comparison of 24mmF2.8 film/digital

[walterh]

hello,

one of my ( i am probably not the only one) favorite WA - primes is

the 24mmF2.8 lens. i own both the MF (long time) and one AF-D

(brandnew) version. its my impression, that both lenses are nice but

not quite as impressively sharp and contrasty on my D70 as i remember

from film. especially near infinity resolution and contrast seem

inferior in comparison with my 28mmF2.0MF (should be almost as good

as the 28mm at infinity) and about equal to my 20mmF2.8AF lens

(should be definively better than the 20mm), shot in alteration. as

expected near edge falloff is not pronounced on the D70 with the

smaller sensor. i will test this in a few days, as soon as time

permits, but wonder if anybody did a comparison already. existing

experience might "focus" my attention to the right detail :-)

 

cheers and thanks for reading the long question :-)

 

walter

[photojim]

Contrast should be the same, in theory, although, since the digital camera is wasting some of the image circle of this lens that's designed for 35mm, if the light baffling behind the mirror and in front of the shutter is inferior, you might be getting some image flare.

 

As for resolution, because you are enlarging, in effect, the image that your 24mm lens provides (by using a smaller-than-24x36mm sensor), you are losing resolution in a sense. Technically, resolution is the same, but you're enlarging the image more to get a similar-sized print. 75 lpmm of resolution on 35mm means 1800 lines of vertical resolution (on the short dimension) with film and only about 1200 with digital. Furthermore, there is some debate as to whether any modern digital sensor can even resolve 75 lpmm. (I don't shoot digital so I have no answer to this question.)

[peter_h1]

Firstly apologies, I don't have an MF version so I can't do a comparison, this is just my findings on the 24mm after slapping it onto a D70 (yes I've written my name into the 'my first DSLR' book).

 

The 24mm AF-D was probably my favourite lense for my film camera's. After investing in the D70 I was a bit dissapointed at the preliminary shots I'd taken with it though. The loss of focal length due to cropping was not really that much of an issue, however I've found that I'm unhappy with the overall sharpness of the images. At first I wondered if it was that dreaded 'back focus' problem which is doing the rounds, however I'd mostly had the camera set to f/8 or f/11 with targets more then 3 meters away .. so I would doubt back focus would play that much part in it.

 

In general the small size of the CCD coupled with the ability to zoom into 1:1 had me scrutinizing objects for sharpness, even though they were only taking up a very small portion of the image.

 

Also (and I know this sounds weird) but I miss the distortion that would appear on the edges when using it on a film camera. I'd gotten so used to factoring it into my shots and using it as an effect, that the shots I took with the D70 seemed a bit bland to me (regardless of subject of artistic impression).

 

The contrast of the shots also seemed a bit lacking, however I'm sure this is something I could fix up in editing (that said though I'd rather be 'taking' the pictures I want rather then 'making' them).

 

Overall .. from film to digital on the 24mm AF-D has left me a bit dissapointed.

[vivek iyer]

I would second Jim on the sensor resolution.

 

I suspect D70 will be about 60 lp/mm. However, given the fact that the sensor is flat and does not have the same issues as the film (curling, flatness), it is quite reliable. Unless one manages the film perfectly flat and no vibration is allowed to affect the exposure, one need not worry about the lower resolution offered by the digital sensors.

 

I have not checked the 24mm lens but all the high resolution (200 lp/mm and up)lenses I use do alright (ie, better than the "normal" lenses) on D70 but the resolving power of D70 sensor does not come close to Velvia (nothing to do with color saturation and the like, I am only referring to the actual resolving power) and there is absolutely no comparison with my precious Ektars.

[mark_scheuern]

<P><EM><BLOCKQUOTE>

Contrast should be the same, in theory, although, since the digital camera is wasting some of the image circle of this lens that's designed for 35mm, if the light baffling behind the mirror and in front of the shutter is inferior, you might be getting some image flare. </BLOCKQUOTE></EM></P>

<P>I've seen reports that the greater reflectivity of the CCD surface (really the antialiasing filter that covers it) over film can cause increased internal reflections, which seems possible.</P>

[walterh]

thanks for the comments. i am actually not concerned about the "general" comparison film/sensor. i am really interested in how this particular 24mm lens performes on the chip of the D70. (i am absolutely enthusiastic about the performance of other lenses e.g.the 50mmF:1.8 AFD lens on the D70, even if compared to a fine grain film.)

 

i included the (still somewhat subjective) comparizon with the 20mm and the 28mm lenses (both doing about what i expected on the D70, ok, but somewhat less impressive than on film). based on my expectations from comparisons with these wide angle lenses on film and on the D70 i would just expect the 24mm to do somewhat better. that is why i asked for any experience with this specific lens on digital bodies. the performance is not "terrible" but not as excellent as i am used to. as mentioned above already, due to the smaller sensor size compared to film, negative edge effects are not detectable, which is nice of course.

 

cheers

walter

[john_carter_rhodes]

Well I could be wrong, but I don't think there's anything about this lens that would make it perform worse on the D70 than any other lens. As others have said, you should be getting the best from the lens by only using the very central portion of the image circle....as with any other lens designed for 35mm. But you will also be losing the considerably higher resolving power for film over the D70 sensor.

 

That, however, applies to any lens. It's noticeable that Tamron and Canon have begun to produce lenses that specifically cater for the worse flare in digital due to the shiny sensor...but again, this shouldn't mean that your lens has particular problems, unless it is very susceptible to this digital flare.....possible.

 

John.