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Archive 2013 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens

  
 
Gonemad
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p.1 #1 · p.1 #1 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


So, in preparation for my birding in the next month or so, I've been doing some math to figure out if there's any significant advantage to pair a 1.6x crop or 1.3x crop DSLR with the 400mm. As it turns out, it is quite significant when the focal length is between 100mm to 200mm, but not significant enough beyond that. The calculation basically converts focal length in mm to the equivalent power in binocular.

mm 1.3x crop 1.6x crop delta
100 38.5 yds 31.3 yds 7.25 yds
200 19.1 yds 15.6 yds 3.5 yds
400 9.6 yds 7.8 yds 1.8 yds
600 6.4 yds 5.2 yds 1.2 yds
800 4.8 yds 3.9 yds 0.9 yds

How to read the results. Using a 100mm lens on a 1.3x DSLR, an object at 100 yds would appear to be 38.5 yds away. Likewise, the same 100mm lens on a 1.6x DSLR would make the object appear at 31.3 yds, which is a significant gain of 7.25 yds difference. But, using a 400mm lens, the difference is only 1.8 yds. That's quite astonishing! Does this even sound reasonable or is my math way off?

EDIT: I removed references to 7D and 1D4, because the specific sensor type was derailing my point which is limited to only the magnification power. Each sensor type will further affect the quality of the image, but that's an exercise and discussion for another time.

Edited on Sep 30, 2013 at 11:45 AM · View previous versions



Sep 29, 2013 at 08:39 PM
JohnBrose
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p.1 #2 · p.1 #2 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


You have to look at pixel pitch or pixel density not sensor size. That's my understanding anyway.


Sep 29, 2013 at 08:59 PM
Pixel Perfect
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p.1 #3 · p.1 #3 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


JohnBrose wrote:
You have to look at pixel pitch or pixel density not sensor size. That's my understanding anyway.


Yes, it has to be part of the calculation, after all a 20D and a 6D, say, have the same reach when FL limited since they have the same pixel density or near enough so. When using binoculars I would always assume you are going to be FL limited anyway.



Sep 29, 2013 at 09:16 PM
Andrew J
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p.1 #4 · p.1 #4 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Way off. If the 7D was full frame it would be over 44MP and the 1DmkIV not even 27MP.


Sep 29, 2013 at 10:28 PM
Gonemad
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p.1 #5 · p.1 #5 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Hmm, I guess the reason I didn't figure pixel density into the equation is because I'm stopping at the image plane (which is the sensor on the DSLR or our pupil if we made an eye piece). In which case, I'm only looking at magnification factor and not the resolving/digitization of the sensor.


Sep 29, 2013 at 10:40 PM
Gonemad
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p.1 #6 · p.1 #6 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Ah, I think the point of confusion is that I actually called for 1D4 and 7D. If I were to look at magnification, I should just point out the 1.3x crop and 1.6x crop factor - leaving the sensor details out of the picture.


Sep 29, 2013 at 10:43 PM
dgdg
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p.1 #7 · p.1 #7 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Way back when, I recall seeing a couple web sights who took this question out in the field. The end result image testing crop vs full frame (usually 7d for the crop) was the crop had modestly better performance if you were significantly focal length challenged. The math gets tricky, at least for me to derive it, trying to factor in everything. Appreciate you running the numbers!


Sep 30, 2013 at 07:40 AM
ggreene
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p.1 #8 · p.1 #8 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Also depends on how high your ISO is. I went from a 1D4 to a 1DX (27MP vs. 18MP) and it definitely makes a difference in good light. My crops for daylight soccer were nicer on my 1D4. Once you get above 1600-2000 ISO the 1DX takes back the advantage because of it's better IQ.

Hoping the 7D2 is the rumored "mini 1DX" as it would be a great companion body to the 1DX for outdoor FL limited situations.



Sep 30, 2013 at 08:49 AM
Scott Stoness
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p.1 #9 · p.1 #9 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


ggreene wrote:
Also depends on how high your ISO is. I went from a 1D4 to a 1DX (27MP vs. 18MP) and it definitely makes a difference in good light. My crops for daylight soccer were nicer on my 1D4. Once you get above 1600-2000 ISO the 1DX takes back the advantage because of it's better IQ.

Hoping the 7D2 is the rumored "mini 1DX" as it would be a great companion body to the 1DX for outdoor FL limited situations.


I suspect that you mean: Once you get above 1600-2000 ISO the 1DX takes back the advantage because of it's better IQ at higher iso's.

