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1.5X Sensors VS. Full Frame and other questions...

 
 
Bryan Olson
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      04-27-2006

Progressiveabsolution wrote:
> What exactly does the 1.5X crop do to the image that is produced from
> the camera?


Exactly that; no more, no less: it capture a smaller part of
the lens' image circle, by a factor of 1.5, both horizontally
and vertically. In terms of area, it captures the center-most
44.4% of what a 35mm full-frame sensor would capture (39%
for a 1.6X crop-factor).

Other effects often attributed to the crop are fictions of
convenience. They are actually caused by other changes made
to compensate for capturing the smaller field of view. For
example, in order to put the same scene in the smaller frame,
we would use a shorter focal length, by the same factor of
1.5. To make a print of the same size from the smaller sensor,
we necessarily apply more enlargement (from capture to print),
by that same factor.

A lens that has a focal length of 50mm on a full-frame
body will still have a focal length of 50mm on a 1.5X-crop
body. The 1.5X-crop body will simply capture a smaller part
of the image formed by the lens.

> In other words, does it degrade the quality of the picture
> when comparing to a full framed camera body?
>
> What is the essential difference in image quality between a full frame
> body and a 1.5-1.6X cropped body?
>
> How much of a difference is there in image quality between the full
> frame body and the 1.5-1.6X sensor bodies?


Those questions are too general to admit an exact answer.
For one thing there are several full-frame bodies and many
1.5-1.6X-crop bodies. Fortunately there are many comparisons
and examples available on-line.

> I'm sure this has been answered but hopefully I can get some more info
> on this.


Yes, and some of the many answers on this issue have even
been correct.


--
--Bryan
 
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John McWilliams
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      04-28-2006
Alfred Molon wrote:
> In article <(E-Mail Removed)>,
> http://www.velocityreviews.com/forums/(E-Mail Removed) says...
>
>>> ...and worse when you need a lot of DOF, for instance for landscape or
>>> architectural shots. To get the same DOF with the full frame lens you
>>> will need to stop down the lens and might have to use a higher ISO
>>> resulting higher noise levels.

>> Yeah, especially when those pesky buildings don't merely sway, but start
>> to dance around. Note: Always shoot mountains at 1600 iso in case they
>> erupt, or jump causing blur at 1/2000.

>
> How funny. There might not be enough light for a handheld shot at F16-
> F22, both outdoors and especially indoors. Stop down the lens and you
> get very quickly exposure times in the range of 1/20s or longer, if it's
> not a bright and sunny day.


Hah! I knew you'd be dour.

Ah, architecture shots in some schools are outdoors, vs. "interior"
shots. Landscapes do tend to the out of doors, world wide. For all three
types just mentioned, I often use a tripod regardless of shutter speed
required.

Or did you merely forget to mention hand held in the post I replied to
prior to this?

--
John McWilliams
 
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MarkČ
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      04-28-2006
Progressiveabsolution wrote:
> What exactly does the 1.5X crop do to the image that is produced from
> the camera? In other words, does it degrade the quality of the
> picture when comparing to a full framed camera body?
>
> What is the essential difference in image quality between a full frame
> body and a 1.5-1.6X cropped body?
>
> How much of a difference is there in image quality between the full
> frame body and the 1.5-1.6X sensor bodies?
>
> I'm sure this has been answered but hopefully I can get some more info
> on this.
>
> Thanks all for your help!


The lens still projects a full-frame image...its just that the sensor only
sees the middle portion of it due to the sensor's size being smaller than
the full-frame projection. Think of it as a slide projector projecting a 6
foot wide image onto a 5 foot wide screen. The projected image stays the
same...you're just not catching all of it on the screen.

Because of this, image quality is not changed at all...rather, you are
simply (in effect), utilizing all your sensor's pixels on the "sweet spot"
of your lens. Some see this as an advantage due to decreased vignetting and
the use of only the sharpest portion of the lens. Others who want wide
angle may not like losing the wide angle of view they are used to...




