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Canon or Nikon: lens-based decision
#31
[quote name='Brightcolours' timestamp='1298026443' post='6213']That is the REAL "in terms of light gathering". A bit bigger than stated, don't you agree (more than 1 stop)?

[/quote]

Lol, it's the best case scenario - Nikon's crop sensor which is only 1.15 stop slower than FF. For instance, Sigma's foveon is 1.5 stop slower and still considered as APS-C. Some f/2.0 lens would act as f/3.5 on such camera <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Smile' />
#32
[quote name='Brightcolours' timestamp='1297982037' post='6200']

A 5D with 35mm lens is the size of a 5 week old kitten, I guess.

[/quote]



Hmmm... the size could be exaggerated, but 5 weeks old kittens weighting approx. 1,5kg... Kittens you mentioned eat cows I suppose...<img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='Big Grin' />
#33
[quote name='PuxaVida' timestamp='1298030995' post='6219']

Hmmm... the size could be exaggerated, but 5 weeks old kittens weighting approx. 1,5kg... Kittens you mentioned eat cows I suppose...<img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='Big Grin' />

[/quote]

Kittens usually are not made from the same materials. A 5D with 35mm f2 weighs under 1kilo btw <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />
#34
[quote name='ThomasD' timestamp='1298028831' post='6217']

Well, I was thinking in terms of EV, where the f-stop is independent of the size of sensor you project the image on. Considering that the light is distributed over a larger area on FF changes the picture of course.

[/quote]

That is not totally correct either (if I understand your sentence correctly). The sensor for each camera spread the light over 1 image each. The FF sensor collects way more light per image. And the hole in the FF lens is a lot bigger, more light passes through with the same f-stop.



You can not look at things in terms of f-values, when you want to understand equivalences. Because, simply, with a smaller sensor light gets cropped off the sides, making the captured light "field of view" more narrow (by crop factor), you have to start looking at the lenses as equivalents by crop factor. And then the f-value changes.



Lets just take a 50mm f2 lens as easy example.

On FF, it has the field of view of 50mm.

It has an f-value of f2.

This means, it has an aperture of: 50/2= 25mm (that is what the f-value really means: focal length / aperture).



On APS-C, a smaller field of view gets captured. The aperture does not change.

Equivalent focal length (field of view) to FF: 50 / 1.5 = 33.33mm

Equivalent f-value to FF: 50mm / 33.33 = f1.5



As you see, with the same light "amount" (same hole size, same field of view captured), the f-value changes.



A hard thing to grasp for many Olympus forums, for some strange reason.



But, you may wonder, how come the exposure times then remain the same? That is because the ISO is messing things up. ISO says NOTHING about sensor sensitivity, it only says that if you use two different sensors, with probably very different sensitivities, the photographer gets roughly the same exposure time with the same f-value and an equivalent focal length. This is done by applying very specific amplification per sensor.



[quote name='ThomasD' timestamp='1298028831' post='6217']

Surely. Looking at all these non-L primes, one may well get to the point where a FF investment becomes cheaper than APS-C. That is, however, also true for Nikon, although Canon has a slightly wider choice of primes.



Any opinions about Canon's 28/1.8, btw? Reviews seem to indicate that one should better avoid that lens.

[/quote]

Measurements of that lens often show it not to be great (like on photozone), but users often praise that lens. There is a (strange?) difference between Nikon and Canon users on forums... Canon users usually are very critical about lenses, where Nikon users tend praise lenses regardless of how good they actually are. This says nothing about the quality of the lenses, just more about a strange culture difference. Since Canon users often praise that lens (28mm f1.8), it might actually be a nice photographic tool. Just know and understand its limits.



For this lens, I think fredmiranda.com is actually very informative:

http://www.fredmiranda.com/reviews/showp...t=2&page=2



And of course pixel peeper:

http://www.pixel-peeper.com/adv/?lens=37...none&res=3
#35
[quote name='Brightcolours' timestamp='1298032922' post='6221']There is a (strange?) difference between Nikon and Canon users on forums... Canon users usually are very critical about lenses, where Nikon users tend praise lenses regardless of how good they actually are. This says nothing about the quality of the lenses, just more about a strange culture difference.[/quote]

That's where certain photozone users kick in, obviously to compensate this culture difference <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='Tongue' />
#36
[quote name='Brightcolours' timestamp='1298031486' post='6220']

Kittens usually are not made from the same materials. A 5D with 35mm f2 weighs under 1kilo btw <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />

[/quote]



Under 1kg?? 35mm f/2 can be 100g only if you get rid of the glasses in it, I suppose... Are you sure?
#37
[quote name='PuxaVida' timestamp='1298035557' post='6223']

Under 1kg?? 35mm f/2 can be 100g only if you get rid of the glasses in it, I suppose... Are you sure?