I think that 1div would likely do better as long as the light was good.

I get into this issue all the time with my 7d/5diii. 7d on my 600 at f4 vs 5diii on my 600 with 1.4, in theory delivers about the same. 1 stop less on 5diii requires higher iso but the 5diii outperforms the 7d by 1.5 stops. So about tied but 8fps and a bit more magnification have me still using the 7d. And 1.4x on my 600 delivers lots of magnification with better iq than 2x on 5diii.



Sep 30, 2013 at 12:02 PM
jcolwell
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p.1 #10 · p.1 #10 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Gonemad wrote:
Ah, I think the point of confusion is that I actually called for 1D4 and 7D. If I were to look at magnification, I should just point out the 1.3x crop and 1.6x crop factor - leaving the sensor details out of the picture.


There is no "magnification" at the sensor. The image on the sensor is the same size for a 1.6x CF camera as for a full frame camera. The magnification occurs when you enlarge the image to print it or show it on a monitor.












Sep 30, 2013 at 12:10 PM
Gonemad
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p.1 #11 · p.1 #11 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


jcolwell, indeed a picture is worth a thousand words! In some ways, the magnification introduced by the sensor crop factor is what I was referring to. You're right that the image formed on the focal plane is the same for FF and crop cameras. But, as your example illustrates, the alphabet across the crop sensor "appears" larger, or fills more of the sensor area, as compared to FF. That's the type of magnification I was referring to in my calculation.


Sep 30, 2013 at 12:31 PM
mogud
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p.1 #12 · p.1 #12 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


jcolwell wrote:
There is no "magnification" at the sensor. The image on the sensor is the same size for a 1.6x CF camera as for a full frame camera. The magnification occurs when you enlarge the image to print it or show it on a monitor.


When I read the OP's "magnification" statement, I was thinking of a clear explanation of why there is no magnification of anything and then I saw your response. Great explanation jcolwell!



Sep 30, 2013 at 12:36 PM
Ralph Thompson
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p.1 #13 · p.1 #13 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


As I understand it, a pixel is not a pixel. There are different sensors & quality of pixels. As good as a 7D is, the pixel quality is still not of 1D4/X quality. The IQ of the 1D series (of the same generation) is better. I get much better images out of my 1d4 than I do from my 7d.

The quality of the pixel is not related to pixel density. There are some point & shoot cameras out there that cram a huge number of pixels into a sensor. But that does not necessarily give them better IQ.




Sep 30, 2013 at 01:04 PM
Ian.Dobinson
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p.1 #14 · p.1 #14 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Ralph Thompson wrote:
The quality of the pixel is not related to pixel density. There are some point & shoot cameras out there that cram a huge number of pixels into a sensor. But that does not necessarily give them better IQ.



Ralph thats because if you cram more pixels into the same space they have to be smaller and wont gather as much light.
so yes you will get 'better' images from your mk4 over the 7D because you have less pixels over a bigger area .

(and im not saying the 7D is not capable of great images, it is )

thos P&S that cram loads of pixels in a small sensor can produce good images but normally only when conditions are ideal . ie hi ISO's can hurt them bad

There is of course the issue of sensor tech as well .
it would be wrong to say that all large area sensors (FF and 1.3 crop) will always be better than 1.6 crop (and smaller)
I had a mk2n for a while and my 7D could easily trump it at hi ISO's



Sep 30, 2013 at 02:02 PM
skibum5
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p.1 #15 · p.1 #15 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Gonemad wrote:
So, in preparation for my birding in the next month or so, I've been doing some math to figure out if there's any significant advantage to pair a 1.6x crop or 1.3x crop DSLR with the 400mm. As it turns out, it is quite significant when the focal length is between 100mm to 200mm, but not significant enough beyond that. The calculation basically converts focal length in mm to the equivalent power in binocular.

mm 1.3x crop 1.6x crop delta
100 38.5 yds 31.3 yds 7.25 yds
200 19.1 yds 15.6 yds 3.5 yds
400 9.6 yds 7.8 yds 1.8 yds
600 6.4 yds
...Show more

two problems:

1. when you are distance limited the only thing that actually matters (for the most part, actually if you had the same pixel pitch a wider FOV would be nicer since you could get the same reach but have an easier time spotting and tracking; OTOH a smaller FOV would mean less wasted storage space) is pixel density, for the final result it really doesn't matter whether you crop off a little bit of edges or a ton of edges