 
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David J. Littleboy
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      04-28-2006

"MarkČ" <mjmorgan(lowest even number here)@cox..net> wrote:
> Progressiveabsolution wrote:
>> What exactly does the 1.5X crop do to the image that is produced from
>> the camera? In other words, does it degrade the quality of the
>> picture when comparing to a full framed camera body?
>>
>> What is the essential difference in image quality between a full frame
>> body and a 1.5-1.6X cropped body?
>>
>> How much of a difference is there in image quality between the full
>> frame body and the 1.5-1.6X sensor bodies?
>>
>> I'm sure this has been answered but hopefully I can get some more info
>> on this.
>>
>> Thanks all for your help!

>
> The lens still projects a full-frame image...its just that the sensor only
> sees the middle portion of it due to the sensor's size being smaller than
> the full-frame projection. Think of it as a slide projector projecting a
> 6 foot wide image onto a 5 foot wide screen. The projected image stays
> the same...you're just not catching all of it on the screen.
>
> Because of this, image quality is not changed at all...rather, you are
> simply (in effect), utilizing all your sensor's pixels on the "sweet spot"
> of your lens.


Ah, but you are enlarging the sweet spot 1.5x times more. So the question
becomes: is the center section of a 35mm lens really 1.5x times better than
the whole area of a 50mm lens.

Since the 35mm lens is designed to cover 24x36, it's a much wider angle lens
than the 24x36 50mm lens, and is going to have _worse_ performance, not 1.5x
better performance. Even comparing a point, say, 10mm off axis on the 35mm
lens with a point 15mm off axis on the 50mm lens.

> Some see this as an advantage due to decreased vignetting and the use of
> only the sharpest portion of the lens. Others who want wide angle may not
> like losing the wide angle of view they are used to...


The decreased vignetting _wide open_ comes at the cost of reduced
resolution/contrast. It's really hard to make wide angle lenses, and for
lenses with an 80mm or wider FOV, cropped cameras with legacy lenses are a
bad idea.

The good news is that this effect doesn't apply to telephotos. But
telephotos (other than cheap consumer zooms) don't have a sweet spot,
leaving you with the 1.5x greater enlargement penalty. Oops.

The idea that a smaller sensor is better flies against 150 years of
photographic common sense, and is simply nuts.

David J. Littleboy
Tokyo, Japan


 
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Skip M
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Posts: n/a
 
      04-28-2006
"Progressiveabsolution" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> What exactly does the 1.5X crop do to the image that is produced from
> the camera? In other words, does it degrade the quality of the picture
> when comparing to a full framed camera body?
>
> What is the essential difference in image quality between a full frame
> body and a 1.5-1.6X cropped body?
>
> How much of a difference is there in image quality between the full
> frame body and the 1.5-1.6X sensor bodies?
>
> I'm sure this has been answered but hopefully I can get some more info
> on this.
>
> Thanks all for your help!
>

Here's the most graphic example I could find of the difference between a
1.6x crop camera and a full 35mm frame:
http://www.dpreview.com/reviews/canoneos5d/page12.asp

--
Skip Middleton
http://www.shadowcatcherimagery.com


 
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MarkČ
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      04-28-2006
David J. Littleboy wrote:
> "MarkČ" <mjmorgan(lowest even number here)@cox..net> wrote:
>> Progressiveabsolution wrote:
>>> What exactly does the 1.5X crop do to the image that is produced
>>> from the camera? In other words, does it degrade the quality of the
>>> picture when comparing to a full framed camera body?
>>>
>>> What is the essential difference in image quality between a full
>>> frame body and a 1.5-1.6X cropped body?
>>>
>>> How much of a difference is there in image quality between the full
>>> frame body and the 1.5-1.6X sensor bodies?
>>>
>>> I'm sure this has been answered but hopefully I can get some more
>>> info on this.
>>>
>>> Thanks all for your help!

>>
>> The lens still projects a full-frame image...its just that the
>> sensor only sees the middle portion of it due to the sensor's size
>> being smaller than the full-frame projection. Think of it as a
>> slide projector projecting a 6 foot wide image onto a 5 foot wide
>> screen. The projected image stays the same...you're just not
>> catching all of it on the screen. Because of this, image quality is not
>> changed at all...rather, you
>> are simply (in effect), utilizing all your sensor's pixels on the
>> "sweet spot" of your lens.

