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01-02-2014, 01:48 PM   #46
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QuoteOriginally posted by redrockcoulee Quote
As one who shoots medium and large format film cameras I have never seen any mention of f stop equivalents when comparing format equivalents. There are numberous charts comparing field of view and not all are the same due to aspect ratio differences. Those charts will give you the equvalent focal lenghts using 35mm as the standard for 645,66,67,69,4X5,5X7 and 8X10 but have never seen any f stops associated with them.
That's because those old charts weren't concerned about creating equivalent images, they were just telling you the equivalent FOV. Information being left out of charts only proves that info was left out of charts, not that there was no info to include

01-02-2014, 02:27 PM   #47
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QuoteOriginally posted by jsherman999 Quote
That's because those old charts weren't concerned about creating equivalent images, they were just telling you the equivalent FOV. Information being left out of charts only proves that info was left out of charts, not that there was no info to include
But if people were interested in that info it would have been included in at least some of the charts or some of the basic LF instructional book. Of course that info could have been added to the charts as those calculations are not new math
01-02-2014, 08:45 PM   #48
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QuoteOriginally posted by redrockcoulee Quote
But if people were interested in that info it would have been included in at least some of the charts or some of the basic LF instructional book. Of course that info could have been added to the charts as those calculations are not new math
Why would someone compare 135 format and 645 format, they are much further apart than aps-c and 135. It would almost be like comparing your k3 with a 645d and I have yet to see that because they are two different markets. aps-c and 135 share the same market space.
01-02-2014, 08:52 PM   #49
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QuoteOriginally posted by redrockcoulee Quote
personally like both the eyes and the nose to be in focus
This is not a reasonable expectation.

01-03-2014, 09:55 AM - 1 Like   #50
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QuoteOriginally posted by Pete_the_Irish_Guy Quote
Why would someone compare 135 format and 645 format, they are much further apart than aps-c and 135. It would almost be like comparing your k3 with a 645d and I have yet to see that because they are two different markets. aps-c and 135 share the same market space.
Because in the past many people started out in 135 and moved up to MF and LF film. In order to aid them in planning lens acquistion focal length equivalents charts were created. The biggest problem is the different aspects ratios. But no one concerned themselves with f stop equivalents that is so prelavent today.

Owning and shooting cropped and FF digital, comact digital,110,135.6X6,4X5,5X7 and Whole plate plus having shot 645 in the past I am aware of the differences in format.

If one's most used focal length in 135 is 28mm what would you likely be looking for if you went to a 645D system? That is the reason for those chart's existence. For many of the FF crowd there may not be any equivalent if the f-stops did not work out to equal depth of view whereas I would be interested in field of view. That is the point I was trying to make, I am totally aware that MFD and FF digital have different strenghts and different niches.
01-05-2014, 07:52 AM   #51
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QuoteOriginally posted by Class A Quote
While "f/1.8" always achieve the same "exposure" independently from the format, the total amount of light can be vastly different. The reason that an image made with a Q and an f/1.8 lens is noisier than that made with a D800 and an f/1.8 lens is because the D800 sees a much larger amount of total light. The exposure (amount of light per unit square) is identical, but there are a lot more unit squares within the sensor of the D800. That's why it makes sense to calculate the equivalent aperture of the lens on the Q which would be ~f/11. This maximum aperture of f/11 makes it obvious that the Q is not only unable to create images with shallow DOF but also that it collects a lot less light (over 5 stops less).
I am afraid that you were incorrect regarding the light advantage of FF. On FF and APS-C bodies, if you shoot at the same shutter speed and aperture, you need same ISO to achieve same exposure. You do not need higher ISO on APS-C.

FF has "better" noise at high ISO just because they have larger pixels, not because they have larger sensor. Yes FF receive more lights but the lights must be spread into a wider space, so there is no light advantages for just having bigger sensor. Giving same pixel size (i.e. D800 vs D7000, assuming there is no different about sensor technology), the crop and FF will give same result of ISO noise because each pixel receive the same amout of light. Bigger pixel also has advantages in distortion; this means you can shot at extremely small F-stops (i.e. f/16, f/22) with less blurry. Most PnS has very very small pixels, so each pixel receives very less amount of light which produces worse result.

