Go Back   Steve's Digicams Forums > Digicam Help > What Camera Should I Buy?

Reply
 
Thread Tools Search this Thread
Old Dec 12, 2006, 9:20 PM   #1
Senior Member
 
Corpsy's Avatar
 
Join Date: Dec 2005
Posts: 879
Default

While I'm aware of most of the advantages and disadvantages of these two cameras, there is one area where I'm still not clear which is superior; low light performance.

Originally, I was thinking that the K100d would have an edge due to the SR which allows for slower shutter speeds. However, I've seen a few examples that seem to suggest that the sensor on the XT is significantly more sensitive than that on the K100d, such that it can use shutter speeds that are over twice as fast to achieve the same exposure when all other settings are the same.

I have not been able to establish this definitively as I cannot compare the two cameras side by side (no stores in the area have both), and the examples I've found weren't direct comparisons.

Here are the primary examples I'm looking at:

http://www.imaging-resource.com/PRODS/EXT/EXTPICS.HTM
http://www.imaging-resource.com/PRODS/K100D/K100DA5.HTM

On each of these pages, if you scroll down you can find a chart that shows how the camera performs in different low light setups at different ISOs. The problem is that the K100d is apparently shot at 18mm, f3.5 (probably the kit lens), and the XT is shot at 34mm, f2.8 (probably not the kit lens). I'm not sure which would have the advantage due to the lens differences.

However, assuming the difference is minimal, at a light level of 11 lux the K100d has to shoot at 1/5 sec at ISO 1600 to get a proper exposure. The XT shoots at 1/13 sec at the same ISO to achieve proper exposure. This suggests that the XT is over twice as bright. Factor in that the XT has much lower noise levels at ISO 1600 than the K100d and there appears to be a huge difference.

I'm wondering if anyone can shed some light on this, if perhaps I'm not reading the data correctly, or if someone can compare the two directly to confirm whether or not this is true, it would be extremely helpful.

It won't necessarily be the deciding factor though. Even if the XT outperforms the K100d in this regard, I might prefer to get the K100d and put the money I'd save towards a 50mm/1.4 which would likely trounce the XT's kit lens. I just want to make the most informed decision I can.

Thanks
Corpsy is offline   Reply With Quote
Sponsored Links
Old Dec 12, 2006, 10:04 PM   #2
Senior Member
 
mtclimber's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 18,143
Default

Corpsy-

Beacause I am not a professional camera review person, I cannot offer you various charts and graphs to validate my "findings." However, simply from the point of view of a long term (50+ years) as photographer, using bothfilm and digital camera technology.I feel that, with the proper post processing, the Pentax K100D and K10D images marginally surpass the images produced by Canon 350D and 400D cameras. But the margin is razor thin.Yes, I indeed realize that the Canon brethern will most probably rush forward to dispute my claim. However, if one were to look very closely indeed at the IQ from both brands, the Pentax images will win by a very slight margin. The difference is not very large at all. And, indeed any evaluation is tinged with personal preference.That IQ is a tribute to the high quality of all of the consumer DSLR cameras being offered today.

But please keep in mind that the differences between the Canon XT, XTi, The Nikon D-40, D-50 and even the D-80, along with the Pentax K100D and K10D are verysmall. In fact, we urge all camera fans who are interested in DSLR cameras to handle and use every one of the consumer DSLR cameras. They are ALL GOOD.

In the end, you will choose the DSLR camera that works best for you. But please keep in mind that the differences are indeed, quite small Almost infinitely small.

Yes, the grip might differ, the Burst Mode might differ, but in the final analysis, there will only be very, verysmall differences. You can't hardly go wrong with any of the consumer level DSLR cameras.

I only urge you, to get out there, taking those great photos. It is fun, and all of us want to see your results.

MT/Sarah
mtclimber is offline   Reply With Quote
Old Dec 13, 2006, 2:12 AM   #3
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

Allow me to borrow from Irwin Puts:

Quote:
Camera + sensor + lens + image capture + preprocessing + compression + reconstruction + post processing. Thus now we have an equation with eight variables, that are partially interdependent.
http://www.imx.nl/photosite/leica/m8_3/m8part3.html


When we consider the number of variables in the imaging chain and of course add color management and printing we have 10 variables in the chain from capture to final output. Add in the photographic style of the photographer for an important 11th variable which I would maintain can have a perceptible effect on final image quality.

Doing precise comparisons across so many variables in uncontrolled conditions is essentially futile. I have no doubt that Sarah is being truthful and honest that with her workflow and lens collection and cameras and printers that she feels she gets slightly better images from the Pentax.

I also have no doubt that simply by changing photographer it might go the other way. Certainly by changing lenses, and post processing and printers and paper things could move in any direction.

