What exactly do camera specs mean?

[charpi]

Ok, I've seen things like 1.75micron sized pixels, backlit sensor etc etc for the iPhone 4 camera. But can anyone translate these technical terms into photo quality terms?

From what I have googled so far...

1.75 micron sized pixels will affect the noise in the photo. The iPhone 4 has this and a 5MP camera. The Nokia N8 will have a pixel size of around the same, 1.75 micron, but has a 12MP camera. What does this mean, does it mean that if I take a photo with iPhone 4, and one with a nokia N8, then scale it down to 5MP size, the RAW photos would look very similar? At least in terms of noise levels?

Then I heard about the iPhone's backlit illuminated sensor which "captures" more photons so give less noise, how would that translate to photo quality?

Then the lens size, I *heard* N8 has a 1/1.83" lens and the iPhone 4 has around 1/3.2 lens, what does this mean and how would it affect photo quality? Resolution?

Lastly the focal length. Does it mean cameras with different focal lengths are different in a way that some can take macro shots very well and others normal shots well?

I hope this will not turn into a N8 v iPhone thread, and people who say specs don't matter. I agree with you to a certain extent. But I am just curious to know what is the difference in camera specs and how it translates into differences in photo quality, especially between the N8 and iPhone 4, since both are in the mobile genre. Also, have I missed out any specs which will affect photo quality? (Like aperture size or something?)

So far from what I can see (which has a high chance that I'm wrong) comparing iPhone 4 photos when scaled up to 12MP size with the N8, the N8 wins, but when comparing the N8 photos scaled down to 5MP with the iPhone 4, it is similar, since the pixel size is the same. How wrong/right am I?

Thanks alot for your information and help.

Cheers

 

[charpi]

Anyone? :'(

 

[Fabienne]

Why don't you turn to Google for answers on the camera specs. You can also find some good books on that on Amazon.com. There are some written only on digital photography and probably some about phone cameras, I wouldn't be surprised.

 

[dccorona]

I can't answer all of your questions, but I can answer some

a bigger lens means the camera can capture more light (larger surface area means more rays hit the lens and are captured), meaning a larger picture can be taken. Not larger in the sense that more megapixels is larger, but larger in that more of the scene can be captured

focal length refers to how far behind the lens the light rays converge. Different focal lengths mean the image forms at different locations. The iPhones autofocus lens means it can change focal lengths. When an image appears blurry, this is because the focal length isn't correct for what is being captured.

For example: from a given point on an image, say the top of a persons head, 6 rays of light are captured, each one heading to a different part of the lens. With the proper focal length, all these light rays converge back to a single point BEHIND the lens, If the image sensor is positioned where they converge, than they are captured as a single point. If it is improperly positioned, the points don't line up properly, causing many dim versions of the image to form near each other but not exactly on top of one another, creating the blurriness (6 light rays at one point creates a brighter image than only 1 light ray)

The focal length changing basically allows where the image forms to change, so if an object you are trying to focus on is further away, you change your focal length to cause that objects image to fall directly on the image sensor. This causes objects at further or closer distances to become blurry, because they are not falling directly on the image sensor.

However, I am not sure wether a larger or smaller focal length is better for macro, I just know that your range of possible focal lengths affect how close to an object you can get without having a blurry image.

If you are interested in how an image forms, I can tell you that as well, but it'll probably be another equally long post. Basically the shape of the lens causes light rays to bend inwards, forcing them to eventually converge.

 

[John T]

I suggest you post your question in the Special Interests>Visual Media>Digital Photography section of this Forum. There you should stand a better chance of getting a knowledgeable reply. For example, dccorona did his/her best to answer your query - unfortunately, not entirely correctly. For example, the physical size of a camera lens makes an enormous difference. The diameter of an 'phone camera is only a few mm's, whereas an equivalent lens on even a simple P&S camera can be 10 or more times that size. The advantage of the larger lens is that it can gather more light from the object being photographed enabling pictures to be taken in a wider range of lighting conditions. This is why so many photographs taken on 'phones are often underexposed and grainy.

The other advantage of a large diameter lens is simply in it's construction, with more elements of a higher quality. This results in better quality images free from distortions.

The focal length of a lens widens or narrows the image seen by the camera. A lens with a short focal length is called a wide angle lens because the image covers a wide angle, making it useful for taking shots indoors where space is limited. Conversly, a lens with a long focal length or Telephoto lens will "magnify" the image which makes it useful for photographing objects at relatively long distance from the camera.

A macro lens is simply a lens with a very short focal length. Because the focal length is so short, these lenses can focus on objects very close to the camera, making them ideal for photos of flower heads, insects etc.

Blurry images are the result of incorrect focusing of the image, or camera shake (not holding the camera still whilst taking the photograph) and, within limits, are nothing to do with the focal length.

Hope this helps a bit!

