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06-14-2008, 11:12 AM   #31
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QuoteOriginally posted by Big Dave Quote
Steve,
Could the difference be the result of the so called digital coatings? The image appears slightly brighter to the metering cells which are optomize for these. This would account for the slight increase in exposure with film FF lenses. I did a test with my Nikon 55mm micro and my kit lens at 5.6 and 55mm with available light. The Nikon 55mm did have slightly greater exposure. This is why I like shooting with manual lenses at the working appeture. This allows the use of AV mode and shows actual depth of field during shooting. The exposure compensation is available in AV mode, where it isn't in manual. Auto diaphram is better for low light flash work of course.

Dave
I don't know Dave, the coatings probably reduce the light hitting the sensor a bit, but this isn't a metering issue. When you shoot in Manual with the same parameters dialed in you should theoretically get near identical images, you are bypassing the camera's auto metering completely, so the difference must be purely in the lens.

06-14-2008, 11:54 AM   #32
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QuoteOriginally posted by arbutusq Quote
I don't know Dave, the coatings probably reduce the light hitting the sensor a bit, but this isn't a metering issue. When you shoot in Manual with the same parameters dialed in you should theoretically get near identical images, you are bypassing the camera's auto metering completely, so the difference must be purely in the lens.
something to consider:
Microlenses. Remember the meter sees one light path. The sensor another.
Identical exposures can look different due to light scatter/beaming on the sensor plane. not to mention the effects of passing it through a penta/mirror/prism to a monochrome light meter..... Must be at least 10 things that would influence the image "quality" between the sensor and the light meter.....
curvature of lens field would make the contrast differences and exposure differences.
My feeling has always been the digital sensor is much more sensitive to these "geometry" anomolies than film/slides ever were.

Last edited by jeffkrol; 06-14-2008 at 12:04 PM.
06-14-2008, 11:54 AM   #33
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arbutusq,
I have always wondered about the differences between the way film and a CCD sensor handle an image. If the metering isn't the cause, it must be that the digital lenses transmit a brighter image to the sensor. I really haven't tried a test without using metering. Maybe I'll breakout my old external light meter. I'll have to find a battery for it though.

Dave

QuoteOriginally posted by arbutusq Quote
I don't know Dave, the coatings probably reduce the light hitting the sensor a bit, but this isn't a metering issue. When you shoot in Manual with the same parameters dialed in you should theoretically get near identical images, you are bypassing the camera's auto metering completely, so the difference must be purely in the lens.
06-14-2008, 12:05 PM   #34
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QuoteOriginally posted by jeffkrol Quote
something to consider:
Microlenses. Remember the meter sees one light path. The sensor another.
Identical exposures can look different due to light scatter/beaming on the sensor plane. not to mention the effects of passing it through a penta/mirror/prism to a monochrome light meter..... Must be at least 10 things that would influence the image "guality" between the sensor and the light meter.....
curvature of lens field would make th contrast differences and exposure differences.
My feeling has always been the digital sensor is much more sensitive to these "geometry" anomolies than film/slides ever were.
Good point, I should have said the lens and the sensor. I wonder whether the sensor is more sensitive or that we are able to see more differences with our computers and RAW than would have been easily seen with film.

06-14-2008, 12:26 PM   #35
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QuoteOriginally posted by arbutusq Quote
Good point, I should have said the lens and the sensor. I wonder whether the sensor is more sensitive or that we are able to see more differences with our computers and RAW than would have been easily seen with film.
Well to stress how different digital is from film you really must start at the RAW level.:
Notice how linear and dark the file is (composed of multi colored dots ) not to mention un color corrected. You know it still amazes me to the fact it really even works..
This really doesn't have much to do w/ exposure per se but it helps to see what your "negative" really goes through and how many places there are to "modify" it.
Raw File View
BTW: I never can get the TIFF's to just download. My browsers try to open them but fail. The thumbnails are fine for "educational" purposes.
And back to exposure from a 5D guy and a ETTR person.........
In the final analysis, ETTR isn’t about overexposure, but rather proper exposure, while avoiding true highlight clipping of linear-encoded data. This often isn’t the exposure our light meters recommend.
Exposing for RAW | Digital Photo Pro Magazine
Guess even those "perfect" 5D exposures can be improved..
There's more in that article like iso effecting contrast ect.
what more needs to be said.. just learn what your camera sees and does w/ each component. Expecting each and every lens/camera to behave
equally is, well, ridiculous. Now to be not a pure Pentax fanboy, there is room for improvement but we first must seperate MYTH from reality...

Last edited by jeffkrol; 06-14-2008 at 12:50 PM.
06-14-2008, 12:33 PM   #36
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QuoteOriginally posted by jeffkrol Quote
Well to stress how different digital is from film you really must start at the RAW level.:
Notice how linear and dark the file is, not to mention un color corrected. You know it still amazes me to the fact it really even works..
This really doesn't have much to do w/ exposure per se but it helps to see what your "negative" really goes through and how many places there are to "modify" it.
Raw File View
BTW: I never can get the TIFF's to just download. My browsers try to open them but fail. The thumbnails are fine for "educational" purposes.
I remember when i first started shooting RAW with an Olympus C5060 and I found a program that did a straight (unaltered) conversion, it was a dark gloomy mess. Its amazing to me that they can combine three black and white images (RGB) to gain all the wonderful gradations of colour. Yep we're a long way from metering now.
06-14-2008, 08:51 PM   #37
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I wish I had the expertise to discuss the technical aspects of exposure with you all, but I do not. But I would still like to contribute to this post, because I love and study photography with passion. I will start by saying I have grown to love my K20, but it has not yet proven to be the camera I hoped it would be. I accept my responsibility as a photographer to adapt, learn and work with the camera on its own terms.