I believe we have certainly reached a position where the camera is unlikely to be of primary significance in determining image quality in any given market segment. However there are quite significant differences between cameras nevertheless, some praise the ergonomics of Nikon above all others, others find compelling the argument that putting image stabilisation in the camera body is cheaper in the long run. Others find the strength of the Canon system taken as a whole to be more significant. All of these matters are endlessly debatable.

I often think of photography as two distinct but related disciplines (or hobbies if you like where amateurs are concerned) the first is the interest in the engineering aspects of cameras and lenses and film or digital processing. The second is the business of creating beautiful or challenging images. Excellence in one field is no guarantee of much ability in the other field at all. Just popping down to one's local camera club often introduces one to a great many technical experts whose photographs are singularly dull and uninspiring. Popping into the art department of a local university often unearths talented young artists who hardly know one end of a camera from the other.

In the final analysis you need to balance the features and ergonomics of a camera system against your needs. Ebay means the decision is no longer as economically significant as it used to be. If you make a mistake, it's not likely to be too expensive to switch systems at a later date.
peripatetic is offline   Reply With Quote
Old Dec 13, 2006, 6:30 AM   #4
Moderator
 
Join Date: Aug 2004
Posts: 8,529
Default

Corpsy,

I'll cast another vote for: you're not likely to gain a noticable edge in high ISO performance from either camera.

As suggested by peripatetic, your decision should be made based on the other attributes of the cameras and, more importantly, based upon the two systems and where you envision your photography taking you in the next 10 years. As mentioned, it gets very costly to switch systems once you invest in lenses. So, with a mind for the types of lenses you may want to buy a few years down the road, look at whether either system has what you're looking for. In this regard, each system has it's advantages. Pentax cameras can use any pentax lens out there - so you can find used lenses at good prices if you look. Canon on the other hand has a much larger selection of newer auto-focus lenses available.

As stated, you're already aware of the feature differences in the specific cameras - but consider the SYSTEMs as a whole - you're buying into a system not just a single body.

The good news? Both cameras are excellent performers. So, in the short term there really isn't a wrong answer. Long term? It depends on which system has the offerings that most match YOUR specific needs. For some people that's Pentax. For others it's Canon.
JohnG is offline   Reply With Quote
Old Dec 15, 2006, 5:54 PM   #5
Senior Member
 
terry@softreq.com's Avatar
 
Join Date: Jun 2004
Posts: 2,539
Default

To me the true test of a camera is how "clean" the images are at high ISO's, and performance, ie. lack of shutter lag.

Beyond that, there are many variables as Peri... pointed out.

Here's another way of looking at it... Figure out which lenses you'd like to use, then buy the body that fits them
-- Terry
terry@softreq.com is offline   Reply With Quote
Old Dec 17, 2006, 11:05 PM   #6
Senior Member
 
Corpsy's Avatar
 
Join Date: Dec 2005
Posts: 879
Default

Thanks for the responses. Sorry it took me so long to get back to you. I was kind of hoping someone could give me a definitive answer, but I did the best I could in my own research.

My problem is that I frequently find myself in shooting situations that push a camera to one extreme or the other. Mostly, that would be shooting nature at extreme telephoto, shooting in very low light situations, or both. I'm just trying to figure out which camera will allow me to shoot in as many situations as possible, not necessarily which one has the highest quality images.

As far as I can tell, there's not a huge difference in quality anyway, especially if you shoot in RAW. Noise levels are pretty close, though the in-camera processing of the XT is better at cleaning it up than the K100d's. Again, not important if you shoot RAW.

From the research that I did, I compared as many images as possible where a scene was photographed in the same light with both cameras. In every instance where the lighting situation was relatively well controlled, the XT was at least twice as bright, meaning that at the same ISO and F-stop, it could use a shutter speed at least twice as fast. This occurance appeared consistantly in every case where it seemed a fair comparison could be made, which typically meant I was looking at JPGs taken directly from the camera unprocessed. I suppose it could have been a coincidence, but I doubt it.

If I was mostly shooting action photography, this would put the XT well over the edge as it already has the advantage when it comes to continuous shooting and better JPG processing. However, while I do find myself shooting in burst mode from time to time, it's usually to compensate for the fact that my FZ30 would blur 2 out of 3 shots at extreme zooms in low light.

As far as I can tell, the XT still has a bit of an advantage when it comes to wide angle, low light photography. Given the choice between shooting 1/30 without SR or 1/15 with, I'd rather have the extra speed. That advantage seems to disappear at telephoto as it appears many photographers get consistently good results at 200m and beyond at 1/15 or slower with the K100d. I've shot without SR at 200m and probably wouldn't go slower than 1/60. While extra speed is still more desirable, I'll take the camera that can actually pull off the shot.

Finally, the Pentax just seems like more bang for the buck. I already have SD cards and NIMH batteries, the kit lens is better than the XT's, and I like the idea of having so many cheap, used lenses available. I'll be keeping an eye out for after Christmas sales while the $50 rebate is still valid.

