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11-03-2014, 01:31 PM   #1
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DSLR "Crop factor misinformation

When camera companies cite the equivalence of a camera with a small sensor as being euivalent to a 35 mm film camera with a longer focal length they are giving the impression that this is a good thing. It is not. You are NOT gaining resolution. You are simply losing field-of-view.
So the 35mm equvalent really refers to the field of view and not the resolution. For example, the K-3 has an "APS-C' sized sensor which is 23.5 x 15.6 mm. The 35mm film camera is 24 x 36 mm. This is a crop factor of 1.5. It is NOT the equivalent of a 1.5x increase in resolution. It is a 1.5x DECREASE in field-of-view. Take this to an extreme. Suppose a camera has a sensor that is 2.4 mm x 3.6 mm. Would this be the same as having a 10X longer focal length ? I don't think so !

Anyway, sorry for the rant. This is a great forum.

11-03-2014, 01:37 PM   #2
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QuoteOriginally posted by wizzster Quote
When camera companies cite the equivalence of a camera with a small sensor as being euivalent to a 35 mm film camera with a longer focal length they are giving the impression that this is a good thing. It is not. You are NOT gaining resolution. You are simply losing field-of-view.
So the 35mm equvalent really refers to the field of view and not the resolution. For example, the K-3 has an "APS-C' sized sensor which is 23.5 x 15.6 mm. The 35mm film camera is 24 x 36 mm. This is a crop factor of 1.5. It is NOT the equivalent of a 1.5x increase in resolution. It is a 1.5x DECREASE in field-of-view. Take this to an extreme. Suppose a camera has a sensor that is 2.4 mm x 3.6 mm. Would this be the same as having a 10X longer focal length ? I don't think so !

Anyway, sorry for the rant. This is a great forum.
Can you give an example of a company "giving the impression that this is a good thing"? I've only seen 35mm "equivalence" stated in factual terms by manufacturers.

QuoteQuote:
It is a 1.5x DECREASE in field-of-view.
Conversely, APS-C is also an increase in "reach" compared with 35mm film.
11-03-2014, 01:55 PM   #3
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Welcome to the forum.

I think I did read something about the field of view bit. I'm curious, though, since I don't have any comparison nor experience with this. Isn't the result pretty much the same? Except for depth-of-field(?) or whatnot, the part that ends up on the sensor would require a much higher focal length if it hit 35mm film instead, no?

And, yes, an even smaller sensor would change the result even more. It's one reason many like the Q system so much since, with adapter, you can cheaply go way beyond 1,000 mm (equivalent). The image quality won't be as good as bigger sensors, of course, even if their resolution were the same.

But it does sound like a nice way to cheat to get closer.
11-03-2014, 02:01 PM   #4
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Here's just 1 eg Canon T3i DSLR
Canon T3i DSLR Camera with 18-55mm Lens 5169B003 - B&H Photo
If you scroll most of the way down, you will see this:

Focal Length 18 - 55mm
Comparable APS-C Focal Length: 28 - 90 mm

Also, what do you mean by "reach" ?

11-03-2014, 02:03 PM   #5
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QuoteOriginally posted by Undot Quote
Welcome to the forum.

I think I did read something about the field of view bit. I'm curious, though, since I don't have any comparison nor experience with this. Isn't the result pretty much the same? Except for depth-of-field(?) or whatnot, the part that ends up on the sensor would require a much higher focal length if it hit 35mm film instead, no?

And, yes, an even smaller sensor would change the result even more. It's one reason many like the Q system so much since, with adapter, you can cheaply go way beyond 1,000 mm (equivalent). The image quality won't be as good as bigger sensors, of course, even if their resolution were the same.

But it does sound like a nice way to cheat to get closer.
No, it's the same as putting a samll mask over the film, to reduce the field.
11-03-2014, 02:04 PM   #6
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Welcome to the forum, you are not alone, crop factor discussions are recurring themes around here quite often.
11-03-2014, 02:09 PM   #7
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A lot of professional photographers use APS-C sensors instead of Full Frame because of the longest focal (1.5 x).
I don't understand why it is supposed that we are "losing" something.
I was using a point and shoot camera and a Samsung Galaxy S4 when I finally got the money for a DSLR, I gained a lot of quality, the possibility to totally customize my shots, to use amazing lenses and to post process RAW files.
I gained in every direction.
I think that the main part of this forum is not shooting Digital Full Frame too, but if someone swaps full frame for APS-C, this just means that they are swapping field of view for longer zoom.
Seriously, this kind of posts which is not starting with correct informations only confuse people.
11-03-2014, 02:09 PM - 2 Likes   #8
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QuoteOriginally posted by wizzster Quote
Focal Length 18 - 55mm Comparable APS-C Focal Length: 28 - 90 mm Also, what do you mean by "reach" ?
Crop factor is a very confusing topic and IMO it's best left alone unless you're an advanced user. Anyway, what this is saying is that a 28-90mm lens on film/FF will give you the same angle of view as a 18-55mm on APS-C digital.

Since APS-C sensors are smaller, they can be better for telephoto applications, just like FF sensors are better for wide-angle applications. Say you have a FF sensor with 16 MP and an APS-C sensor with 16 MP, and you want to shoot something far away using your 300mm lens. The APS-C sensor would actually deliver a higher resolution of the subject within its field of view compared to the larger sensor.

