comment: 1-The luminance of the image on the image sensor is only dependent on the lens f number, 2- The total light gathering of a camera is the multiplication of the surface of the film by the image luminance. Consequence of 1 and 2: with old film camera, the sensor surface was almost always the same (24x36) and the f-number was sufficient to evaluate the "light gathering" performance of a camera. With digital camera having different sensor format, this assumption is not anymore true and it is necessary to take into account the focal lenght of the camera. EricReplyDelete
Eric, you're right but all the comments complicate a thing which is really stupidly simple:ReplyDelete
A lens gathers light proportional to its (entrance pupil) surface (for a given field of view). That's almost too simple to even talk about. And this is no simplification, I say it as a physicist. And because crop cameras have a small focal length (for a given field of view), their lens diameters are small too even if their f-stop is nominally large.
This is why the 35mm-equivalent f-stop depends on the crop factor and Kaigr was wrong.
How do you calculate the Airy disk size? What wavelength are you using? Cause when I use 550nm (middle of visible spectrum), I get a diffraction limit of 116% of pixel size at f/2.8. For red light (700nm which I think is more relevant because you don't want some but not other wavelengths to blur over the pixels) I get 147%. I think my numbers are more realistic than your 54% from an engineering point of view - take the largest lens the focal length of which fits in your form factor and choose an "off-the-shelf" sensor that exploits the full capabilities of the lens, or slightly beyond that for marketing purposes. Sadly, this is quite a common practice in the camera market....ReplyDelete
Very interesting discussion. Reportedly the iPhone5 will have an 8 megapixel sensor, hopefully overall chip larger by 25%. A 30mm equivalent lens is reasonable as a single focal length choice. Apparently a main reason why the iPhone 5 now will be delayed is because the Sony camera module was to be built in a factory located in, alas, Sendai, right at the prime focus of the recent seismic disasterReplyDelete
@Anonymous: I assume you mistake the Airy disk size for the diffraction limit. The Airy disk radius at f/2.8 and 550nm is 1.88µm or 108% the pixel size. That's about your numbers. But a line *pair* (two pixels) separated by the Airy disk radius is still separated (with a small but non-zero contrast). Therefore, the diffraction-limited resolution is a bit smaller than half the Airy disk radius and is about 50% the pixel size. But never mind, line pairs and pixels are a common source of confusion ;)ReplyDelete
Nice article, but I think your conclusion can be misleading to some readers.ReplyDelete
Although the absolute light gathering ability (and DOF) of the iphone 4 lens is equivalent to between f11 to f22 on a systems camera like you said, f2.8 is still f2.8 on any system in terms of *exposure*. Photographers don't care about absolute light gathering ability, just the relative intensity to make the correct exposure.
If f2.8 @ 1/60s @ ISO 100 gives the correct exposure for a scene on iPhone 4, the same aperture, shutter speed and ISO also gives the correct exposure for any camera system at equivalent field of view.
It is technically correct to say that the iPhone 4's lens "captures as much light (produces as much noise) as a system camera with a lens aperture between f/11 (FourThird) and f/22 (35mm film)" but that is like saying the iPhone 4's retina display which is 3.5" @ 326 pixels per inch (PPI) is equivalent to 163 PPI (7" display) or 38 PPI (30" display).ReplyDelete
Basically a camera lens needs more glass to provide the same f-stop for a bigger sensor just like a bigger monitor needs higher resolution to maintain the same PPI. So it's the amount of light hitting the sensor PER AREA that matters and that's what the f-stop tells you for a particular sensor size. Therefore f/2.8 is f/2.8 no matter what the system is as far as light per area is concerned, unless you plan to use the iPhone lens on a larger sensor somehow...
@Rollin, thanks for your comment but you need to read about lens equivalence more. Don't confuse sensors with displays. You always have to judge things at the system level where a display includes the human eye and a sensor doesn't. Light per area as such has no meaning at the system level.ReplyDelete
General comment: As the general understanding of lens equivalence seems to be poor and this blog article is not meant to discuss it, I'll delete all subsequent attempts to discuss it. Rather send me an email if you have trouble to understand it.
@Falk Lumo, I don't see your email address posted anywhere so I'll just make one last comment. I don't mean to say that you are wrong, it's very informative in fact... i agree about the DOF, diffraction and noise... I've also read the luminous landscape article. Like the comment made before me, the f-stop in terms of exposure (iso/shutter-speed) doesn't change WRT to sensor size. I'm sure you understand this, but I just thought your article might confuse readers to think otherwise (I think it has, judging by the comments)... that's all I'm trying to say.ReplyDelete
Rollin, there is f-stop and equivalent f-stop (like there is focal length/equivalent focal length and ISO/equivalent ISO). Anybody who compares absolute (i.e. non equivalent) numbers between systems of *different* sensor sizes creates the confusion, not me. You either keep ALL numbers absolute, or ALL numbers equivalent. Don't mix'em like you propose. And if the sensor size is an uncommon one, ALWAYS use equivalent numbers as the absolute numbers mean nothing. The exposure would still be correct when using the equivalent triplet. BTW, my email address can be found by following the link to my home page.ReplyDelete
Very interesting post, thank you very much indeed!ReplyDelete
By your logic about equivalence (which would result in 'identical' pictures) the ISO in the example picture with a FF camera would be 5000, since the EV of the scene would be the same (~12 1/3). I do agree with everyone else that you're creating a lot of confusion since very few people talk about equivalent aperture (and ONLY when discussing DOF). The triplet would not be the same as you commented:ReplyDelete
FF exposure (that would result in equivalent DOF and time):
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Just a question. If someone would like to buy a camera which supports 1:1 aspect ratio and has better results from iphone 4 w/ Instagram at night/low light, which one would you recommend? Thank you.ReplyDelete
@zibelum: I would ignore aspect ratio crop and effects like from instagram. These are better added after the shot, like in the dark room in the old days of film.ReplyDelete
Your ticket to night photography are knowing how to do hand-held wireless flash, large lens diameters (normally only available for large sensors), noise reduction software (as in Adobe Lightroom 3 or Topaz), and shake reduction (either optical or sensor shift).
