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09-22-2009, 10:42 AM   #1
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istDs - Questionable Image Quality ?

Last April I purchased a second-hand istDs via ebay as a replacement for a Canon A610 point and shoot. To cut a long story short I have always had mixed feelings about the istDs image quality and it is definition that I am most concerned about. I inherited a dirty sensor from the previous owner and had to have it professionally cleaned.

I enclose 3 images and would ask people to comment on the questions which follow. Images 1 & 2 were taken with the kit 18-55mm DA lens. I've had to cut the size down to 800x600 so it can be a little hard to tell.

Image 1 – The tell-tale problems are in things like the lettering on the ferry. ‘calmac’ is against a white background and the line between the letter and the background should be sharp. Instead it is slightly blurred/blotchy causing the loss of crispness. This applies to many of the things in the photograph, the people etc. Also the number plate on the car should be clearly visible.

Image 2 – taken in relatively low light. The result is blotchy, particularly the reddish flower in the centre.

Image 3 – similar to image 2 but taken with the Canon point & shoot. I think this image is better.

1) General comments on image quality.
2) Do you think there is a problem or am I expecting too much from the camera. Previous to the Canon I had a Pentax KM which was used for 30 years, say no more on image quality !!! This may have spoilt me.
3) If you think I have a problem with the camera what do you think it is and how might I rectify it.

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PENTAX *ist DS  Photo 
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09-22-2009, 11:20 AM   #2
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At the posted sizes, it's impossible to see any of the issues you are talking about. You'd be better off posting crops showing just the specific problem areas, but leaving them full size rather than having them resized as you do here. In other words, post what are called "100% crops" - crops that have not been resized. It's impossible to tell at this size if the car even *has* a license plate, for example., much less how sharp it is?

But speaking generally:

- Do you know for sure where the camera focused on #1? If it wasn't right on the letters, then I wouldn't expect them to be completely sharp. And if it did focus there, then I wouldn't expect the people to be equally sharp - they are closer.

- The EXIF is missing from the Canon shot, so it's hard to know if it was an apples-to-apples comparison in terms of the ISO you used.

- If you had a filter on the 18-55, that explains some loss of sharpness right there.

- If you shot JPEG, you can experiment with different setings (eg, Natural versus Bright, turning up the Sharpening setting) to see if one combination looks better to your eyes than another. If you shoot RAW, you would do the same in your RAW processing program. Sharpening doesn't come for free - createing really sharp edges often creates artificial "halos" around objects - and the DS tends to be pretty conservative about sharpening by default, whereas most P&S cameras tend to oversharpen by default.

But bottom line, again, at the post size, it's really impossible to say.
09-22-2009, 11:26 AM   #3
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The flower image is very saturated, which will mask the detail. What post processing software are you using ?
09-22-2009, 02:00 PM   #4
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Many thanks for your replies.

Apologies for that. It's like trying to see the impossible.

I enclose 3 crops from a 100% image. Same questions apply.

No post-processing software has been used. Images are straight off the memory card.

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09-22-2009, 05:10 PM   #5
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Also - have you got the jpeg settings to their best (3 stars from memory) and biggest (3000x2000)
09-22-2009, 05:39 PM   #6
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I see your first image was shot at ISO800. You are probably expecting a bit too much from shooting at high ISO with an old camera... Try ISO of 200 (I think that's lowest on your model?) - might turn out to be better!
09-22-2009, 07:04 PM   #7
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For the first generation kit lens, shooting at ISO 800, and with no additional sharpening applied, that looks about right to me. If you prefer the heavily edge-sharpened look typical of P&S cameras, you can certainly turn sharpening up in camera, or apply more in PP, but do watch out for the artifacts that inevitably result. For the flower picture, I'd say it looks like you shot at too low a shutter speed for the focal length. At 31mm, you should have been at least 1/45" (1 / FL*1.5) at the bare minimum, and even that isn't an ironclad guarantee of avoiding camera shake, especially if you're pixel peeping at 100% like this.
09-23-2009, 09:43 AM   #8
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I think you expect too much. Can you offer a 100% sample of exactly same scene with istDs and another camera wich you think pictures the scene correctly. The number plate, lines and similar stuff are on the boundary on sensor resolution. You could do better with RAW conversion, since Pentax has more focus on general image sharpness when other RAW converter focus on fine detail.

In what way the image nr 3. is better?
To me the grass seems like a messy porridge, when you can distinguish individual haulms and flowers in the istDs shot. Building walls are washed out, white areas where istDs shows coloured and fine texture.