>
> Ah, but you are enlarging the sweet spot 1.5x times more. So the
> question becomes: is the center section of a 35mm lens really 1.5x
> times better than the whole area of a 50mm lens.


By "image quality," I was referring to the image cast on the sensor. The
degree to which one chooses to enlarge that will determine the extent to
which its flaws become visible...right?

You could also say that you are enlarging any flaw by 1.5x.

> Since the 35mm lens is designed to cover 24x36, it's a much wider
> angle lens than the 24x36 50mm lens, and is going to have _worse_
> performance, not 1.5x better performance.


If I implied otherwise, I didn't mean to.

>Even comparing a point,
> say, 10mm off axis on the 35mm lens with a point 15mm off axis on the
> 50mm lens.
>> Some see this as an advantage due to decreased vignetting and the
>> use of only the sharpest portion of the lens. Others who want wide
>> angle may not like losing the wide angle of view they are used to...

>
> The decreased vignetting _wide open_ comes at the cost of reduced
> resolution/contrast. It's really hard to make wide angle lenses, and
> for lenses with an 80mm or wider FOV, cropped cameras with legacy
> lenses are a bad idea.
>
> The good news is that this effect doesn't apply to telephotos. But
> telephotos (other than cheap consumer zooms) don't have a sweet spot,
> leaving you with the 1.5x greater enlargement penalty. Oops.
>
> The idea that a smaller sensor is better flies against 150 years of
> photographic common sense, and is simply nuts.


Don't interpret my post as proposing any such assertion as to necessitate
your last sentence, there...

I'm very close to lightening my wallet on the 5D...

-MarkČ


 
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David J. Littleboy
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Posts: n/a
 
      04-28-2006

"MarkČ" <mjmorgan(lowest even number here)@cox..net> wrote:
> David J. Littleboy wrote:
>>>
>>> The lens still projects a full-frame image...its just that the
>>> sensor only sees the middle portion of it due to the sensor's size
>>> being smaller than the full-frame projection. Think of it as a
>>> slide projector projecting a 6 foot wide image onto a 5 foot wide
>>> screen. The projected image stays the same...you're just not
>>> catching all of it on the screen. Because of this, image quality is not
>>> changed at all...rather, you
>>> are simply (in effect), utilizing all your sensor's pixels on the
>>> "sweet spot" of your lens.

>>
>> Ah, but you are enlarging the sweet spot 1.5x times more. So the
>> question becomes: is the center section of a 35mm lens really 1.5x
>> times better than the whole area of a 50mm lens.

>
> By "image quality," I was referring to the image cast on the sensor. The
> degree to which one chooses to enlarge that will determine the extent to
> which its flaws become visible...right?


Yes. But I generally assume that one is making the same size prints from
both APS-C and FF. Although I don't consider APS-C adequate for 13x19<g>.

> You could also say that you are enlarging any flaw by 1.5x.


Exactly.

>> Since the 35mm lens is designed to cover 24x36, it's a much wider
>> angle lens than the 24x36 50mm lens, and is going to have _worse_
>> performance, not 1.5x better performance.

>
> If I implied otherwise, I didn't mean to.


I was more arguing with the "sweet spot" theory in general than anything you
said in particular.

>>Even comparing a point,
>> say, 10mm off axis on the 35mm lens with a point 15mm off axis on the
>> 50mm lens.
>>> Some see this as an advantage due to decreased vignetting and the
>>> use of only the sharpest portion of the lens. Others who want wide
>>> angle may not like losing the wide angle of view they are used to...

>>
>> The decreased vignetting _wide open_ comes at the cost of reduced
>> resolution/contrast. It's really hard to make wide angle lenses, and
>> for lenses with an 80mm or wider FOV, cropped cameras with legacy
>> lenses are a bad idea.
>>
>> The good news is that this effect doesn't apply to telephotos. But
>> telephotos (other than cheap consumer zooms) don't have a sweet spot,
>> leaving you with the 1.5x greater enlargement penalty. Oops.
>>
>> The idea that a smaller sensor is better flies against 150 years of
>> photographic common sense, and is simply nuts.

