Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-14-2010, 07:07 AM   #16
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
QuoteOriginally posted by phzy2003 Quote
yes, kx is very easy to highlight clips, it is got very good dark but not highlight
Just give it a -0.7 exposure compensation in bright light and -0.3 in less-than-bright light. The fact that you can have the same DR with negative exposure compensation can be seen as an advantage: it makes your lenses act as if they were faster than they are (in fairly good-but not-bright-light). Even in very good light, the wonderful DA L 55-300mm can use all the additional light you can give it at 300mm.


Last edited by causey; 05-14-2010 at 11:50 AM.
05-15-2010, 01:13 AM   #17
Senior Member




Join Date: Apr 2010
Location: Los Angeles
Photos: Gallery
Posts: 172
I'm a bit confused about dynamic range as it relates to camera exposures. Let's say a Nikon shoots an image of a contrasty scene and neither highlights nor shadows are clipped. Then a Pentax shoots the same scene and both highlights and shadows are clipped. Since the Pentax in this example is capturing more zones along the continuum of black to white (blacker blacks and whiter whites), why can't we say that the Pentax has greater dynamic range than the Nikon? Alternately, if we are shooting with shadow and highlight correction on, haven't we, in fact, reduced the dynamic range, making the image less contrasty? It seems similar to the current trend in popular music production to over-compress songs (reduce the dynamic range) to make the sound more friendly for earbud and car radio users. Where has my thinking gone astray here?
05-15-2010, 01:45 AM   #18
Veteran Member
Eruditass's Avatar

Join Date: Jul 2009
Location: Pittsburgh, PA
Photos: Gallery | Albums
Posts: 2,206
QuoteOriginally posted by lectrolink Quote
I'm a bit confused about dynamic range as it relates to camera exposures. Let's say a Nikon shoots an image of a contrasty scene and neither highlights nor shadows are clipped. Then a Pentax shoots the same scene and both highlights and shadows are clipped. Since the Pentax in this example is capturing more zones along the continuum of black to white (blacker blacks and whiter whites), why can't we say that the Pentax has greater dynamic range than the Nikon? Alternately, if we are shooting with shadow and highlight correction on, haven't we, in fact, reduced the dynamic range, making the image less contrasty? It seems similar to the current trend in popular music production to over-compress songs (reduce the dynamic range) to make the sound more friendly for earbud and car radio users. Where has my thinking gone astray here?
That's not the dynamic range. The dynamic range is the difference between the brightest and darkest tone in the real world as measured by a light meter, and not in the picture.

Basically, Nikon would be essentially be doing a bit of shadow and highlight compensation.

All pictures have the same range of values from light to dark available in a JPEG. The higher the dynamic range, the more you squeeze into there. It is worthwhile to do this as you can adjust the contrast as you like easily, but once detail is clipped, it's gone.

It's like being digitally clipped in an mp3... ever hear that?
05-15-2010, 01:47 AM   #19
Veteran Member
Eruditass's Avatar

Join Date: Jul 2009
Location: Pittsburgh, PA
Photos: Gallery | Albums
Posts: 2,206
QuoteOriginally posted by causey Quote
Just give it a -0.7 exposure compensation in bright light and -0.3 in less-than-bright light. The fact that you can have the same DR with negative exposure compensation can be seen as an advantage: it makes your lenses act as if they were faster than they are (in fairly good-but not-bright-light). Even in very good light, the wonderful DA L 55-300mm can use all the additional light you can give it at 300mm.
Exactly, give a bit of negative EC and it beats many other APS-C cameras in highlight range.. post-process to taste, of course.

05-15-2010, 02:31 AM   #20
Senior Member




Join Date: Apr 2010
Location: Los Angeles
Photos: Gallery
Posts: 172
still not really understanding DR. Are you saying that a photo with both shadow and highlight compensation turned on has greater DR than one without? Is DR essentially a measure of detail available at both ends of the histogram? I know that clipping (i.e. going off the ends of the histogram) means loss of all detail; so does it then follow that the histogram- from left to right- is a measure of total possible dynamic range that still has details (not clipped)? If yes, then if a camera image can deliver a contrasty scene with a histogram that extends from extreme left to extreme right, does that mean the camera has the ultimate dynamic range? What would the differences look like in a histo of same scene between a camera that has great DR vs one that has lousy DR?
05-15-2010, 05:27 AM   #21
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
Dpreview and other review sites propagate this confusion... To put it in very simple terms: imagine a line drawn on a sheet of paper. Now imagine that two points on that line, one on the left of the origin (point zero), the other on the right of the origin, determine a segment--let's say that segment represents the DR of a certain camera. The negative values (left of origin) represent degrees of shadows, while positive values (right of origin) represent degrees of highlights.