You might want to read this article, which does a good job of explaining how focal lengths affect field of view on different formats:
Table of Equivalent Focal Lengths - Articles and Tips | PentaxForums.com


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11-03-2014, 02:10 PM   #9
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Hey, welcome to the forum! Jumped right in, I see!
Crop factor is only about FoV, but tiny sensors usually still have quite a few MP, so the resolution is higher. This is why the same 200mm lens on a 12MP K-mount DSLR and on a 12MP Q will give different amounts of resolution. This is also an advantage of APSC against FF, since APSC is still big enough for good quality sensor wafers, unlike the smaller sensors that have worse ISO performance, lower bit depth, worse DR, etc. But these differences are becoming smaller and smaller. Micro four thirds cameras these days give great image quality, and new FF cameras have such high MP count that the difference between pixel density is becoming smaller and smaller.
11-03-2014, 02:22 PM   #10
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QuoteOriginally posted by wizzster Quote
When camera companies cite the equivalence of a camera with a small sensor as being euivalent to a 35 mm film camera with a longer focal length they are giving the impression that this is a good thing. It is not. You are NOT gaining resolution. You are simply losing field-of-view.
So the 35mm equvalent really refers to the field of view and not the resolution. For example, the K-3 has an "APS-C' sized sensor which is 23.5 x 15.6 mm. The 35mm film camera is 24 x 36 mm. This is a crop factor of 1.5. It is NOT the equivalent of a 1.5x increase in resolution. It is a 1.5x DECREASE in field-of-view. Take this to an extreme. Suppose a camera has a sensor that is 2.4 mm x 3.6 mm. Would this be the same as having a 10X longer focal length ? I don't think so !

Anyway, sorry for the rant. This is a great forum.
Welcome to the forum.

"Crop" is a dirty word, especially when used correctly.
Example: If you own a "Full-Frame" digital camera, your sensor has been "cropped" smaller than an actual 36x24mm frame.

If you own a APS-C camera, you have a smaller frame than the full-frame camera, but its a different format.
Nobody cropped it. Nobody stole its FoV. Its made to be that way.

The people with the equivalence charts never show you the third, fourth, or fifth columns where their "full-frame" compares to several medium-formats that their "miniature 135 format" was cropped from.
11-03-2014, 02:23 PM   #11
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Welcome to the forum...

QuoteQuote:
You are NOT gaining resolution. You are simply losing field-of-view.
Consider a 24 MP APS_c compared to a 24 MP Full frame. Within the area of the crop sensor, on the FF it's about 11 MP, on the APS-c it's 24 MP. You are gaining a pile of resolution if your subject lies within the cropped area.

Or consider an image where you have a 250mm on crop where 24 MP fills the frame. On a 24 MP FF sensor, you need a 400mm lens to get the same field of view and resolution...

Are you starting to get the hang of it?

Even on a D800 the area of the crop sensor is about the same a K-5. For the area inside the crop sensor you still gain 400/lw/ph using a K-3. So you get more effective magnification based on the smaller pixel size.

In other words, if you're shooting macro.. both with say a Sigma 70 macro, you get way more magnification inside the area of the crop. magnification in the sensor if you shoot both from the same distance. You only maintain resolution equality if you have a 1.5x longer lens on the FF. And that's what the crop factor is about. On two 24 MP cameras. shooting from the same position you'd need a 105 macro, to give you the same FoV as you'd get on the 70 with the APS-c camera.

It's all about what you see through the lens. Try it, you'll see it.
11-03-2014, 02:23 PM   #12
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QuoteOriginally posted by wizzster Quote
Here's just 1 eg Canon T3i DSLR
Canon T3i DSLR Camera with 18-55mm Lens 5169B003 - B&H Photo
If you scroll most of the way down, you will see this:

Focal Length 18 - 55mm
Comparable APS-C Focal Length: 28 - 90 mm

Also, what do you mean by "reach" ?
The description is simply stating the equivalence, it is neither stating nor implying that it is a good thing.

By "reach", I mean the field of view when a lens is used with a so-called crop sensor. For example, a 200mm lens on an APS-C camera will approximate the field of view of a 300mm lens on a 35mm film camera.

Anyway, as others have pointed out, this has been widely discussed in other places on this forum.
11-03-2014, 02:24 PM - 1 Like   #13
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I wouldn't worry too much about crop or no crop, and especially about people's opinions. Does it take great looking pictures? Then go out and shoot
11-03-2014, 02:30 PM   #14
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QuoteOriginally posted by wizzster Quote
No, it's the same as putting a samll mask over the film, to reduce the field.
Maybe I misunderstand the process but isn't that like cropping afterwards? Only using a smaller portion of the film/sensor sensitive area?

QuoteOriginally posted by Na Horuk Quote
Hey, welcome to the forum! Jumped right in, I see!
Ah, it seems any forum or hobby has at least one hot topic like this.

But in some ways this sounds like either a very technical or philosophical question. MP count rises, but pressing them on too small sensors and you still lose image quality (while "gaining" focal range). Technology keeps improving but, of course, at some point physics will get in the way.
Too many variables for me to understand.

But that's what reviews on PF are for...
11-03-2014, 02:33 PM   #15
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QuoteOriginally posted by Adam Quote
You might want to read this article, which does a good job of explaining how focal lengths affect field of view on different formats: Table of Equivalent Focal Lengths - Articles and Tips | PentaxForums.com
Interesting article, this explain everything you need to know
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