The obvious different between FF and APS is narrower DOF which is not related to pixel size (but sensor size). That's why some review sites use "equivalent aperture in terms of DOF", they never use "equivalent apeture in terms of ISO" or something.

DOF depends on distance from camera to subject, focal length and aperture. To achieve pictures which have same angle of view with FF, on APS-C you have two options:
- Increase the distance, or
- Use shorter lens
Both options will give you wider DOF. As a result, to have the same DOF, with APS-C you need larger aperture (which result in faster shutter speed or lower ISO level to achieve same exposure).

Giving the same lens, same aperture setting, in FF you can shoot at shorter distance which give you narrow DOF, too. That is again the reason of "equivalent aperture in terms of DOF".

Normally, most PnS and smartphones never have narrow DOF because their lenses have very short focal length (the actual value, not the FF-equivalent one).

PS: I did not take circle of confusion into account (bigger sensor = bigger circle = narrower DOF). This also affects DOF only, not light advantage.

Last edited by Reltih; 01-05-2014 at 08:18 AM.
01-05-2014, 11:34 AM   #52
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No

QuoteOriginally posted by Reltih Quote

FF has "better" noise at high ISO just because they have larger pixels, not because they have larger sensor. Yes FF receive more lights but the lights must be spread into a wider space, so there is no light advantages for just having bigger sensor. Giving same pixel size (i.e. D800 vs D7000, assuming there is no different about sensor technology), the crop and FF will give same result of ISO noise because each pixel receive the same amout of light. Bigger pixel also has advantages in distortion; this means you can shot at extremely small F-stops (i.e. f/16, f/22) with less blurry. Most PnS has very very small pixels, so each pixel receives very less amount of light which produces worse result.
The sensor area, not pixel size, is the main determinant here (in combination with a lens supplying the light.) Also the 'big pixels = less distortion' is a new and startling revelation.... (Did you mean to say something about diffraction?)


.

Last edited by jsherman999; 01-05-2014 at 12:15 PM.
01-05-2014, 04:38 PM   #53
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Just wanted to chime in here and contribute one more reason why many users think full frame is better: you use all of the lens that you are paying for.

I once had a friend who shot a Canon 7d with Canon's 24-70/2.8L. I laughed at him because that lens is so heavy and expensive precisely because Canon's engineers worked to make it produce a FF-sized image circle. With the 7d's 1.6 crop factor, he was cropping out the most expensive part of the glass: the corners. Lens engineers work INCREDIBLY hard to get corner sharpness, especially at wide angles like 24mm. So for a Canon user to pay $2K for a lens and then not use the engineering that made it so expensive in the first place is pretty silly. He recently upgraded to a 5d for precisely this reason.

Pentax seems to be the exception in the DSLR world because all of its top lenses were designed for the 1.5 crop factor. Thus Pentax users aren't paying for lens that they're not using. This makes the need for a FF Pentax much less critical. I've never used the DA 15, but compare the size and price to Canon's 14mm and you'll see why it would be pretty stupid to shoot Canon wide angles with a crop factor camera. To use Canon lenses properly, you need a FF DSLR; to use Pentax lenses, you don't.

Unless, of course, you're like me and love looking through a big, beautiful viewfinder and turning a manual focus ring. I've never much liked Pentax digital because I find crop viewfinders so cramped. I may never replace my ME Super with a DSLR, but it would take a Pentax FF to get me to even consider it.

Or, if you're like me and love ultrawides, a FF DSLR makes sense. 20mm, 16mm, 14mm on FF: bring it on. You can't get those FOV equivalents with any Pentax DSLR. Most don't care. I would.


(not possible on Pentax)

01-05-2014, 04:55 PM - 1 Like   #54
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QuoteOriginally posted by Reltih Quote
I am afraid that you were incorrect regarding the light advantage of FF.
No, I wasn't incorrect.

Please read carefully before you claim that I wrote something incorrect.

QuoteOriginally posted by Reltih Quote
On FF and APS-C bodies, if you shoot at the same shutter speed and aperture, you need same ISO to achieve same exposure.
Where did I write anything to the contrary?