What really matters is not where the origin lies in relation to the extremities of the segment, since we have control over where the origin is placed--you can move it in both directions, if you'd like--but the length of the segment. Various cameras have various DR, and some better than others in this respect, meaning that the segment that represents their DR is longer than the segment representing other cameras' DR. The only 'issue' with K-x is that the default origin has been placed nearer the 'highlights' end. (Other cameras do that as well, or clip shadows.) Again, by using negative exposure compensation, you can easily deal with this aspect (not a real issue). Otherwise, if you shoot raw, you can retrieve all the detail which K-x is capable of retaining by underexposing in your raw editor. In any case, what appears as a washed out zone in a pic is only apparently washed out, because the detail is intact--you just need to retrieve it.

Last edited by causey; 05-15-2010 at 05:42 AM.
05-15-2010, 05:41 AM   #22
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
Here's a mathematical comparison of the property of various sensors which shows that K-x's DR is the same as Nikon D90's DR:

Compare cameras
05-15-2010, 07:18 AM   #23
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,631
QuoteOriginally posted by lectrolink Quote
still not really understanding DR. Are you saying that a photo with both shadow and highlight compensation turned on has greater DR than one without?
Dynamic range is the difference in wavelength and intensity between the brightest and darkest elements in a scene. Some scenes have too much DR for any camera to capture. They will not fit within the clipping limits shown in the Histogram. That's when D-Range corrections come into play. Highlight compensation reduces the sensitivity of the sensor to bright light. Shadow correction compresses wavelengths at the extreme left end of the histogram (makes dark colours/shadows less dark). Highlight and shadow compensation reduce the dynamic range of the scene, hopefully enough that it can be recorded without clipping (not always possible, even with a full-frame camera and D-Range correction.)

Highlight clipping with the K-x is not due to inferior dynamic range. Its available DR is as good as any APS-C camera, and better than most. Highlight clipping occurs because that's the decision Pentax made with this particular camera. They have programmed the metering system to expose more brightly vs previous Pentax cameras. Many basic level dslr's are balanced to clip highlights, as are all p&s cameras. Novices generally prefer this look, because it exposes Uncle Fred against a bright sky better in Auto mode, at the cost of blown sky detail. A more experienced photographer would take control of metering the scene and expose it his/her taste by using exposure compensation or changing the way the scene is metered (CW, spot, AE-L) or by using fill flash. For a landscape shot HDR or a GND filter helps control DR.

Criticism of clipped highlights on a K-x is a cheap shot. Pentax could have chosen to apply D-range correction to jpegs like many 4/3 and M4/3 cameras, but that's a trick to make up for lack of true dynamic range. Pentax left the control in the hands of the photographer where it belongs, while simutaneously tweaking the exposure to the right. It's not surprising they did this, because of the intended market for the low cost K-x, and because disingenuous or ignorant magazine reviewers insisted on criticizing previous Pentax dslr's for underexposing. It appears Pentax will be criticized by some reviewers no matter how they set exposure.

05-15-2010, 01:00 PM   #24
Veteran Member




Join Date: Sep 2007
Location: USA
Posts: 1,812
QuoteOriginally posted by trailrider Quote
I am new to the forum and considering a K-X purchase. I have read the review at dpreview. I am especially interested in the dynamic range test.
Pentax K-x Review: 17. Photographic tests (DR): Digital Photography Review

Do people feel the following comment is accurate? If so can it be overcome via adjustments in pre and post processing?

"The K-x has a fairly pronounced tendency to clip highlights and over exposed parts of the image are usually not recoverable at all or produce false color information when negative digital exposure compensation is applied in a RAW converter."
That's pretty accurate comment -
however as many others pointed out the overall Dynamic Range of the Pentax K-x is about the same/comparable to other cameras compared -
it's just that K-x has less range above mid-gray and more extended below mid-gray.

