K10D metering: different lenses

**Lowell Goudge** · 02-02-2009, 06:45 AM

Originally posted by fgpinarli

Hi. My K20 D underexpose with M 100mm macro and K 135/2.5 with wider exposure, f:4 and f:2.5 respectively. When I stop down the lenses, the exposure become correct without compensation. I use them im M mode metering with the green button. Related the use of the central part of the lenses? Any explanation? Thank you

try this

https://www.pentaxforums.com/forums/241716-post69.html

it has been well documented, i think you will find it will also over expose beyond F5.6

the bottom line, and I made this point in an earlier post, as have about 6 other people, is that you need to check how your equipment performs.

It is not all that hard, even if you have a ton of lenses.

kevbirder · 02-09-2009, 03:56 PM

Yes I know in practice we have to know our equipment and adjust for its failings.

However I am astounded that when we buy an expensive modern piece of computerised equipment with multiple light metering options that we should have to accept that this equipment cannot apparently do simple calculations like double the exposure for each stop adjustment away from full aperture.

Non-linear screen responses are cited as responsible, but if true, can this not be programmed in to the calculation?

It just seems amazing to me that you can have muli-segment, center weighted or spot metering and then at the end of the day you have to manually assess and correct the result, or even worse, always make the same correction that the camera is unable to do for itself.

**Lowell Goudge** · 02-09-2009, 05:15 PM

Originally posted by kevbirder

Yes I know in practice we have to know our equipment and adjust for its failings.

However I am astounded that when we buy an expensive modern piece of computerised equipment with multiple light metering options that we should have to accept that this equipment cannot apparently do simple calculations like double the exposure for each stop adjustment away from full aperture.

Non-linear screen responses are cited as responsible, but if true, can this not be programmed in to the calculation?

it is, and this is why A series lenses meter much better than earlier ones,

Quote:

It just seems amazing to me that you can have muli-segment, center weighted or spot metering and then at the end of the day you have to manually assess and correct the result, or even worse, always make the same correction that the camera is unable to do for itself.

the issue is people want all things, better brighter view finders easier to see throug, which causes them to make viewing screens that have more depth of field than the images the lens gives, and makes them brighter with the lower cost slower lenses. Remember, most kit lenses and low cost zooms are F4-5.6, where as in the bad old days of film, even the cheapest kit 50 was F2.0

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02-02-2009, 06:45 AM	#16
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	Originally posted by fgpinarli Hi. My K20 D underexpose with M 100mm macro and K 135/2.5 with wider exposure, f:4 and f:2.5 respectively. When I stop down the lenses, the exposure become correct without compensation. I use them im M mode metering with the green button. Related the use of the central part of the lenses? Any explanation? Thank you try this https://www.pentaxforums.com/forums/241716-post69.html it has been well documented, i think you will find it will also over expose beyond F5.6 the bottom line, and I made this point in an earlier post, as have about 6 other people, is that you need to check how your equipment performs. It is not all that hard, even if you have a ton of lenses.

02-09-2009, 03:56 PM	#17
kevbirder Junior Member Join Date: Nov 2008 Location: Taunton, UK Posts: 48	Yes I know in practice we have to know our equipment and adjust for its failings. However I am astounded that when we buy an expensive modern piece of computerised equipment with multiple light metering options that we should have to accept that this equipment cannot apparently do simple calculations like double the exposure for each stop adjustment away from full aperture. Non-linear screen responses are cited as responsible, but if true, can this not be programmed in to the calculation? It just seems amazing to me that you can have muli-segment, center weighted or spot metering and then at the end of the day you have to manually assess and correct the result, or even worse, always make the same correction that the camera is unable to do for itself.

02-09-2009, 05:15 PM	#18
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	Originally posted by kevbirder Yes I know in practice we have to know our equipment and adjust for its failings. However I am astounded that when we buy an expensive modern piece of computerised equipment with multiple light metering options that we should have to accept that this equipment cannot apparently do simple calculations like double the exposure for each stop adjustment away from full aperture. Non-linear screen responses are cited as responsible, but if true, can this not be programmed in to the calculation? it is, and this is why A series lenses meter much better than earlier ones, Quote: It just seems amazing to me that you can have muli-segment, center weighted or spot metering and then at the end of the day you have to manually assess and correct the result, or even worse, always make the same correction that the camera is unable to do for itself. the issue is people want all things, better brighter view finders easier to see throug, which causes them to make viewing screens that have more depth of field than the images the lens gives, and makes them brighter with the lower cost slower lenses. Remember, most kit lenses and low cost zooms are F4-5.6, where as in the bad old days of film, even the cheapest kit 50 was F2.0