2. even if you wanted to just go by what you are doing it doesn't make sense to compare the way you are comparing, you need to compare the delta's percentage of the cropped appearance distance difference and you'll notice that the 7.25/31.3 = 1.8/7.8



Sep 30, 2013 at 02:17 PM
skibum5
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p.1 #16 · p.1 #16 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Gonemad wrote:
Hmm, I guess the reason I didn't figure pixel density into the equation is because I'm stopping at the image plane (which is the sensor on the DSLR or our pupil if we made an eye piece). In which case, I'm only looking at magnification factor and not the resolving/digitization of the sensor.


the crop factor isn't magnifying anything on the sensor plane, the lens projects what it projects onto the sensor and whether you mask of a little or a lot of the projection doesn't change the size of anything projected onto it



Sep 30, 2013 at 02:20 PM
skibum5
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p.1 #17 · p.1 #17 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Gonemad wrote:
jcolwell, indeed a picture is worth a thousand words! In some ways, the magnification introduced by the sensor crop factor is what I was referring to. You're right that the image formed on the focal plane is the same for FF and crop cameras. But, as your example illustrates, the alphabet across the crop sensor "appears" larger, or fills more of the sensor area, as compared to FF. That's the type of magnification I was referring to in my calculation.


Although if you were to then break his figures down into pixels and then view the images at 100% you'd see the cropping is completely meaningless when it comes to getting more reach. If you had the same number of photosites per cm^2 on a FF and a 3.0x crop camera and filmed a distant bird from the same spot with the same focal length lens and then viewed both files, both files would produce the exact same detail on the birds (smaller sensors tend to have higher photosite density though so in the case of say a 70D vs a 5D the 70D would have a lot more photosites covering the projected image than the 5D would so it would pick up a lot more detail and give you a lot more effective reach; for a while there the photosite density difference had often been close to the crop factor difference so the real world results had been similar to just using the crop factor)



Sep 30, 2013 at 02:24 PM
Gonemad
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p.1 #18 · p.1 #18 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


skibum5 wrote:
2. even if you wanted to just go by what you are doing it doesn't make sense to compare the way you are comparing, you need to compare the delta's percentage of the cropped appearance distance difference and you'll notice that the 7.25/31.3 = 1.8/7.8


Yes, thanks for pointing out that there's a correlation between the results when normalized on percentage of the delta values. That said, often times we need to look at the absolute values. For example, let's look at an example we're all (hopefully) familiar with: speeding. If someone drove a car at 1 mph and increased by 50% to 1.5 mph has the same percentage of increase if someone started at 60 mph and increased to 90 mph. However, the inherit risk and the severity of impact is different when you look at the absolute values. I guess I took the liberty to provide this exaggerated example, but I just wanted to illustrate that while the math works out (in this case both has 50% speed increase) the risk at each respective absolute speed is radically different.

My point is, I think for the "perceived" magnification I'm proposing, we should only look at the impact of the absolute value.



Sep 30, 2013 at 02:58 PM
Gonemad
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p.1 #19 · p.1 #19 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


skibum5 wrote:
Although if you were to then break his figures down into pixels and then view the images at 100% you'd see the cropping is completely meaningless when it comes to getting more reach. If you had the same number of photosites per cm^2 on a FF and a 3.0x crop camera and filmed a distant bird from the same spot with the same focal length lens and then viewed both files, both files would produce the exact same detail on the birds (smaller sensors tend to have higher photosite density though so in the case of say a 70D vs
...Show more

IF Canon had a FF sensor with enough pixel density that can be cropped to match 7D or 1D4, then all this discussion is moot... In a couple of weeks, I'll do some tests to get real-world results to see if there's any advantage for either using 7D or 1D4 when paired with a super-tele lens (400mm+).



Sep 30, 2013 at 03:19 PM
skibum5
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p.1 #20 · p.1 #20 · No significant advantage to use 1.6x vs 1.3x crop DSLR with super-tele lens


Gonemad wrote:
IF Canon had a FF sensor with enough pixel density that can be cropped to match 7D or 1D4, then all this discussion is moot... In a couple of weeks, I'll do some tests to get real-world results to see if there's any advantage for either using 7D or 1D4 when paired with a super-tele lens (400mm+).



I posted some shots in another thread recently, 7D puts a lot more detail than a 5D2/5D3 when distance limited. In that case I used a 300mm lens but it doesn't really matter what length.




Sep 30, 2013 at 03:22 PM
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