It's more the fact the Pentax K-x has a tendency to "over-expose" under certain conditions -
now this could be either a good thing or a bad thing.

If one is looking strictly at the highlights - then it sounds like a bad thing - as they will tend to get blown out.

However mostly in my experience for general photography I am mainly not that interested in the highlights but in the mid-tones of the main subject -
this means I'd much prefer that the camera exposes for the main subject possibly sacrificing any highlight -
in fact I'd get annoyed if the camera exposed for the highlights -
I would feel that it was "fooled" by the highlights -
and underexposed the shot!

Having said that the Pentax K-x has one of the widest Dynamic Ranges of any APS-C sensor camera, and this is confirmed by the DxO camera rankings (may have to select APS-C sensor size).

BUT the K-x has less room above mid-gray and more room below mid-gray - so yes the higlights will tend to be a bit more overexposed from mid-gray than with another camera - but the difference will tend to be fairly minimal - unless of course one is doing more high-key photos.

I shoot in sometimes wildly varying light conditions - eg: music concert photography where the lights can change all the time.

What I do the "protect" the highlights is to shoot mostly -1/3 stop compensation, and with the Highlight Correction On - this does not prevent over-exposure of the highlights - but mostly I find this setting good for my shooting.

For example last night I was shooting Little Feat -

(note: no adjustments of brightness/contrast in editor, just resizing then sharpening)
even with my camera settings this is obviously over-exposed for the main subjects - it really couldn't be helped because of the changing lights and wide-wide dynamic range - the K-x did its best be obviously could not read my mind to where the main subject/important area was.

Once I saw the shot - advantage of the much mis-maligned "chimping" -
I quickly set my exposure compensation to -1 stop - resulting in:

which is much better - seems a nice compromise between the main subjects and the stage lighting which in a way is the overall/main attraction.

However it was not perfect -
even with -1 stop compensation I still got:

this really shows how dynamic the stage lighting was - this was literally only seconds apart from the shot above - yet the performers to the left are over-exposed - while to the right - they are about the same as the shot above.

Reading this:
QuoteOriginally posted by er1kksen Quote
What you need is a program like ACR or lightroom with a "recovery" slider, which allows you to bring the highlights back down while keeping the rest of the exposure at normal levels.
I tried this - my shots are in JPG - but I used Open As... (camera RAW) in PS Elements 7.0 on the file - so invoked ACR 5.6 and used the Recovery slider - and managed to get this for the first shot posted:

not great, but somewhat better than the first shot.

RAW may have done better having more flexibility -
but this will do.

Thanks er1kksen.

Photos from the Little Feat gig - link to first pic (30 more)

Last edited by UnknownVT; 05-15-2010 at 05:10 PM.
05-15-2010, 07:39 PM   #25
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
For all those who are discussing the dynamic range of the sensor or camera , as opposed to discussing someone elses reports go out and test your own camera.

To do this start with all the settings (jpeg) set to neutral, the camera set to 1/30 and meter the scene. Without changing aperture shoot a series of shots starting at 1/4000 down to as long an exposure as possible in 1/3 stop increments. Your test subject is the most boring of subjects, a block wall. Then using a photo editor measure the grey scale average value for each shot and plot this against the exposure with exposure in time on the x axis on a log scalle.

This will show the dynamic range of the sensor.

If you repeat this at minimum and maximum contrast, and with highlight and shadow preservation on, you will see exactly how detail is compressed

I have done this and reported it in the past.

With respect to exposure bias each camera maker has a different approach and as a result it is up to the photographer to do a trial on his kit to understand how it works. Tests can always be designed to identify weakness but understanding your cameras bias willhelp you take better exposed shots.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, k-x, photography, range, review
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K5 highlight headroom? kenyee Pentax K-5 10 11-07-2010 01:54 PM
Pentax K-x single channel clipping gaeriel Pentax DSLR Discussion 8 09-20-2010 02:27 AM
K-x highlight correction LN108 Pentax DSLR Discussion 6 07-17-2010 01:48 AM
Clipping on CS3 netuser Digital Processing, Software, and Printing 4 12-23-2009 08:24 AM
Dynamic Range Extension Shadow Clipping in bokeh Katsura Pentax DSLR Discussion 6 12-21-2009 12:15 AM



All times are GMT -7. The time now is 03:34 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top