November 23, 2014, 01:57:55 PM

Author Topic: Major IQ advantage of FF?  (Read 10654 times)

J.R.

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Re: Major IQ advantage of FF?
« Reply #45 on: November 08, 2013, 04:44:14 AM »
A FF camera has a larger area, BUT...
[...]
Has shallower depth of field (NOT always a good thing, ESPECIALLY with long lenses)

This is a misconception. FF does not have shallower DOF. It only has the option for less DOF when needed.

Sure it has shallower depth of field 50mm at f4 on a 7D is roughly equivalent to 30mm f2.5 on a 5D. Same framing, shallower depth of field. When shooting birds in flight, I need usually f8 on a 7D to get the bird at least mostly in focus. On full frame? That's f13. To maintain shutter speed, that means ever rising ISO's.

Yes. The Hi ISO advantage disappears.



And that is just plain BS you are talking. Assuming that you are taking a photograph of a bird with a 400mm lens 50 feet away. Let's see how the DOF works out at f/8 with the 5D3 and the 7D -

7D: Total DOF is 1.41 feet
5D3: Total DOF is 2.23 feet

I think that there are circles of confusion here! It seems pretty obvious that if you have the same lens it gives the same size image on crop and FF sensors, and if the two images are viewed at the same size on a screen or print they will have exactly the same depth of field. If they are not enlarged, but the FF is viewed at a smaller size, it will only appear to have a greater depth of field.

The arithmetic from the DOF calculator proves that the images have the same depth of field when viewed at the same size. The depth of field is calculated from the size of the circle of confusion. For the 5DIII it is 0.03 mm, for the 1.6x crop 7D it is 0.019. And 0.03/0.019 = 1.6. So, when you enlarge the FF image 1.6x to get the same size image as the crop, you exactly compensate for the difference in circles of confusion.

Similarly, look at the ratios of total DOF of the 5D3 to 7D. It equals 2.23/1.41 = 1.6. The image from FF has to be enlarged 1.6x to give the same size print as the crop, and in doing so you multiply the out of focus regions 1.6x and so reduce the depth of field 1.6x.

If talking in terms of equivalence, yes.

I am not sure that he is talking "plain BS". If you obtain the same field of view on the FF as on the 1.6x crop by either standing 1.6x closer with the FF or use a 1.6x longer lens, the crop has 1.6x greater DOF (calculated on the DOF calculator you used). If, as we have agreed, you crop the FF from the same distance with the same lens, 1.6x, then the cropped FF has the same DOF as the crop sensor.

Again, in terms of equivalence, yes. But my point remains that there is a lot of assumption going into the fact that the image has to be cropped by 1.6x.

On second reading I agree that it isn't really "plain BS" as I wrote above. Under the assumption that you would be cropping the FF image to match the APS-C FOV, AprilForever is correct.
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Re: Major IQ advantage of FF?
« Reply #45 on: November 08, 2013, 04:44:14 AM »

Marsu42

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Re: Major IQ advantage of FF?
« Reply #46 on: November 08, 2013, 04:56:57 AM »
Yes. The Hi ISO advantage disappears.

I wouldn't know about you guys with the big lenses, but I know this is true for macro - shooting near 1:1 with a ff has a so much thinner dof that a crop is at least equivalent in terms of required iso, plus the crop has got the longer working distance.

Edit: One more note: High iso on ff is *NOT* equivalent to low iso on crop because the higher iso always has less dynamic range - so the advantage not only disappears, but a disadvantage appears :-o
« Last Edit: November 08, 2013, 05:14:04 AM by Marsu42 »

AlanF

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Re: Major IQ advantage of FF?
« Reply #47 on: November 08, 2013, 05:04:47 AM »
J.R.
Thanks. The discussion got me thinking and I learned something. 
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Zlyden

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Re: Major IQ advantage of FF?
« Reply #48 on: November 08, 2013, 05:53:08 AM »
One more note: High iso on ff is *NOT* equivalent to low iso on crop because the higher iso always has less dynamic range - so the advantage not only disappears, but a disadvantage appears :-o

Great point!

But...

...if instead of "equivalent" we will use more relaxed conceptions like "practical purpose" (that also deals with usability of details, noise, etc. in final image), then a picture shot at ISO 1600 on FF is roughly similar to ones made at ISO 400 on Canon's crops (or FF picture shot at ISO 12800 looks as bad as crop's picture at ISO 3200).

There are lenses like this notorious Sigma 18-35/1.8 that could be considered as an alternate "path to higher IQ" with lower ISO settings for crop camera users. But this lens's size, weight and not-nice reviews about AF precision make it even more difficult decision than "just go and buy 6D body, now you can get for $1600 un-kitted, yes, it does not have touch screen, but features GPS instead" :)
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J.R.

