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01-19-2009, 08:32 AM   #1
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Is this lens faulty ? Or is it my expectations ?

I have just purchased a K20D with the 16-45mm & an FA 1.4 50mm. I'm unhappy with the IQ of the 16-45, and since this is my first DSLR & I'm a novice I could do with some help from you kind folks in identifying whether I need to send the lens for service. I read the reviews of the lens & the review in Dpreview & was expecting sharp images. I can't get a sharp image to save my life. I've adjusted the exposure bias using charts downloaded from this site - and it was a bit front focused - I adjusted it with a compensation of -2. Here's some images:

First the image that set me wondering whether the lens was faulty - its from a PS Canon A620 at f4:

Next a shot with the FA at f4

And then the 16-45 at f4 & f8

I can't get the quality of the 16-45 to match even the Canon shot - which is at a much lower resolution. The Lens seems soft overall tho F8 IS a bit better.

Do I need to send it back ? Or am I expecting too much ?

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01-19-2009, 08:59 AM   #2
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first, your canon shot at F4 is not even close to being equivalent to an SLR being shot at F4. i dont want to bother doing the math but i think if you were to shoot with your slr you would need to set it to F32 or something to compare to F4 on a point and shoot (there is a formula online if you want 100% accuracy)

second, how are you shooting your SLR, are you using RAW or JPEG. If shooting RAW, how are you processing your pictures. If shooting jpeg, what quality of jpeg are shooting at, and how did you set the in-camera jpeg processing?

third, which mode are you shooting in, and what is the ISO?

fourth, are you using a tripod?

fifth, in the future, try not to strip exif info (or use an uploaded that doesnt strip it), can you post up the shutter speeds of all the shots?

thank you.
01-19-2009, 09:33 AM   #3
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I'm sorry to have to break the news to you, but the only real answer your going to get here is shoot in RAW and PP. Pentax's JPEG's aren't up to par with Canon or Nikon.
01-19-2009, 09:52 AM   #4
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QuoteOriginally posted by Gooshin Quote
first, your canon shot at F4 is not even close to being equivalent to an SLR being shot at F4. i dont want to bother doing the math but i think if you were to shoot with your slr you would need to set it to F32 or something to compare to F4 on a point and shoot (there is a formula online if you want 100% accuracy)

second, how are you shooting your SLR, are you using RAW or JPEG. If shooting RAW, how are you processing your pictures. If shooting jpeg, what quality of jpeg are shooting at, and how did you set the in-camera jpeg processing?

third, which mode are you shooting in, and what is the ISO?

fourth, are you using a tripod?

fifth, in the future, try not to strip exif info (or use an uploaded that doesnt strip it), can you post up the shutter speeds of all the shots?

thank you.
Thanks for the reply
The shots were taken in raw on the Pentax & resized in Photoshop.

The 50mm FA shot was 1/640 ISO 200 F4. The 16-45 shots were
45mm 1/60 F4 ISO 100 & 45mm 1/125 ISO 800 F8.

The info about the comparison between PS & SLR apertures was helpful, thanks.

01-19-2009, 10:08 AM   #5
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QuoteOriginally posted by lostkj233 Quote
I'm sorry to have to break the news to you, but the only real answer your going to get here is shoot in RAW and PP. Pentax's JPEG's aren't up to par with Canon or Nikon.
DO you mean the on-camera Jpeg ? I shoot in Raw & then use the Pentax utilities to create the Jpegs - are the Pentax utilities also poor performers ?
01-19-2009, 10:09 AM   #6
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QuoteOriginally posted by holdgaj Quote
Thanks for the reply
The shots were taken in raw on the Pentax & resized in Photoshop.

The 50mm FA shot was 1/640 ISO 200 F4. The 16-45 shots were
45mm 1/60 F4 ISO 100 & 45mm 1/125 ISO 800 F8.

The info about the comparison between PS & SLR apertures was helpful, thanks.
when you resize, do you atleast keep the "quality" at 100% (i think #14 or 12 in the photoshop slider)


now for the depth of field part, @ F4 and the distance i'm guessing you were shooting at, not everything will be in focus, but only specific parts within a given focus corridor (often refered to as "depth of field")

since your point and shoot is "effectivly" shot at a very small aperture, everything is in focus.

photographing roofs, at an angle, with (relativly) shallow depth of field, is ofcourse going to give you crappy results.


if you really want to run comparison tests, shoot a live subject, at 90* angles.

or do a little kitchen setup with a teapot and some flowers.


also, you shot the last shot at ISO800, and i presume no flash? Go and try that with your point and shoot...
01-19-2009, 10:11 AM   #7
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QuoteOriginally posted by holdgaj Quote
DO you mean the on-camera Jpeg ? I shoot in Raw & then use the Pentax utilities to create the Jpegs - are the Pentax utilities also poor performers ?
pentax utilities are very badly designed.

third party programs are much better with workflow and what not.

my weapon of choice is Lightroom (you can download a free 30 day trial, its only 120 megabytes, and then you can either buy or ..... an authorization key)
01-19-2009, 10:34 AM   #8
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Cheers, I get the point re the PS SLR comparison & the also the SLR depth of field issue. My issue is that I can't seem to get a sharp shot with the 16-45 no matter what I do. I was trying (seemingly badly) to illustrate this with the test shots. I'll take some others & post those. BTW I'm not trying to push the Canon P&S over the Pentax - I just did not know the aperture comparison was not valid - I'm new at this ! I was wondering why the DOF was so deep ! I'm very pleased with the camera, just trying to establish if I need to return the lens or not !