>
> Don't interpret my post as proposing any such assertion as to necessitate
> your last sentence, there...
>


You made the mistake of using the term "sweet spot" without explicitly
criticizing it, which is like waving a red flag in front of a bull...

> I'm very close to lightening my wallet on the 5D...


You'd better hurry. My pet dSLR theory is that the beasts have an 18 month
product cycle, and if one isn't interested in early-adopter pain and
problems, then 6 months after introduction is optimal. If you wait 12
months, then the next great thing will be announced almost immediately.

By the way, don't I still owe you dinner? If you're going to be in the
Boston area June 5 to 11, you could collect. (But aren't you one of the West
Coast crown???)

David J. Littleboy
Tokyo, Japan


 
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MarkČ
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Posts: n/a
 
      04-28-2006
David J. Littleboy wrote:

>> Don't interpret my post as proposing any such assertion as to
>> necessitate your last sentence, there...
>>

>
> You made the mistake of using the term "sweet spot" without explicitly
> criticizing it, which is like waving a red flag in front of a bull...


Ya...I should have known better. Your techno-speak definitely out-shines
anything I have the patience (or math/physics background) to build a
sentence around......

>> I'm very close to lightening my wallet on the 5D...

>
> You'd better hurry. My pet dSLR theory is that the beasts have an 18
> month product cycle, and if one isn't interested in early-adopter
> pain and problems, then 6 months after introduction is optimal. If
> you wait 12 months, then the next great thing will be announced
> almost immediately.
> By the way, don't I still owe you dinner? If you're going to be in the
> Boston area June 5 to 11, you could collect. (But aren't you one of
> the West Coast crown???)


Yes you do, as a matter of fact!
I'll be stuck on the west coast in June...but I'm thinking maybe I should
hold off on collection...and instead wait until I win a few more bets...so I
can COMBINE them into a plane ticket to Japan...where you'll be obligated to
provide the original dinner...and...grand tour of the island.
--I'm thinking that should take in the neighborhood of 50 bets won.
At the rate we bet...I should reach Japan in approximately 50 years.
By that time, we'll both have scant few teeth, and likely little interest in
dinner that requires chewing.
On second thought...I think I'll take that dinner now, thanks!
See ya in Boston!





 
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Alfred Molon
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      04-28-2006
In article <(E-Mail Removed)>,
(E-Mail Removed) says...


> Ah, architecture shots in some schools are outdoors, vs. "interior"
> shots. Landscapes do tend to the out of doors, world wide. For all three
> types just mentioned, I often use a tripod regardless of shutter speed
> required.


Even outdoors there might not be enough light for handheld shots at F16
or F22. Not everybody lugs around a tripod all the time, do you?
--

Alfred Molon
------------------------------
Olympus 50X0, 7070, 8080, E300, E330 and E500 forum at
http://groups.yahoo.com/group/MyOlympus/
Olympus E330 resource - http://myolympus.org/E330/
 
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MarkČ
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      04-28-2006
Alfred Molon wrote:
> In article <(E-Mail Removed)>,
> (E-Mail Removed) says...
>
>
>> Ah, architecture shots in some schools are outdoors, vs. "interior"
>> shots. Landscapes do tend to the out of doors, world wide. For all
>> three types just mentioned, I often use a tripod regardless of
>> shutter speed required.

>
> Even outdoors there might not be enough light for handheld shots at
> F16 or F22. Not everybody lugs around a tripod all the time, do you?


Most folks serious enough to buy full frame DSLRs are serious enough to use
a tripod for landscapes.
If you don't care to use a tripod, there is a very good chance that you
won't be making very good use of full frame resolutions. At that
resolution, you need every bit of lens/steadiness sharpness you can muster.
Otherwise, you may as well not bother...unless the only care is a wide angle
of view.


 
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