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Re: Major IQ advantage of FF?
« Reply #49 on: November 08, 2013, 06:45:41 AM »
Yes. The Hi ISO advantage disappears.

I wouldn't know about you guys with the big lenses, but I know this is true for macro - shooting near 1:1 with a ff has a so much thinner dof that a crop is at least equivalent in terms of required iso, plus the crop has got the longer working distance.

Edit: One more note: High iso on ff is *NOT* equivalent to low iso on crop because the higher iso always has less dynamic range - so the advantage not only disappears, but a disadvantage appears :-o

I doubt whether it is as easy as it sounds. Diffraction sets in quite early with crop - 60D is rated at f/6.9 as opposed to the FF - f/10.1 - How that may work out in Macro is an animal new to me. 

Most of the macro (to me at least, YMMV) is done using a tripod or some form of support (unless of course you are shooting ants lying down on your belly) so the ISO performance is put into question while doing macro only in specific scenarios.

Note: Regardless of my arguing that FF is better, I'm looking forward to the 7D II because in certain focal length limited scenarios where light is adequate, using the crop will provide better images.
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ajfotofilmagem

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Re: Major IQ advantage of FF?
« Reply #50 on: November 08, 2013, 07:18:24 AM »
I photographed several weddings with Fuji film Provalue ISO 200 on my Canon 300V. Soon after came the Rebel XT, and I tested it grudgingly because the colors of the film Fuji and TTL metering more precise in my Canon 300V give superior results. One thing though encouraged me to abandon the film later: With film (same DOF of full frame) I was forced to use almost all the time F5.6 for groups of people, and digital APS-C I had the same DOF using F3.5. ::) Over time digital cameras were the best , and good films left the market . Today I do not think going back to the DOF with full frame digital, and getting arrested again opening F5.6 for groups of people. For my use , APS-C gives the DOF I need and finally F2.8 lenses are useful. What's the point of having lenses F2.8 and can not use F2.8 because of the extremely shallow DOF? Therefore I say that not everyone will make the leap to full frame someday. I do not intend to do that, and I know I'm not the only one.

candc

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Re: Major IQ advantage of FF?
« Reply #51 on: November 08, 2013, 07:26:40 AM »
this subject gets way over analyzed. if you take a photo with a lens on ff and crop out a square or put it on a crop body, it is the same.
in order to frame a scene the same way with a crop body as ff you either use shorter fl or stand further away, both of which increase dof

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Re: Major IQ advantage of FF?
« Reply #51 on: November 08, 2013, 07:26:40 AM »

ajfotofilmagem

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Re: Major IQ advantage of FF?
« Reply #52 on: November 08, 2013, 07:38:36 AM »
this subject gets way over analyzed. if you take a photo with a lens on ff and crop out a square or put it on a crop body, it is the same.
in order to frame a scene the same way with a crop body as ff you either use shorter fl or stand further away, both of which increase dof
What you say is correct but is not suitable. ::) Reading my comment just above, one realizes that to get deeper DOF on full frame I used F5.6 or F8 to photograph groups of people (at different distances) at wedding parties. According to your suggestion, I could use a 16mm lens on full frame, and accept all geometric distortion of such a lens. :( Or take more away (in a tight room?) to simulate the DOF of APS-C I want. ???

Zlyden

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Re: Major IQ advantage of FF?
« Reply #53 on: November 08, 2013, 08:53:55 AM »
if you take a photo with a lens on ff and crop out a square or put it on a crop body, it is the same.

This was exactly the reason why 6D is the camera I choose to finally replace my 400D with.

If I will not be comfortable with first FF pictures I make, I can just crop 10 megapixels from the center of the images to get what in theory should be the same picture size as that of 400D :)

Of course, it would be better if Canon did such thing for me: just cut 10MP piece from 6D hi-ISO sensor and put it into small APS-C body + magic center AF point that can focus in total darkness. No movies, live-view, touch-screen, wifi-GPS? Perfect -- Oh, thank you very much! This could be an ideal 400D replacement, that I would buy without a second thought for current 6D price tag. (But, better if such camera would be in "kids-toys" class for $300-500. Call it, please, "1200D" or "110D").  :P
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takesome1

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Re: Major IQ advantage of FF?
« Reply #54 on: November 08, 2013, 09:16:46 AM »
A FF camera has a larger area, BUT...
[...]
Has shallower depth of field (NOT always a good thing, ESPECIALLY with long lenses)

This is a misconception. FF does not have shallower DOF. It only has the option for less DOF when needed.