[/quote]

You are totally correct, I was off by a bit over 100 grams in my recollection of the 5D's weight <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/unsure.gif' class='bbc_emoticon' alt=':unsure:' />
#38
[quote name='Brightcolours' timestamp='1298032922' post='6221']But, you may wonder, how come the exposure times then remain the same? That is because the ISO is messing things up. ISO says NOTHING about sensor sensitivity, it only says that if you use two different sensors, with probably very different sensitivities, the photographer gets roughly the same exposure time with the same f-value and an equivalent focal length. This is done by applying very specific amplification per sensor.[/quote]

Hm. I guess you should have mentioned that ISO is upped only if the pixel pitch is smaller, not because the actual sensor is smaller.



Also I've noticed that you're mixing field of view and focal length - they're not the same. A lens with focal length equal to 50mm and mounted on FF sensor will have horizontal FOV of around 40 degrees. Mounted on ASP-C sensor, the 1.5x crop factor will effectively reduce the horizontal FOV to 27 degrees, which is roughly equivalent to 75mm lens mounted on FF. What I'm trying to say is that FOV is inversely proportional to focal length, therefore you have to multiply by the crop factor, not divide.
#39
[quote name='Lomskij' timestamp='1298054614' post='6230']

Hm. I guess you should have mentioned that ISO is upped only if the pixel pitch is smaller, not because the actual sensor is smaller.



Also I've noticed that you're mixing field of view and focal length - they're not the same. A lens with focal length equal to 50mm and mounted on FF sensor will have horizontal FOV of around 40 degrees. Mounted on ASP-C sensor, the 1.5x crop factor will effectively reduce the horizontal FOV to 27 degrees, which is roughly equivalent to 75mm lens mounted on FF. What I'm trying to say is that FOV is inversely proportional to focal length, therefore you have to multiply by the crop factor, not divide.

[/quote]

Boy, what a confused mess.... Where to start.



ISO is meaningless. That is the main point. Just a 2nd amplification to an unknown amount of amplification.

About pixel pitch... it has NOTHING to do with anything. The whole sensor collects light, the whole sensor makes an image. It is really rather useless to look at 1 pixel at a time.



In case you still want to do that:

If the big and the small sensor have the same amount of sensels, then the bigger sensels will collect more light, the FF ones.

If the sensels of the big one are smaller in a meaningful way (and the pixel pitch is smaller in the same meaningful way), then that means that the pixels in the image will be a lot smaller too, so any noise that would be "gained" per pixel falls away again in similar sized prints.



So, no matter how you look at it, same size pixel or same amount of pixels, the image of the FF sensor (providing we are talking about similar generation tech. for both sensors) will always have about a stop and a bit advantage noise wise (and "ISO WISE").



Of course you have to DIVIDE by the crop factor.



If you use a 50mm lens on FF, and you then want to know an equivalent to 50mm on APS-C (35mm).





I see I made a silly mistake, which I will correct here:

APS-C: 50mm f2. Aperture: 50/2 = 25mm.

FF: 50 / 1.5 = 33.3mm. aperture: 25mm. f-value: 33.3/25= f1.333



There you have it, the corrected numbers. Sorry for erroneously taking 33.33mm for the aperture size.



No where have I confused focal length and field of view. You just might not understand that I meant with (field of view) to indicate that the equivalent focal length is about giving a similar field of view.
#40
[quote name='Brightcolours' timestamp='1298059946' post='6231']

Boy, what a confused mess.... Where to start.



ISO is meaningless. That is the main point. Just a 2nd amplification to an unknown amount of amplification.

About pixel pitch... it has NOTHING to do with anything. The whole sensor collects light, the whole sensor makes an image. It is really rather useless to look at 1 pixel at a time.



In case you still want to do that:

If the big and the small sensor have the same amount of sensels, then the bigger sensels will collect more light, the FF ones.

If the sensels of the big one are smaller in a meaningful way (and the pixel pitch is smaller in the same meaningful way), then that means that the pixels in the image will be a lot smaller too, so any noise that would be "gained" per pixel falls away again in similar sized prints.



So, no matter how you look at it, same size pixel or same amount of pixels, the image of the FF sensor (providing we are talking about similar generation tech. for both sensors) will always have about a stop and a bit advantage noise wise (and "ISO WISE").



Of course you have to DIVIDE by the crop factor.



If you use a 50mm lens on FF, and you then want to know an equivalent to 50mm on APS-C (35mm).





I see I made a silly mistake, which I will correct here:

APS-C: 50mm f2. Aperture: 50/2 = 25mm.

FF: 50 / 1.5 = 33.3mm. aperture: 25mm. f-value: 33.3/25= f1.333



There you have it, the corrected numbers. Sorry for erroneously taking 33.33mm for the aperture size.



No where have I confused focal length and field of view. You just might not understand that I meant with (field of view) to indicate that the equivalent focal length is about giving a similar field of view.

[/quote]

Ok, let me rephrase what I was trying to say. If you have two sensors, the one which will have higher ISO to maintain the same exposure time is the one with smaller pixel pitch, not the one with the smaller sensor size. Basically, yes, you said this in the second post - I've written that just because in the original it sounded like it has to be necessary the APS-C sensor which gets the ISO boosted. I wasn't talking about noise or print size.



Regarding the field of view - yes, my mistake, for some reason I understood that you're talking about FF lens behaviour on a crop sensor, not the matching equivalent for FF.
  
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