Please note that there is a difference between "exposure" (light per unit area) and "total amount of light" (all the light collected by a sensor). If the exposure is the same then a larger sensor will collect more total light.


QuoteOriginally posted by Reltih Quote
FF has "better" noise at high ISO just because they have larger pixels, not because they have larger sensor.
That's incorrect.

Please read this article regarding the irrelevance of pixel size for noise.

QuoteOriginally posted by Reltih Quote
Yes FF receive more lights but the lights must be spread into a wider space, so there is no light advantages for just having bigger sensor.
Almost correct.

There is no (low-) light advantage for a larger sensor if the total amount of light is the same for both sensors (which it will be with equivalent shooting parameters). Note, however, that than the exposure is different.

If the larger sensor actually receives more total amount of light (because for instance it can exploit f-stops on a lens that have no equivalent in the lens for the smaller sensor) then it has a light advantage. If the exposure is the same for both sensors then the bigger sensor will receive crop-factor^2 times more light which directly translates into higher SNR (signal to noise) levels.

QuoteOriginally posted by Reltih Quote
Bigger pixel also has advantages in distortion; this means you can shot at extremely small F-stops (i.e. f/16, f/22) with less blurry.
You seem to be referring to diffraction. However, note that in terms of overall image quality (as opposed to pixel-to-pixel contrast) again the pixel size does not matter. Smaller pixels mean higher resolution which in turn means that you not only capture more details but also better resolve lens limitations (such as aberrations) and diffraction effects. However, that doesn't mean that the bigger pixels capture a better image. Bigger pixels "see" the very same (blurry) image; the fact that they cannot resolve detail at the same level is not an advantage.

QuoteOriginally posted by Reltih Quote
As a result, to have the same DOF, with APS-C you need larger aperture (which result in faster shutter speed or lower ISO level to achieve same exposure).
You need a lower f-ratio if you use a shorter lens. The aperture (i.e., the diameter of the diaphragm in the lens) needs to be exactly the same. Please read the "Equivalence" article by Joseph James.

Another good source on the topic is the "True Reasons for FF" article by Falk Lumo.
01-05-2014, 05:06 PM   #55
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QuoteOriginally posted by jakeblues Quote
I've never used the DA 15, but compare the size and price to Canon's 14mm and you'll see why it would be pretty stupid to shoot Canon wide angles with a crop factor camera.
Please compare the DA 15/4 to the DA 14/2.8 and you'll see that that lens size is not dictated by the size of the image circle but mostly by the lens speed and optical design considerations.

Many Pentax lenses are small because they are relatively slow (the DA 15/4 on APS-C is equivalent to a 23/6 on FF) and make some optical compromises. Having to produce a smaller image circle helps a little bit regarding weight, but not dramatically. In terms of size, the mount diameter defines a lower limit and as I said before the lens speed has a much bigger impact.

QuoteOriginally posted by jakeblues Quote
Or, if you're like me and love ultrawides, a FF DSLR makes sense. 20mm, 16mm, 14mm on FF: bring it on. You can't get those FOV equivalents with any Pentax DSLR.
The Sigma 8-16/4.5-5.6 for APS-C (available for K-mount) includes all the focal lengths you mention. Its FF equivalent is a 12-24/7-8. Pretty slow, but wider than even your 14mm on FF.
01-05-2014, 06:33 PM   #56
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QuoteOriginally posted by jakeblues Quote

(not possible on Pentax)

Huh? I have an 8mm rectilinear lens for my Pentax.
01-06-2014, 04:53 AM   #57
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QuoteOriginally posted by jsherman999 Quote
The sensor area, not pixel size, is the main determinant here (in combination with a lens supplying the light.) .
This seems to be a relatively new concept, but from a common sense perspective, I'm having difficulty understanding it.

A given amount of light enters the lens. That light will do one of the following:

1. land on a pixel, in which case one would think that the larger the pixel, the more light it will receive
OR
2. land on dead space between pixels, in which case it would contribute nothing to the capture process

I don't see where the larger sensor, rather than the larger pixel, is a factor.
01-06-2014, 08:07 AM   #58
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QuoteOriginally posted by bxf Quote
This seems to be a relatively new concept, but from a common sense perspective, I'm having difficulty understanding it.
Thanks for stating that honestly, and you're not alone, a lot of folks are still stuck on the 'larger pixels = better' idea.

