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Author Topic: 1DSIII Impressions, Resolution and Lenses  (Read 5473 times)

NikosR

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1DSIII Impressions, Resolution and Lenses
« on: October 19, 2007, 08:15:31 am »

'Having written the above I want to be absolutely clear that resolution on this camera, when the best lenses are used, is extremely high, as is every other aspect of image quality that I have had a chance to evaluate thus far. But in this light it needs to be noted that because of its high resolution the camera is very unforgiving of lens deficiencies.'  (my stress)

I always thought this had to do with pixel density and not resolution (as in number of Megapixels) per se.

This was well identified in the Nikon D2X and now it is, apparently, evident in a Canon camera too. I'm sure this will be the case for the Nikon D300 also.
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Nikos

madmanchan

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« Reply #1 on: October 19, 2007, 09:13:33 am »

Well it has the smallest pixels of any camera with a sensor of this size (i.e., 24 mm x 36 mm). Consequently, edge-to-edge across-the-frame performance of a lens will surely be tested. It is true that the bodies with even smaller pixels, such as the Rebel XTi, may challenge the lens more in the center of the imaging circle, but as we know for most lenses their strong suit is exactly there: in the center of the frame. Similarly, we know that for most lenses their performance falls off as you move away from the center, and this is where we'll likely see differences between the contenders and the champs.
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seberri

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« Reply #2 on: October 22, 2007, 06:09:54 am »

I am also afraid  of a very early diffraction, I hope f/16 will work  like on the 5D
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Ray

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« Reply #3 on: October 22, 2007, 08:07:17 am »

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I am also afraid  of a very early diffraction, I hope f/16 will work  like on the 5D
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The higher the resolving power of the sensor, the earlier the effects of diffraction become apparent, as you stop down. The small sensors of P&S cameras are extremely high resolving and some P&S cameras won't even stop down to f8 where diffraction appears to be pretty obvious.

However, as mentioned before, image resolution at any f stop you care to nominate, will never be worse as a result of higher pixel density. It just might not be better.
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seberri

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« Reply #4 on: October 22, 2007, 09:04:49 am »

the Canon 5D is still good @ f/16, for landscape photography of course
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Giedo

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« Reply #5 on: October 22, 2007, 09:05:21 am »

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Having written the above I want to be absolutely clear that resolution on this camera, when the best lenses are used, is extremely high, as is every other aspect of image quality that I have had a chance to evaluate thus far. But in this light it needs to be noted that because of its high resolution the camera is very unforgiving of lens deficiencies.

Later in the article Michael states that he will take this body to Madagascar with a.o. a 100-400 lens. Michael, why take this best DSLR so far and join it with a lens that is known to show the deficiencies that you speak about? To prove that indeed these deficiencies do show up?  

Seriously, I wonder why you would take the best bodies and economise on lenses. If I were to go on a trip to Madagascar with a 1DsIII, I would match it with 400 or 500 mm fixed focal, especially, since you allready bring a 70-200mm...

Kind regards, Giedo
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Giedo

juicy

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« Reply #6 on: October 22, 2007, 01:44:19 pm »

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Later in the article Michael states that he will take this body to Madagascar with a.o. a 100-400 lens. Michael, why take this best DSLR so far and join it with a lens that is known to show the deficiencies that you speak about? To prove that indeed these deficiencies do show up?  

Seriously, I wonder why you would take the best bodies and economise on lenses. If I were to go on a trip to Madagascar with a 1DsIII, I would match it with 400 or 500 mm fixed focal, especially, since you allready bring a 70-200mm...

Kind regards, Giedo
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Hi!

From Michael's text it is very clear that it's most important to be able to operate with relatively compact and as light camera setup as possible on that trip. Ultimate image quality is secondary concern. Getting the shot is primary. 500mm f/4 weighs more than all of his other lenses combined.

Cheers,
J
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mahleu

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« Reply #7 on: October 22, 2007, 01:53:54 pm »

Just out of curiousity, would a low iso film also reveal lens deficiencies? say Iso 6 or something very slow?
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Ray

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« Reply #8 on: October 22, 2007, 11:33:45 pm »

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Just out of curiousity, would a low iso film also reveal lens deficiencies? say Iso 6 or something very slow?
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Both the lens and the film (or sensor) will reveal the deficiencies of each other. The image resolution (or system resolution) is always a product principally of lens performance (at a given MTF) and sensor/film performance at a given MTF, plus any other variables that might affect resolution.

The basic formula for system resolution involving the two main variables of lens and film performance is 1/S=1/F+1/L where S,F,L are system resolution, film resolution and lens resolution.

So, for example, if we are interested in how fine the image detail will be that has not lost more than 50% of its original contrast, we need the resolution of the lens at 50% MTF and the resolving capability of the film at 50% MTF.

A fine-grained B&W film might be able to record 100 lp/mm with a loss of 50% contrast.  A good lens like the Canon 50/1.4 would probably be capable of resolving only 60 lp/mm with a 50% loss of contrast.

In this case we could say that the film is out-resolving the lens, but that does not mean that the film will therefore be able to faithfully record everything the lens delivers.

If we apply the formula to these figures, we get 1/S=1/100+1/60.

If my maths is correct, S equals just 37.5 lp/mm, significantly less than the separate performances of either film or lens at 50% MTF. Nevertheless, the weak link in this example is the lens. If we were to double the resolution of the lens at 50% MTF we would get a bigger increase in system resolution than we would if we were to double the resolution that the film can record at 50% MTF, whilst keeping lens resolution the same.

For example, if 1/S=1/100+1/120, then S=54.5 lp/mm.

If 1/S=1/200+1/60, then S=46 lp/mm. That's still an improvement, however. Despite the fact that the lens is the weak link, we have still increased image resolution by improving the resolving power of the film. (I don't think it would be possible to produce a lens that could deliver 120 lp/mm at 50% MTF.)
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mahleu

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« Reply #9 on: October 23, 2007, 04:28:04 am »

Thankyou for that explanation. Very helpful.
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