Thanks again.


If anyone's interested in seeing how I came to my conclusion about low light, I looked at the EXIF data on the two comparison shots here:
http://www.dpreview.com/reviews/pentaxk100d/page19.asp

As well as the studio shots here:
http://www.dcresource.com/reviews/pentax/k100d-review/
and here:
http://www.dcresource.com/reviews/ca...ew/index.shtml

And the low light test shots here:
http://www.imaging-resource.com/PRODS/K100D/K100DA5.HTM
and here:
http://www.imaging-resource.com/PRODS/EXT/EXTPICS.HTM

For any instances where F stops didn't match, I went here to calculate the difference:
http://www.robert-barrett.com/photo/...alculator.html
Corpsy is offline   Reply With Quote
Old Dec 18, 2006, 12:41 AM   #7
Senior Member
 
Join Date: Aug 2006
Posts: 822
Default

I think much of the difference you are seeing is explained here:

http://www.dpreview.com/reviews/pentaxk100d/page14.asp

The 350D ISO settings are apparently more sensitive than labeled, thus:
100=125
200=250
400=500
800=1000
1600=2000


kenbalbari is offline   Reply With Quote
Old Dec 18, 2006, 8:22 AM   #8
Senior Member
 
Corpsy's Avatar
 
Join Date: Dec 2005
Posts: 879
Default

I've seen that as well. It's the only instance where I've seen information like that, but I've seen multiple cases where the XT captured the same exposure 200-225% faster than the K100d. As they don't provide any examples with EXIF data to demonstrate their claim, I'm more apt to believe the EXIF data of images I have seen.

I am hoping to get the chance to compare them side by side at some point. As soon as the only store within 100 miles gets XTs back in stock I'm planning on comparing it side by side with the Pentax to see if there is such an extreme difference in sensitivity. Though I already made my choice, I'm still curious and if the XT gets real cheap, I could change my mind.
Corpsy is offline   Reply With Quote
Old Dec 18, 2006, 5:16 PM   #9
Senior Member
 
Join Date: Aug 2006
Posts: 822
Default

Quote:
I've seen that as well. It's the only instance where I've seen information like that, but I've seen multiple cases where the XT captured the same exposure 200-225% faster than the K100d. As they don't provide any examples with EXIF data to demonstrate their claim, I'm more apt to believe the EXIF data of images I have seen.
Well now that I take a closer look, I see you're absolutely correct. Just taking a look at the ISO1600 samples from dcresource, I notice the following groups:

Group A (-2/3): 1/125 f5.6, 1/100 f6.3, or 1/60 f8.0
Nikon D80, D40, Pentax K100D

Group B (-1/3): 1/160 f5.6, 1/125 f6.3
Olympus E500, E330

Group C (+0): 1/200 f5.6, 1/125 f7.1, 1/100 f8.0
Canon XTi 400D, 30D, Nikon D200

Group D (+1/3): 1/250 f5.6, 1/200 f6.3, or 1/125 f8.0
Canon XT 350D, Sony A100, Nikon D50

Group E (+2/3): 1/160 f8.0
Nikon D70

Note that the two main groups above are A and D. And that there's exactly a full stop difference there. Group D is exactly twice as sensitive as group A. The Olympus Cameras are about a third of a stop more sensitive than group A, and the D70 is about a full stop ahead of that. And the XTi, 30D and D200 are only about a third of a stop less sensitive than group D.

I only looked at one sample shot here though, so it will be interesting if these groups hold up. But it appears that ISO 1600 on the Pentax and newer Nikons would be more equivalent to ISO 800 on the older D50 or Rebel XT.

On edit- I decided to rather arbitrarily assume that the middle group was the "correct" one, just so I could label the groups as 1/3 stop differences. I think it makes it a bit easier to understand.

kenbalbari is offline   Reply With Quote
Old Dec 18, 2006, 6:02 PM   #10
Senior Member
 
Corpsy's Avatar
 
Join Date: Dec 2005
Posts: 879
Default

Thanks for the additional research. I think this data could be extremely helpful to people researching cameras. I got into the habit of comparing camera image quality by looking at the noise levels at the same ISO. It turns out if you're trying to decide between a Nikon D40 and a Canon Rebel XT, you'd need to compare ISO 1600 images from the D40 to ISO 800 images on the XT to get a truly fair performance comparison.

I really appreciate how comprehensive your list is. I was very interested in the Sony Alpha until I saw the high noise levels at higher ISO. Now that I see it's twice as sensitive as the K100d, that pretty much evens out performance-wise, even though it's much higher resolution. And considering the Alpha has most of what I like about Pentax plus better overall performance and a dust removal system, I might just have to wait until that one comes down in price a bit. It'd be hard to get over my anti-Sony bias though...

Thanks!
Corpsy is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 11:55 PM.