Thanks for your kind advice.

01-19-2009, 10:37 AM   #9
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One other thing I notice about the images - the P&S shot is at a much lower magnification on screen than the others. You need to compare at the viewing size, not at 100%. So when comparing the shots, make sure that you view the whole image at the same size as from your point and shoot when you compare. You should have a much better image at a given magnification from the dSLR. (anybody's).
01-19-2009, 10:45 AM   #10
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QuoteOriginally posted by holdgaj Quote
Cheers, I get the point re the PS SLR comparison & the also the SLR depth of field issue. My issue is that I can't seem to get a sharp shot with the 16-45 no matter what I do. I was trying (seemingly badly) to illustrate this with the test shots. I'll take some others & post those. BTW I'm not trying to push the Canon P&S over the Pentax - I just did not know the aperture comparison was not valid - I'm new at this ! I was wondering why the DOF was so deep ! I'm very pleased with the camera, just trying to establish if I need to return the lens or not !

Thanks for your kind advice.
if you want to test your lens for absolute sharpness

you have to first use a tripod

then you have 2 types of shots

a parallel wall shot, or a newspaper shot (ie, have your camera positioned parallel with a 100% flat object, such as a wall, or a newspaper spread on a wall) and you take pictures of that, that way you can guage corner-to-corner sharpness, distortions, softness, etc.

then you have a 45* degree test, known as a "front-back focus chart), where you photograph a specially designed chart at a 45* angle to determine if what your lens is telling the camera is what is actually happening (but this is a rare case practically)

remember that under certain circumstances it is very easy for a point and shoot to mimic or even surpass a DSLR in "quality"
01-19-2009, 10:47 AM   #11
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Well hang on, we're being a bit unhelpful. f/4 is about right as compared to f/8,
sweet spot for both lenses. The user has a right to compare the gear.

Do us a favour, set up a flat target (most use brick walls) and set up a tripod, make sure it's square (this is vital).

Fire off a few frames and re-sample the images to the same size (downsample the largest file to match the smaller one) then cut a crop from the centre at 100% magnification.

Here is an example i did recently with an unideal subject but you get the drift ....

D80 (10mp)



K100D (6mp)

01-19-2009, 10:49 AM   #12
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Oh and set your exposure as close as you can, the Canon is exposing a solid 2/3 stop darker and it makes the shingles and sky look more defined.
01-19-2009, 10:51 AM   #13
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QuoteOriginally posted by holdgaj Quote
I can't get a sharp image to save my life. I've adjusted the exposure bias using charts downloaded from this site - and it was a bit front focused - I adjusted it with a compensation of -2. Do I need to send it back ? Or am I expecting too much ?
I have a 16-45mm and a 50mm. The two are quite close in resolution, with the 50mm being slightly better. I suggest you forget about the focus adjustment until you figure out exactly what's going on.
01-19-2009, 10:53 AM   #14
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I'm not sure what we're supposed to be abe to tell from the last two images - they are blwn up much bigger than the first two. Blow the first one up as big as the last and then you'd have a comparison. As it is, I can only mention some very general things:

- Any P&S is going to be applying heavy contrast enhancement and sharpening in its JPEG processing. If you prefer that look, you'll have to do the same in your own processing. You can do that by turning up the in-camera contast & sharpness controls - even though it doesn't affect the RAW image itself, the pentax software will use those settings to set its own defaults. Or you could turn up the defaults.

- Depth of field on your P&S is practically infinite at f/4. Everything will be in sharp focus. On the DSLR, f/4 is nowhere near enough to render that entire building in focus. Part of it ill be sharp, part won't - that's the nature of shallow DOF. So it will be important to figure out which part of the building is in focus and compare only that.

- f/4 is wide open for the 16-45. No lens is at its best wide open.
01-19-2009, 10:53 AM   #15
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QuoteOriginally posted by Alfisti Quote
Well hang on, we're being a bit unhelpful. f/4 is about right as compared to f/8,
sweet spot for both lenses. The user has a right to compare the gear.
you cannot compare a point and shoot at F4 and an SLR at F4

because the point and shoot will have a very large depth of field corridor and the SLR wont, so it will be very easy to interpret the SLR shot as washed out or blurry compared the point and shoot, particulary when you shoot a complex geometrical structure with defined shapes like the OP did, especially since he decided to shoot it an angle.
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