 

[pflau]

1.75 micron sized pixels will affect the noise in the photo. The iPhone 4 has this and a 5MP camera. The Nokia N8 will have a pixel size of around the same, 1.75 micron, but has a 12MP camera. What does this mean, does it mean that if I take a photo with iPhone 4, and one with a nokia N8, then scale it down to 5MP size, the RAW photos would look very similar? At least in terms of noise levels?

The size of the pixel affects the sensitivity - bigger pixel = more sensitive = less noise at a given level of picture brightness.

The number of pixel affects the resolution - more pixel = higher resolution at a given picture size.

Then I heard about the iPhone's backlit illuminated sensor which "captures" more photons so give less noise, how would that translate to photo quality?

It makes the pixels more sensitive and thus give you less noise in dark pictures.

Then the lens size, I *heard* N8 has a 1/1.83" lens and the iPhone 4 has around 1/3.2 lens, what does this mean and how would it affect photo quality? Resolution?

Bigger lens size = more light = less noise or higher shutter speed and thus less blur.

Lastly the focal length. Does it mean cameras with different focal lengths are different in a way that some can take macro shots very well and others normal shots well?

Focal length does not say much about macro shots. It's all in how the lens is built. All lenses take normal shots well, focal length has to do with the angle of view of the picture.

 

[pflau]

The other advantage of a large diameter lens is simply in it's construction, with more elements of a higher quality. This results in better quality images free from distortions.

I would have to disagree. The larger the lens, the more the glass elements are prone to chromatic aberration. Smaller lenses are better - you can have a simpler lens with fewer elements and less distortion. Of course a small lens has a severe disadvantage of being slow.

 

[kfresh]

I can't answer all of your questions, but I can answer some

a bigger lens means the camera can capture more light (larger surface area means more rays hit the lens and are captured), meaning a larger picture can be taken. Not larger in the sense that more megapixels is larger, but larger in that more of the scene can be captured

focal length refers to how far behind the lens the light rays converge. Different focal lengths mean the image forms at different locations. The iPhones autofocus lens means it can change focal lengths. When an image appears blurry, this is because the focal length isn't correct for what is being captured.

For example: from a given point on an image, say the top of a persons head, 6 rays of light are captured, each one heading to a different part of the lens. With the proper focal length, all these light rays converge back to a single point BEHIND the lens, If the image sensor is positioned where they converge, than they are captured as a single point. If it is improperly positioned, the points don't line up properly, causing many dim versions of the image to form near each other but not exactly on top of one another, creating the blurriness (6 light rays at one point creates a brighter image than only 1 light ray)

The focal length changing basically allows where the image forms to change, so if an object you are trying to focus on is further away, you change your focal length to cause that objects image to fall directly on the image sensor. This causes objects at further or closer distances to become blurry, because they are not falling directly on the image sensor.

However, I am not sure wether a larger or smaller focal length is better for macro, I just know that your range of possible focal lengths affect how close to an object you can get without having a blurry image.

If you are interested in how an image forms, I can tell you that as well, but it'll probably be another equally long post. Basically the shape of the lens causes light rays to bend inwards, forcing them to eventually converge.

This pretty much sums it up but I will add a couple of things. It's not just about megapixels. Size and quality of sensor, sensitivity to light and lens are just as important. Without getting too technical, megapixels control how large you photo can be, but sensor and lens control how well that image looks. Images shot from the iPhone are good for the digital world but I wouldn't exactly call them print quality unless shooting in the perfect of circumstances (outdoor with lots of good light). The LED flash isn't very impressive but works in a pinch with very low light. Also, digital zoom sucks, don't use it unless you absolutely have to. It's a marked improvement from past iPhones.

 

[pflau]

digital zoom sucks, don't use it unless you absolutely have to. It's a marked improvement from past iPhones.

It DEPENDS. If you are taking a picture where the picture size is the native resolution of the sensor, which is just about true in all cases, then digital zoom absolutely sucks and you get much better quality blowing up the picture yourself in post processing.

HOWEVER, if you are say shooting a video and the resolution of the video is much smaller than the native resolution of the sensor, then using digital zoom might just make a lot of sense because what the camera does is to just use the subset of the pixels in the center of the sensor - you lose a little sensitivity but you don't lose resolution which is the point.

 

[John T]

The larger the lens, the more the glass elements are prone to chromatic aberration. Smaller lenses are better - you can have a simpler lens with fewer elements and less distortion. Of course a small lens has a severe disadvantage of being slow.

'Fraid not!

I suggest you have a look at the specs (and relative sizes) of quality lenses made, for example, by the likes of Canon and Nikon. Chromatic aberration is just one of the many corrections these lenses have to correct.

 

[pflau]

'Fraid not!

I suggest you have a look at the specs (and relative sizes) of quality lenses made, for example, by the likes of Canon and Nikon. Chromatic aberration is just one of the many corrections these lenses have to correct.

The reason they need to correct them is that those are big lenses!!!

WHY do you think big lenses are so expensive? Because bigger lenses are harder to design and manufacture, all in the name of controlling distortion introduced by the use of larger glasses.