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Author Topic: APS-C lens mm are correct  (Read 22443 times)

Hillsilly

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Re: APS-C lens mm are correct
« Reply #30 on: December 04, 2012, 11:11:50 PM »
Results: I was wrong. The Canon film Rebel was wider at 35mm with the EF lens than the 7D was at 35mm with the EF-S lens. How embarrassing. At least I learned something.

Darn - Was just about to pipe in with a possible explanation.  The 7D has 100% viewfinder coverage and magnification.  A lot of cheaper film cameras had less - generally around 90% with only 70% magnification.  This might have explained why they might have been perceived as similar.

But on thinking about it further, the 7D magnification would be based on the cropped image size, not a 35mm image size.  Maybe they wouldn't be similar at all.  I can understand why people find it confusing.
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Re: APS-C lens mm are correct
« Reply #30 on: December 04, 2012, 11:11:50 PM »

insanitybeard

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Re: APS-C lens mm are correct
« Reply #31 on: December 05, 2012, 05:22:58 AM »
Not my intent, sorry...the 10-22mm is a great lens, IMO.  Do note that I called out distortion specifically, that's notoriously difficult to control in a FF ultrawide lens, and much easier to control with the smaller elements used in an EF-S lens.

The EF-S 17-55mm, 15-85mm, and 10-22mm lenses all deliver optical performance that is on par with many L-series lenses, and in fact, those lenses all outperform 'sort of equivalent' L-series lenses when comparing both on the same APS-C camera (e.g. the 17-55mm is better than the 16-35L II and 24-105L when comparing all of them on a 7D - and I know this from both test charts and personal experience).  But when you put a different camera into the equation, and compare an EF-S lens on APS-C to an L-series lens on a recent FF/APS-H body, the larger sensor confers some IQ advantages.   So, for example, the 16-35L II on a 5DII will deliver better overall performance (although barrel distortion is definitely worse) than the equivalent framing of the 10-22 on a 7D (again, from both charts and my own real-world experience having used both combos).  The IQ of the 10-22mm in the 7D is already very good, it's just that the 16-35 + FF is slightly better.

You can see an aspect of that in the real world (sort of) with people who've popped off the rubber piece on the 10-22's lens mount and used it on a 1DIV - the 10-22 delivers images on the APS-H that are better than those from an APS-C body.

This interests me- does the FF sensor (or APS-H for that matter)- without getting too technical- deliver better IQ due to its larger area and greater light gathering ability (and presumably larger pixels) or does it also have something to do with the FF sensor utilising more of the surface area of the optics in the lens- hence APS-C sensors being more demanding on lenses because they focus the light through a smaller area of glass?
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Re: APS-C lens mm are correct
« Reply #32 on: December 05, 2012, 06:55:18 AM »
This interests me- does the FF sensor (or APS-H for that matter)- without getting too technical- deliver better IQ due to its larger area and greater light gathering ability (and presumably larger pixels) or does it also have something to do with the FF sensor utilising more of the surface area of the optics in the lens- hence APS-C sensors being more demanding on lenses because they focus the light through a smaller area of glass?

The light gathering ability of the larger sensor helps especially with low light but the larger enlarging ratios associated with displaying pictures of the same size (screen or prints) is also a factor.  For lenses of the same generation and made from the same manufacturing technology, FF will win automatically because of its larger area (resolution based on line pairs/length).  APS-C will require sharper lenses to compete with FF to offset FF's larger area and smaller enlarging ratio.

neuroanatomist

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Re: APS-C lens mm are correct
« Reply #33 on: December 05, 2012, 08:17:09 AM »
This interests me- does the FF sensor (or APS-H for that matter)- without getting too technical- deliver better IQ due to its larger area and greater light gathering ability (and presumably larger pixels) or does it also have something to do with the FF sensor utilising more of the surface area of the optics in the lens- hence APS-C sensors being more demanding on lenses because they focus the light through a smaller area of glass?

Mostly the former, And mostly due to the larger total area of the sensor, which gathers more total light.  Actually, performance at the edges of the image circle is worse on all lenses.   There is no differential advantage when comparing an EF lens on full frame to an EF-S lens on APS-C, but an APS-C sensor uses 'sweet spot' of an EF lens.
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insanitybeard

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Re: APS-C lens mm are correct
« Reply #34 on: December 05, 2012, 08:50:22 AM »
Mostly the former, And mostly due to the larger total area of the sensor, which gathers more total light.  Actually, performance at the edges of the image circle is worse on all lenses.   There is no differential advantage when comparing an EF lens on full frame to an EF-S lens on APS-C, but an APS-C sensor uses 'sweet spot' of an EF lens.