Sure it has shallower depth of field 50mm at f4 on a 7D is roughly equivalent to 30mm f2.5 on a 5D. Same framing, shallower depth of field. When shooting birds in flight, I need usually f8 on a 7D to get the bird at least mostly in focus. On full frame? That's f13. To maintain shutter speed, that means ever rising ISO's.

Yes. The Hi ISO advantage disappears.



And that is just plain BS you are talking. Assuming that you are taking a photograph of a bird with a 400mm lens 50 feet away. Let's see how the DOF works out at f/8 with the 5D3 and the 7D -

7D: Total DOF is 1.41 feet
5D3: Total DOF is 2.23 feet

I think that there are circles of confusion here! It seems pretty obvious that if you have the same lens it gives the same size image on crop and FF sensors, and if the two images are viewed at the same size on a screen or print they will have exactly the same depth of field. If they are not enlarged, but the FF is viewed at a smaller size, it will only appear to have a greater depth of field.

The arithmetic from the DOF calculator proves that the images have the same depth of field when viewed at the same size. The depth of field is calculated from the size of the circle of confusion. For the 5DIII it is 0.03 mm, for the 1.6x crop 7D it is 0.019. And 0.03/0.019 = 1.6. So, when you enlarge the FF image 1.6x to get the same size image as the crop, you exactly compensate for the difference in circles of confusion.

Similarly, look at the ratios of total DOF of the 5D3 to 7D. It equals 2.23/1.41 = 1.6. The image from FF has to be enlarged 1.6x to give the same size print as the crop, and in doing so you multiply the out of focus regions 1.6x and so reduce the depth of field 1.6x.

If talking in terms of equivalence, yes.

I am not sure that he is talking "plain BS". If you obtain the same field of view on the FF as on the 1.6x crop by either standing 1.6x closer with the FF or use a 1.6x longer lens, the crop has 1.6x greater DOF (calculated on the DOF calculator you used). If, as we have agreed, you crop the FF from the same distance with the same lens, 1.6x, then the cropped FF has the same DOF as the crop sensor.

Sure you can crop your picture and get the same DOF. But then you have turned your FF camera in to a crop body. The amount of sensor you use is the same on both. The difference then is that you have a FF body that you are using fewer pixels on the subject.

But who does this? The whole point is silly because who buys a FF camera with the intention of cropping the pictures down to crop body size.


neuroanatomist

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Re: Major IQ advantage of FF?
« Reply #55 on: November 08, 2013, 09:34:44 AM »
if you take a photo with a lens on ff and crop out a square or put it on a crop body, it is the same.

Not quite the same - given that current FF sensors generally have lower pixel density than current APS-C sensors, your cropped FF image will have lower MP than the APS-C image.  For example, a 5DIII image cropped to APS-C framing will have 8.6 MP.  If that lower resolution is sufficient for your output purposes, there's no difference.  But also consider a focal length limited situation in which even the APS-C sensor doesn't provide sufficiently close framing, and you need to crop the APS-C image to 50% of it's original size.  The corresponding crop of the FF image will not have sufficient resolution for 100% display on some current montitors. 

Edit: One more note: High iso on ff is *NOT* equivalent to low iso on crop because the higher iso always has less dynamic range - so the advantage not only disappears, but a disadvantage appears :-o

You seem to be assuming the DR at equal ISO settings is the same on both FF and APS-C, but it's not.  Yes, raising the ISO reduces DR, but the DR of FF is higher to begin with (see below), which mitigates the 'disadvantage that appears'.  For example, at ISO settings above 800, the 5DIII has ~1 stop more DR than the 70D, so when you raise the ISO to compensate for the narrower aperture, you're not incurring a significant reduction in DR (<0.3 EV). 

The upshot is that if you can frame the subject identically, FF has a substantial advantage in terms of IQ.  If you need to crop to APS-C framing because you're focal length limited, there's no significant difference at low ISOs (up to ~800), and at higher ISOs the FF has a progressively bigger advantage, provided the cropped image has sufficient resolution to meet your output needs.
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candc

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Re: Major IQ advantage of FF?
« Reply #56 on: November 08, 2013, 10:18:54 AM »
if you take a photo with a lens on ff and crop out a square or put it on a crop body, it is the same.

Not quite the same - given that current FF sensors generally have lower pixel density than current APS-C sensors, your cropped FF image will have lower MP than the APS-C image.  For example, a 5DIII image cropped to APS-C framing will have 8.6 MP.  If that lower resolution is sufficient for your output purposes, there's no difference.  But also consider a focal length limited situation in which even the APS-C sensor doesn't provide sufficiently close framing, and you need to crop the APS-C image to 50% of it's original size.  The corresponding crop of the FF image will not have sufficient resolution for 100% display on some current montitors. 

