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Old Apr 10, 2008, 1:41 PM   #1
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The reason for this comparison is to determine if a F4 lens on a (5D) FF sensor can match a F/2.8 lens on a (40D) 1.6 cropped sensor.

I did this since I could find no direct equivalent to the 17-55mm F/2.8 IS lens in an EF mount. And I wanted to determine what the results would be from using the closest EF mount with IS capabilities. In this test that lens would be the 24-105mm F/4 IS lens mounted on a 5D at my local Best Buy. My 40D had the 17-55mm F/2.8 IS lens.

All shots were done in Av mode. There is no PP done in Bibble other than the cropping to get the center section of the photo.

The "full shot" is the 5D at ISO3200 downsized. If anyone wants the other "full" size shots posted I will do that as well.

Note: All the images were shot in RAW format.

So without further ado here are the pictures that hopefully help anyone else with the same question.

Scene the crops are from:



40d at ISO 800:



40d at ISO 1600:



40d at ISO 3200:



5D at ISO 800:



5D at ISO 1600:



5D at ISO 3200:



The EXIF information is intact on the images so you can see the how the images were shot.

When I compared my XTi (Now gone) to the 40D I currently own I notice the increased ISO handling of noise which I am sure is a result of the Digic III chip and it's 14 bit capabilities. The 5D with the Digic II and "only" 12 bit capabilities sure makes a good showing with it's FF sensor.

Also note the 40D at comparable ISO was shooting at twice the speed of the 5D. You should take into account that variable. So if shutter speed becomes a priority in your equation you would have to ramp up it's ISO setting to match the 40D's ability reduce motion blur. And comparing the 5d at say 1600 versus the 40D at ISO 800 the difference between the images noise gets closer.


I am still trying to make sense of all this. It is all part of my pondering about (possibly) selling my 40D with the 17-55 2.8 and buying the 5D with the 24-105mm F4 lens.

If I were to sell my 70-200mm F/2.8 IS lens and but the 70-200mm F4 IS lens I could put the difference towards the funding of the total package.

Hopefully I presented this "comparison" in a way that makes sense.

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Old Apr 10, 2008, 5:01 PM   #2
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F2.8 gives u a little more speed to capture action. So no matter what camera u useF4 will not give u that shutter speed. It all comes to the question if u want F2.8 or F4 for the kind of ur usage

And 1.6x crop is good in tele en but not so good at the wide angel

FF is vvery good with the 24-105 at 24mm but u need really longer lens to reach at the tele end

Image wise i would say 5D will produce better image over the 40D. The amount of detail the FF sensor can capture can be only experienced. I have had both 40D and 5D and if i were to chose i would pick 5D blind folded
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Old Apr 10, 2008, 6:16 PM   #3
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nymphetamine wrote:
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FF is vvery good with the 24-105 at 24mm but u need really longer lens to reach at the tele end

Image wise i would say 5D will produce better image over the 40D. The amount of detail the FF sensor can capture can be only experienced. I have had both 40D and 5D and if i were to chose i would pick 5D blind folded
As I pointed out (2nd paragraph) in my OP Canon does not make the equivalent of the 17-55mm f2.8 IS in an EF mount. And since I REALLY like IS on my lens that would leave the 24-105mm f4 as the closest match.
And so the reason for my test was too see how the 5d with a f4 lens would handle the 1-stop difference in aperature from a f2.8 lens on my 40d.

Also this test isn't across the whole spectrum of shooting conditions. On a nice bright setting where the need to open up the aperature isn't a requirement I would say "who cares?" I would probably be stopping down for a sharper image.

But at the extreme end of needing light and not having a flash available for use. IE: wedding cermenonies, and wanting these old not-as-steady-as-they-used-to-be hands to have the best lens available on a FF camera I have determined that the higher ISO capability of the 5D will overcome the 1-stop difference between a f2.8 and a f4 lens.

All things being equal you will get no arguement from me. Since my 70-200mm f2.8 IS will mount on a 5d as well as my 40d the only thing I would have to work out is the crop difference.