I may have explained the point I was trying to make badly.... I know corner performance will always be worse towards the edge of the image circle and that using EF lenses on crop uses the centre portion of the image circle hence the sweet spot effect, what I was trying to say was:

 Is ultimate performance and resolution of APS-C going to be more limited than FF because the light is focused/concentrated through a smaller area of glass in the lens on APS-C than FF- ie, APS-C will start to show up limitations of the optics themselves before FF? (disregarding issues such as CA and drop in resolution away from the centre of the image circle which may be more pronounced on FF due to the larger image circle)

Even now I don't think I've explained myself well enough. Put another way, I guess I am trying to say that the optical glass has it's limitations and that if you are trying to focus light through a smaller area of that glass (as in APS-C) those limitations will become evident sooner?
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Sporgon

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Re: APS-C lens mm are correct
« Reply #35 on: December 05, 2012, 09:02:53 AM »
This interests me- does the FF sensor (or APS-H for that matter)- without getting too technical- deliver better IQ due to its larger area and greater light gathering ability (and presumably larger pixels) or does it also have something to do with the FF sensor utilising more of the surface area of the optics in the lens- hence APS-C sensors being more demanding on lenses because they focus the light through a smaller area of glass?

The light gathering ability of the larger sensor helps especially with low light but the larger enlarging ratios associated with displaying pictures of the same size (screen or prints) is also a factor.  For lenses of the same generation and made from the same manufacturing technology, FF will win automatically because of its larger area (resolution based on line pairs/length).  APS-C will require sharper lenses to compete with FF to offset FF's larger area and smaller enlarging ratio.
If I am reading this correctly you are saying FF is better because it is larger than APS, therefor has less enlarging to reach a given size like 35mm against 6X7 ?

That's not the case, pixels are pixels. An 18MP FF image has just the same "enlargement" as a 18MP APS-C or DX or whatever. The advantage ( at least in theory) is that in the FF the pixels are larger and therefor should be able to record better information. However this advantage is being eroded with new technology. ( I know there are many other advantages, but "size" wise MP is MP.)
« Last Edit: December 05, 2012, 09:06:41 AM by Sporgon »

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Re: APS-C lens mm are correct
« Reply #36 on: December 05, 2012, 09:17:12 AM »
The new direction of this thread started with the comparison of the 10-22 to the 16-35 and the performance of a crop sensor wide.

The thing to keep in mind, for landscape and things wide the best performance is going to come out of the primes. The TSE 17's and 24 and the 24mm f/1.4L. Since there are no Canon primes made to mimic these primes range for a crop sensor, the FF will always be in the lead on the wide end if for no other reason (despite sensor quailty) being available glass.

It seems this thread is moving toward the high density 7D sensor vs the low density 5D II or III sensor debate.
« Last Edit: December 05, 2012, 09:19:13 AM by PackLight »

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Re: APS-C lens mm are correct
« Reply #36 on: December 05, 2012, 09:17:12 AM »

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Re: APS-C lens mm are correct
« Reply #37 on: December 05, 2012, 09:27:49 AM »
If I am reading this correctly you are saying FF is better because it is larger than APS, therefor has less enlarging to reach a given size like 35mm against 6X7 ?

That's not the case, pixels are pixels. An 18MP FF image has just the same "enlargement" as a 18MP APS-C or DX or whatever. The advantage ( at least in theory) is that in the FF the pixels are larger and therefor should be able to record better information. However this advantage is being eroded with new technology. ( I know there are many other advantages, but "size" wise MP is MP.)

So, if you have a 18 MP iphone camera (assuming it existed), that will give you the same enlargement ratio as a 18MP APS-C?  The enlargement ratio is based on final print size/sensor size.  To cope with the higher enlargement ratio, the smaller sensor needs to have a higher resolution/precision lens to compensate for the smaller sensor.

kubelik

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Re: APS-C lens mm are correct
« Reply #38 on: December 05, 2012, 09:30:04 AM »
tristan, it's possible that you had an amazing and lifelike dream where APS-C focal length indicators became not only true but also equivalent focal lengths.  I know I've had dreams where exceptionally awesome (but unfortunately unrealistic) things would happen, and I woke up really believing in them. 

it would be great to have all the APS-C standard zooms start at 18mm equivalent, rather than the current 29mm equivalent.  let's be honest, 29mm is only wide angle if you're a portrait shooter.  to a generalist, which most APS-C owners are, lenses should really be at least 25mm equivalent (16mm or wider focal length).  a 16-120 would be the same zoom ratio as an 18-135, and way, way more useful.

neuroanatomist

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Re: APS-C lens mm are correct
« Reply #39 on: December 05, 2012, 09:33:20 AM »
Is ultimate performance and resolution of APS-C going to be more limited than FF because the light is focused/concentrated through a smaller area of glass in the lens on APS-C than FF- ie, APS-C will start to show up limitations of the optics themselves before FF? (disregarding issues such as CA and drop in resolution away from the centre of the image circle which may be more pronounced on FF due to the larger image circle)

No - what you're describing is purely an effect of pixel density, independent of sensor size (although it's generally true that comparing sensors of a similar generation, the APS-C sensor will have a higher pixel density).  From a resolution standpoint, a larger sensor will deliver higher resolution (in terms of line width/picture height) simply because the height of the picture is greater.