Edit: One more note: High iso on ff is *NOT* equivalent to low iso on crop because the higher iso always has less dynamic range - so the advantage not only disappears, but a disadvantage appears :-o

You seem to be assuming the DR at equal ISO settings is the same on both FF and APS-C, but it's not.  Yes, raising the ISO reduces DR, but the DR of FF is higher to begin with (see below), which mitigates the 'disadvantage that appears'.  For example, at ISO settings above 800, the 5DIII has ~1 stop more DR than the 70D, so when you raise the ISO to compensate for the narrower aperture, you're not incurring a significant reduction in DR (<0.3 EV). 

The upshot is that if you can frame the subject identically, FF has a substantial advantage in terms of IQ.  If you need to crop to APS-C framing because you're focal length limited, there's no significant difference at low ISOs (up to ~800), and at higher ISOs the FF has a progressively bigger advantage, provided the cropped image has sufficient resolution to meet your output needs.

What I meant is they are the same in regards to dof. Another thing to remember is with the higher pixel density on the crop bodies you need to use a sharp lens or the sensor out resolves the lens.

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Re: Major IQ advantage of FF?
« Reply #57 on: November 08, 2013, 10:21:07 AM »
I've got both a 7D and a 5DIII.  I like doing wildlife so you would think I grab the 7D over the 5D.  Not so much.

The 5D is much sharper to the point that I can just crop to get the picture I want with the 5D. 

I've played with camera settings, cranking up the sharpening in the 7D helped a little but it struggles compared
to the 5d.  A lot.

That said, if Canon comes out with a 7DII that was "nothing" more than a 5DIII w/ a crop sensor (a good one, one that really gave me the 1.6x tele boost), I'd happily pay $3K for that.  In a heartbeat.  But the current 7D isn't remotely close to as good as the 5DIII in my opinion.

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Re: Major IQ advantage of FF?
« Reply #57 on: November 08, 2013, 10:21:07 AM »

mackguyver

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Re: Major IQ advantage of FF?
« Reply #58 on: November 08, 2013, 10:50:55 AM »
I've got both a 7D and a 5DIII.  I like doing wildlife so you would think I grab the 7D over the 5D.  Not so much.

The 5D is much sharper to the point that I can just crop to get the picture I want with the 5D. 

I've played with camera settings, cranking up the sharpening in the 7D helped a little but it struggles compared
to the 5d.  A lot.

That said, if Canon comes out with a 7DII that was "nothing" more than a 5DIII w/ a crop sensor (a good one, one that really gave me the 1.6x tele boost), I'd happily pay $3K for that.  In a heartbeat.  But the current 7D isn't remotely close to as good as the 5DIII in my opinion.
Same here.  I do lots of wildlife shooting and when I picked up a 5DIII, I thought I'd sell my 5DII and keep my 7D.  After comparing them for several weeks, I realized that the 5DII files were much better than the 7D, even in good light and it was much easier to work with them in post.  I sold the 7D and upgraded my 1.4x II to a 1.4x III and though I still lose some distance, the 5DII and especially 5DIII with the 1.4x or 2x is noticeably better than the 7D files at all ISOs.  The FF bodies have almost no noise from ISO 100-800, while the 7D gets noisy at 400 and only gets worse.

I shot with crops for years, and they are very good, but if you have the money, it's better spent on a FF body, at least as things stand today.

David_in_Seattle

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Re: Major IQ advantage of FF?
« Reply #59 on: November 08, 2013, 11:27:21 AM »

What I meant is they are the same in regards to dof. Another thing to remember is with the higher pixel density on the crop bodies you need to use a sharp lens or the sensor out resolves the lens.

It's not the same in regards to Depth of Field.  At the same focal lengths a full frame sensor will have approximately 1 1/3 stop more depth of field than a crop sensor because of the difference in physical size.

Example:
FF at 50mm vs. Crop (31mm * 1.6 = 49.6mm) - The FF camera will always have the advantage in shallower DOF because the physical size of the sensor is more than twice that of the cropped sensor camera.  The larger sensor size allows for more angles of light to hit the sensor at the same aperture and focal length.  The more angles of light that are able to hit the sensor allows for a shallower depth of field.  I would have added the Depth of Field and Depth of Focus formulas to provide an accurate calculation, but I don't know how to add the special characters...so I recommend searching for it on Google.





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Re: Major IQ advantage of FF?
« Reply #59 on: November 08, 2013, 11:27:21 AM »