QuoteQuote:

A given amount of light enters the lens. That light will do one of the following:

1. land on a pixel, in which case one would think that the larger the pixel, the more light it will receive
OR
2. land on dead space between pixels, in which case it would contribute nothing to the capture process

I don't see where the larger sensor, rather than the larger pixel, is a factor.
Basically: it doesn't matter if the light falls on one big pixel or four smaller pixels in the same area - the same amount of light is being collected per area. To increase the total amount of light captured, you need to increase the area.

You can read this article to see a diagram and how this affects noise in particular.

(Also, keep in mind that 'dead space between pixels' exists on larger-pixel sensors too - they're not just big arrays of completely gapless, large pixels )


.

Last edited by jsherman999; 01-06-2014 at 08:15 AM.
01-06-2014, 08:15 AM   #59
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Just my two cents. Assuming that depth of field is not important to your photo, a change in format is not going to change your ability to get a good exposure.

That said, full frame does give better dynamic range as you go up in iso (at low iso K5 is pretty impressive though), better noise performance in high iso (by one stop), and generally the ability to print/view larger sizes (you can print K5/K3 files 30 inches on a side without pixelization). For a lot of photographers, these specific areas aren't important, but if they are, then full frame definitely has advantages other than narrower depth of field.
01-06-2014, 08:18 AM   #60
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QuoteOriginally posted by jsherman999 Quote
The sensor area, not pixel size, is the main determinant here (in combination with a lens supplying the light.) Also the 'big pixels = less distortion' is a new and startling revelation.... (Did you mean to say something about diffraction?)
Yep, I meant diffraction.

QuoteOriginally posted by Class A Quote
No, I wasn't incorrect.

Please read carefully before you claim that I wrote something incorrect.

Where did I write anything to the contrary?

Please note that there is a difference between "exposure" (light per unit area) and "total amount of light" (all the light collected by a sensor). If the exposure is the same then a larger sensor will collect more total light.
By more total light do you mean on the same picture frame or not? Giving the same lens, FF receives more total light, but the additional light is spread on the additional area around the cropped area. Where is the advantage?
QuoteOriginally posted by Class A;2638729
That's incorrect.

Please read [url=http://www.dxomark.com/Reviews/More-pixels-offset-noise:
this article regarding the irrelevance of pixel size for noise[/url].
Thanks for the link. I will be reading it.

QuoteOriginally posted by Class A Quote
There is no (low-) light advantage for a larger sensor if the total amount of light is the same for both sensors (which it will be with equivalent shooting parameters). Note, however, that than the exposure is different.

If the larger sensor actually receives more total amount of light (because for instance it can exploit f-stops on a lens that have no equivalent in the lens for the smaller sensor) then it has a light advantage. If the exposure is the same for both sensors then the bigger sensor will receive crop-factor^2 times more light which directly translates into higher SNR (signal to noise) levels.
If more signals mean more noise, how do we explain why the Df has very good ISO performance with very big pixels?

QuoteOriginally posted by Class A Quote
You seem to be referring to diffraction. However, note that in terms of overall image quality (as opposed to pixel-to-pixel contrast) again the pixel size does not matter. Smaller pixels mean higher resolution which in turn means that you not only capture more details but also better resolve lens limitations (such as aberrations) and diffraction effects. However, that doesn't mean that the bigger pixels capture a better image. Bigger pixels "see" the very same (blurry) image; the fact that they cannot resolve detail at the same level is not an advantage.
Yes, I meant diffraction. Your argument makes sense.

QuoteOriginally posted by Class A Quote
You need a lower f-ratio if you use a shorter lens. The aperture (i.e., the diameter of the diaphragm in the lens) needs to be exactly the same. Please read the "Equivalence" article by Joseph James.

Another good source on the topic is the "True Reasons for FF" article by Falk Lumo.
Thanks again for the links. It take some time to read them all.

Last edited by Reltih; 01-06-2014 at 08:27 AM.
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