My biggest concern with it is the inconsistent exposure results, particularly underexposure issues, for sure. I have been struggling to raise my skills to higher levels so I can overcome this obstacle. The trouble is, the camera is just too inconsistent with its exposure performance—it is that simple. I now have taken thousands of shots with it. I know a bunch of you will jump down my back now, claiming it is my incompetence which generates the exposure problems, but there is nothing I can do for you. The fact is a camera of this cost should not underexpose to the degree it does---PERIOD!

I sometimes wonder if Corporate Pentax people hang out here and jump on anyone faulting the camera, accusing them of incompetence. Yes, this is a silly notion, but no sillier than the notion that all the underexposure issues with the K20 are from user incompetence. BTW, this is a very good post!

Regards,


Ernest



Humanity subdues inhumanity as water subdues fire.

Mencius 6A:18.
06-14-2008, 09:05 PM   #38
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QuoteOriginally posted by Jewelltrail Quote
My biggest concern with it is the inconsistent exposure results, particularly underexposure issues, for sure. I have been struggling to raise my skills to higher levels so I can overcome this obstacle. The trouble is, the camera is just too inconsistent with its exposure performance—it is that simple. I now have taken thousands of shots with it. I know a bunch of you will jump down my back now, claiming it is my incompetence which generates the exposure problems, but there is nothing I can do for you. The fact is a camera of this cost should not underexpose to the degree it does---PERIOD!

I sometimes wonder if Corporate Pentax people hang out here and jump on anyone faulting the camera, accusing them of incompetence. Yes, this is a silly notion, but no sillier than the notion that all the underexposure issues with the K20 are from user incompetence. BTW, this is a very good post!

Regards,


Ernest



Humanity subdues inhumanity as water subdues fire.

Mencius 6A:18.
Post examples w/ EXIF data in tact (basically to determine metering method) and a better discussion can be made. Baseline metering is one thing, inconsistent metering is another.

06-14-2008, 09:17 PM   #39
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I find exposures and exposure consistency to be the best part of the K20D right now. Looking forward to those shots with EXIF. (No, i do not work for corporate Pentax....)
06-15-2008, 11:59 AM   #40
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jeffkrol
QuoteQuote:
Post examples w/ EXIF data in tact (basically to determine metering method) and a better discussion can be made. Baseline metering is one thing, inconsistent metering is another.
To post here I must drastically reduce file size with software. My experience doing this shows the EXIF data is corrupted afterwards. Any suggestions? Thanks.

Regards,

Ernest




"Humanity subdues inhumanity as water subdues fire."


Mencius 6A:18.
06-15-2008, 12:54 PM   #41
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QuoteOriginally posted by Jewelltrail Quote
jeffkrol

To post here I must drastically reduce file size with software. My experience doing this shows the EXIF data is corrupted afterwards. Any suggestions? Thanks.

Regards,

Ernest




"Humanity subdues inhumanity as water subdues fire."


Mencius 6A:18.
Well to start there are a bunch of free file transfer sites.
YouSendIt - Send large files - transfer delivery - FTP Replacement
Also do you have "web space" w/ your isp? That would work too.
At dp review if you wantto link to large files you add a semicolon at the end ;
Stops autoloading and people can retrieve the image by clicking on it.
But here you just add it as a link, not image..like so. Now all you need is somewhere to upload and park your image.
http://www.qualiteitems.com/images/metersense.jpg
06-15-2008, 01:51 PM   #42
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QuoteOriginally posted by stevebrot Quote
Wow!

Not only is there a left shift of the curve, but there is also a significant difference in contrast!
And why is this wow? Isn't the difference in color/contrast/detail/bokeh, the differences in how lenses draw what makes some lenses so desirable, while others never appeal much?

What i'd like to know is what kind of exposure do we get if the original 2 lenses are used in P, Av, Tv, TAv, Sv? Since i keep an eye on analog bars when using M, i'd wager that with either lens i'd get a similar exposure, with different color/contrast.
06-15-2008, 04:42 PM   #43
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QuoteOriginally posted by morfic Quote
And why is this wow? Isn't the difference in color/contrast/detail/bokeh, the differences in how lenses draw what makes some lenses so desirable, while others never appeal much?

What i'd like to know is what kind of exposure do we get if the original 2 lenses are used in P, Av, Tv, TAv, Sv? Since i keep an eye on analog bars when using M, i'd wager that with either lens i'd get a similar exposure, with different color/contrast.
I was not so surprised by the difference in contrast as I was by the left shift in the curve. (Thought the contrast difference was also pretty impressive...)
06-15-2008, 05:55 PM   #44
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Differences in color and contrast are definitely understandable but a 2/3 EV difference in exposure is a bit more than one would expect.
06-15-2008, 07:24 PM   #45
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QuoteQuote:
Well to start there are a bunch of free file transfer sites.
YouSendIt - Send large files - transfer delivery - FTP Replacement
Also do you have "web space" w/ your isp? That would work too.
At dp review if you wantto link to large files you add a semicolon at the end ;
Stops autoloading and people can retrieve the image by clicking on it.
But here you just add it as a link, not image..like so. Now all you need is somewhere to upload and park your image.
http://www.qualiteitems.com/images/metersense.jpg
jeffkrol

Thanks, this is a big help--also, this will help me in the future when I want to send full-sized files to family and friends. Only problem is I have never used one of these sites. It will take me some time to set this up and retrieve/post files. I have never posted at DPreview.


Regards,


Ernest

"Humanity subdues inhumanity as water subdues fire."

Mencius 6A:18.
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