It is known that colourfull detail can get oversaturated with Pentax bright colour scheme if your'e talking about the loss of detail in the red flower. This can be easy avoided by turning down saturation or doing apropriate RAW conversion, as i've done in here:
https://www.pentaxforums.com/forums/post-processing-printing-software-darkroo...-raw-2.html#20

09-23-2009, 10:05 AM   #9
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I've owned a DS in the past - my first Pentax DSLR.

When shooting RAW with a top notch lens, the DS can produce beautiful images right out of the camera. Everyone seems to have covered the bases in what to suggest or consider.

Regards,
Marc
09-24-2009, 10:47 AM   #10
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I second what Marc said. I also owned an *ist DS and was very happy with the results - which did vary somewhat based on what lens I was using - and I mostly shot jpg's. I did try to keep the ISO setting no higher than 400 as grain would start to appear at higher ISO settings.
09-24-2009, 02:25 PM   #11
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QuoteOriginally posted by JeffT Quote

I enclose 3 images and would ask people to comment on the questions which follow. Images 1 & 2 were taken with the kit 18-55mm DA lens. I've had to cut the size down to 800x600 so it can be a little hard to tell.

Image 1 – The tell-tale problems are in things like the lettering on the ferry. ‘calmac’ is against a white background and the line between the letter and the background should be sharp. Instead it is slightly blurred/blotchy causing the loss of crispness. This applies to many of the things in the photograph, the people etc. Also the number plate on the car should be clearly visible.

Image 2 – taken in relatively low light. The result is blotchy, particularly the reddish flower in the centre.

Image 3 – similar to image 2 but taken with the Canon point & shoot. I think this image is better.
image 2 looks way better than image 3. the rose saturation aside (not sure i can comment nor necessarily see the issue), there is so much moe detail in #2, particularly when you compare the chicken wire grid and the blades of grass which are nonexistent in the P&S camera. #3 is way over saturated, IMO.

#1 - i didnt look up the EXIF here but the other poster said ISO800 which is pretty high for that camera. Also as Marc asked, were you auto or manually focusing on the website address in particular, or some other part of the scene. the whites look blown out in general so it is conceivable that the white surrounding the lettering has blown a bit too reducing perceived sharpness. also, you caught so much of the foreground in focus, i wonder what aperture you were using and if the ship details were falling just outside your DOF.

Also, I was once a big fan of the DA 18-55 series one...until the moment i tried just about any other lens. I owned 2 copies of it and personally i think that could be the limiting factor in your IQ. still, these results are not bad at all and i dont think there is any problem with the camera based on what youve shown us.
good luck!
09-28-2009, 12:59 PM   #12
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If you shoot in jpeg, the ist series didn't have a very good jpeg engine yet.
The K1XXD series had the much improved jpeg engine and produced better results than the older ist series (for jpeg).
If you shoot RAW however, the results would just be the same for both (istDX & K1XXD) 6mp sensor.
09-28-2009, 03:17 PM   #13
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Well I've been using two DS's for over two years. I have never had a problem with jpegs.
I've shot everything from astro to macro. I will say, that the exposure has to be accurate. The " A ' setting is not infallible, It pays to get to know the quirks of the metering system.
Here are two of my jpegs. Just a touch of sharpening, and a tad contrast.



Last edited by wildlifephotog; 09-28-2009 at 03:31 PM.
09-30-2009, 02:28 PM   #14
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istDs - Questionable Image Quality ?

Thanks to everyone who replied to this post.

To summarise -
a) Don't go above 400 ASA
b) Make a preference for RAW
c) There is a question mark on the lens quality. However I came across -
Pentax *ist DS Review Samples Gallery: Digital Photography Review These have been taken with a DA 18-55 and if I could get that I'd be a happy bunny.
d) There does not appear to be a problem.
e) I wonder what lens wildlifephotog was using.
09-30-2009, 06:00 PM   #15
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Honestly I don't buy almost everything above. ISO800 is fine on this camera, the pixels are enormous. Reds are a bitch plain and simple as they get blown out by most cameras.

Image 2's issue is WB, it's too blue, play with it a little and it looks fine.

The kit lens, like all kit lenses, likes to be stopped down, make sure you are not shooting with the aperture wide open.

With a DSLR depth of field is MUCH more shallow, this is why aperture is vital and anyone using P mode is goign to hit a wall, you may be using A mode, i don't know TBH

This was shot with the kit lens ......

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