I may be partial, but I don't know about any other camera than the Pentax K-5 which offers similiar low light performance AND stabilizes f/1.4 lenses (30 - 85mm). Just don't use mobile phones or point and shoot at night ;)
I couldn't agree more. Pentax K-5 it is then. Thank you mate!ReplyDelete
However, because of the fact that I'm not looking for something that fancy. I'm into point and shoot at the moment. I need a camera for this job; a camera that I could carry almost everywhere. Less than $500. Any recommendations?ReplyDelete
@zibelum, if it MUST be a P&S, I would look into the Lumix LX5. However, a dSLR like the Pentax K-x has almost top notch low light performance and is under $500 too. And with a 40mm prime, is amazingly small (almost pocketable (with larger pockets) but jumps above $500). A micro-FourThirds like Olympus E-PL1 fits the price target as well but only outperforms the LX5 for chroma noise (not the more important luminance noise). OTOH, if you invest $500 for any interchangeable lens camera and you already pass my blog, be prepared to spend more money for lenses. So, you may want to consider the entire system before taking any decision.ReplyDelete
Isn't it amazing that you can take photos using your iphone and it gives you a very good result. No wonder that people are now excited with the coming iphone 5 which will be out this year.ReplyDelete
I need a camera for this job; a camera that I could carry almost everywhere. Less than $500. Any recommendations? I couldn't agree more. Pentax K-5 it is then. Thank you mate!ReplyDelete
I'm curious if you can do an in-depth break down of the iPhone 4S camera and compare it to the iPhone 4 camera. Very informative analysis that you have provided.ReplyDelete
Like anonymous(not sure how he expects to get a response ) I would be interested in seeing the same analysis for the iPhone 4S camera.ReplyDelete
I see the interest in an analysis of the iPhone 4S camera phone.ReplyDelete
However, according to what I read, the camera has both improved features and worse features:
Better: better sensitivity to light per CMOS area, more pixels, possible better optics.
Worse: smaller sensor (some 15% less surface if I am not mistaken) and a field of view which is less wide (35 rather than 30mm equivalent, possibly due to the smaller sensor).
So overall, it would be a tie and I hesitate to publish a premature blog article. I need to know more. E.g., the improved full well capacity of the new sensor could be a very strong feature allowing to capture much more dynamic range in good light. But this has to be measured actually.
So, I know this much: The iPhone 4S camera is very interesting. f it is better than the iPhone 4 one's, I don't know (yet).
Hi Falk! Excellent post. Do you have the data for the other iOS devices as well, or do you know a table which lists pixel or sensor sizes for all iPhone generations, the iPod Touch and the iPads?ReplyDelete
What i would like to know is how it compares to the short-lived (but still mine after 2 years) Sony Satio with its 12.1MP !!ReplyDelete
I need to know more. E.g., the improved full well capacity of the new sensor could be a very strong feature allowing to capture much more dynamic range in good light. But this has to be measured actually.ReplyDelete
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How large can you print with an iphone 4 photo.It says it only has 72dpi on my images.Does that mean you can enlarge to only 11 by 14 printsReplyDelete
The dpi number in JPGs is completely meaningless, just ignore it. The number of (sharp) pixels is all what matters. For great sharpness (which assumes 240 dpi (240 ppi actually) on the printing side) you can print up to 8" x 11" (roughly A4 paper size). You can print larger, e.g., A2 at 120 dpi which is still sharper than most LCD monitors. But it wouldn't look as sharp anymore if you approached the print too much (which you normally wouldn't do with large prints anyway).Delete
I would say that the iPhone 4's 5 megapixels are enough for about any printing application except maybe a double page magazine feature.
Wich phone is better for taking photos at evening. I m looking for a phone and popular answers:ReplyDelete
1) Iphone 4S
2) Samsung Galaxi 3S
3) Sony Xperia S Nozomi
4) Nokia 808 PureView
I wouldn't normally answer this question w/o a proper lab test. But in this case, it is obvious: the 808 because of its MUCH larger sensor which collects 4x as much light as all the others ...Delete
Stumbled on this page by accident while looking for iphone lens specs. I would like to know whether the iphone lens has a built-in stepper motor and whether it is controllable through software commands. Am looking for leads on using focus-stacking techniques with an iphone for macro photography. ThanksReplyDelete
I am sorry to say that I don't know. Most likely not. I am saying this because what you can do with an iPhone is determined by the iOS API, i.e., all camera apps out there are doing more or less the same thing and for a reason. And AFAIK, stacking is not offered by anybody. Moreover, I am wondering what the max. magnification is like.Delete