It seems this thread is moving toward the high density 7D sensor vs the low density 5D II or III sensor debate.

Agreed - let's not go there.   :-X
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insanitybeard

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Re: APS-C lens mm are correct
« Reply #40 on: December 05, 2012, 09:44:56 AM »
Thanks all for the input.... Apologies for hijacking!
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wjm

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Re: APS-C lens mm are correct
« Reply #41 on: December 05, 2012, 10:34:32 AM »

But why doesn't Canon print on the lens itself 29-216mm? The 18-135mm printing is misleading then.

Like rj79in said: it is a 18-135 lens. A reason why people use the 1.6 factor is that they want to compare different lenses (the "field of view" mentioned before).

For example: I'm going on a city trip and I want to make some 'general' photo's. I probably want to bring and standard zoom. But what is a standard zoom? If I own a FF camera it is somthing like a 24-105, on a crop 15-85 and on a 4/3 something like a 14-50. I own a 5DII and use the range 24-28mm of my 24-105 a quite often in these situations. A also own a 40D as backup. When I would bring a 18-50 it would be no good (it starts at '28mm' compared to my 5DII with 24-105). I won't get the same "field of view".

With compact cameras the problem is even worse. The Canon S100 has a 5.2-26.0mm lens, the Canon A1300 has a 5.0-20mm lens. Which one is best for wide angle photography (IQ excluded)? One whould say: 5.0mm is wider then 5.2mm but sensor size is different in both cameras. Therefore you need the crop factor. These are about 4.6 for the S100 and 5.8 for the A1300, this gives a eqv. 24-120 and a 28-140 lens. So the S100 is 'wider'.

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Re: APS-C lens mm are correct
« Reply #42 on: December 05, 2012, 11:44:17 AM »
I am amazed by the community here

questions like these with such a insistent and confident tone which is doomed to be false would initiate a series of "flaming" in other forum.

yet participants of this thread took great lengths to correct the thread-starter again and again politely even though he was not convinced with his mistake

kudos to everyone here
« Last Edit: December 07, 2012, 10:54:48 AM by Renzokuken »

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Re: APS-C lens mm are correct
« Reply #42 on: December 05, 2012, 11:44:17 AM »

Sporgon

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Re: APS-C lens mm are correct
« Reply #43 on: December 05, 2012, 12:12:26 PM »
If I am reading this correctly you are saying FF is better because it is larger than APS, therefor has less enlarging to reach a given size like 35mm against 6X7 ?

That's not the case, pixels are pixels. An 18MP FF image has just the same "enlargement" as a 18MP APS-C or DX or whatever. The advantage ( at least in theory) is that in the FF the pixels are larger and therefor should be able to record better information. However this advantage is being eroded with new technology. ( I know there are many other advantages, but "size" wise MP is MP.)

So, if you have a 18 MP iphone camera (assuming it existed), that will give you the same enlargement ratio as a 18MP APS-C?  The enlargement ratio is based on final print size/sensor size.  To cope with the higher enlargement ratio, the smaller sensor needs to have a higher resolution/precision lens to compensate for the smaller sensor.

The final print size is related to the sensor "size", but in terms of enlargement, a sensor's size is defined by its digital information - mega pixels bits of information, not by its physical dimensions, as film would be. So yes, an 18MP iphone sensor would give an image the same size as an APS-C or FF or MF when viewed at 100%, that is when your computer program is adding in an equal amount of information in the viewed image. So in terms of enlargement of the displayed image, a 5D mk1 has to be "enlarged" more than a 7D despite the fact that the 7D's sensor is physically smaller.

However, you are quite right about the inability of a lens to resolve onto so many tiny pixels. Unclear information recorded by the very small chip will also result in your computer program not being able to add to the information clearly, resulting in a much poorer "enlargement".  Larger sensors have many many advantages over much smaller ones, but physical enlargement is not one of them - because they are not physically enlarged.

I know this is getting a little of topic, but it is surprising how many people think FF is better because it isn't enlarged as much as a smaller sensor ! Likewise many people don't realise that your computer is adding to the information. And I'm not sticking up for APS because I really dislike the "crop factor" effect for the sort of photography I do.

Chuck Alaimo

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Re: APS-C lens mm are correct
« Reply #44 on: December 05, 2012, 12:36:21 PM »
well damn, i was all ready to make some witty replies to the OP, but, you all beat me to the punch, and the OP beat me to his own punch too....lol

Wow though, gotta love how topics turn though!  Quite the surprise of info!  Go forum go!
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Re: APS-C lens mm are correct
« Reply #44 on: December 05, 2012, 12:36:21 PM »