And that I can work out without shooting both cameras or doing a field test.

Or am I missing something else?
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Old Apr 10, 2008, 6:22 PM   #4
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nymphetamine wrote:
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F2.8 gives u a little more speed to capture action. So no matter what camera u useF4 will not give u that shutter speed. It all comes to the question if u want F2.8 or F4 for the kind of ur usage
If I understand the concept correctly that would assume that the camera(s) used would be bound by the same limitations.

However, considering that the 5D can EASILY outdo the 40D in high ISO performance, not mention wiping up the floor with an XTi why couldn't you compensate for the lack of physical light by ramping up the sensitivity of the sensor?

If you check the EXIF info in the pics I posted and compare then you will see similar noise and detail at the same shutter speed while the ISO and aperature settings are different to compensate for the ability of the lens and the ability of the camera.
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Old Apr 10, 2008, 10:27 PM   #5
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ok my bad i shud have been a bit more detailed on the pros and cons i know of between f2.8 and F4.

Its not jus the shutter speed. At F2.8 the bokeh is going to be a little creamier than @F4

The sharpness at lower ISO is going to be better than the sharpness at higher ISO(Imostly in bigger prints)

The noise difference between 5D and 40D is at worst case one stop. In fact ISO 1000 is almost similar while it gets a little better at ISO 1600 and 3200 for 5D. ISO 3200 on 40D is similar to ISO 3200.

Technically as u said and i stand corrected, the shutter speed can be achieved using the high ISO on the 5D

If ur question is not abt the camera and ust abt the lens(which i misunderstood prior) then i would say the 24-105 will help better along with the 70-200 F4. Since u can achieve the same shutter speed. (only advantage of 70-200 F2.8 IS is that one extra stop u can get at same ISO.) if ur not printing anything bigger than 8*10 i feel using HIGH iso is better.

Personally i prefer using a little lower ISO for marriages since sharpness out of low iso is lot better

5D will be a perfect camera for those low light conditions.

And as i said i stand corrected. I am a novice too. There are experts like Jim, John , NHL and others who can shed more light.

If i had sounded arrogant, i apologise.


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Old Apr 11, 2008, 1:03 AM   #6
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No apologies required. I am new to this thing myself and could have done a better job explaining my points.

I appreciate your reply and questions. The more info I have to work with the (hopefully) better I can get at this.
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Old Apr 11, 2008, 3:40 AM   #7
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Quote:
ok my bad i shud have been a bit more detailed on the pros and cons i know of between f2.8 and F4.

Its not jus the shutter speed. At F2.8 the bokeh is going to be a little creamier than @F4
Well, that's not necessarily right either. Don't forget that with the change in sensor size you lose approximately 1 stop's worth of DOF.

So DOF is equal:
  • 5D, 80mm, f4 [/*]
  • 40D, 50mm, f2.8[/*]
So how nice the bokeh is comes down to how good the lenses are and not specifically the aperture in this comparison. I don't know how good the bokeh is on the 17-55 f2.8, but it's quite nice on the 24-105 on the 5D - in line with what you expect from an L lens.
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Old Apr 11, 2008, 4:27 PM   #8
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Well, that's not necessarily right either. Don't forget that with the change in sensor size you lose approximately 1 stop's worth of DOF.


U r right peripatetic. 5D will def produce a better bokeh but i feel the 5D's bokeh at 24mm F4 will not be as creamy as the 40D 's bokeh at 17mm F2.8. I too hada 5D and i always turn to a F2.8 or F1.2 when it comes to bokeh though 24-105 was my fav lens.

The bokeh from the lens wide open aperture is always pleasing and better than that from the differene in sensor size. But its my personal preference. Scientifically it may be absolutely wrong from my side. But i am just stating my taste.
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Old Apr 11, 2008, 6:33 PM   #9
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Well yes, what you want is both the wide aperture and the larger sensor!

Which is why I mostly use my 50 f1.2


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