How to find Pentax lense's sweet spot....

Started Feb 22, 2009 | Discussions thread
GaryDeM Veteran Member • Posts: 6,297
Re: How to find Pentax lense's sweet spot....

the mtf is part of the program line in the menu. it sets the way the program or auto modes work. there are 4 program lines. depending on the camera maker there could be more than the 4. the 4 are normal or default, the action, dof, and mtf. the normal line lets the camera settings climb in shutter speed to about a 1/60sec then the shutter speed and fstop climb equally as the light climbs. the action line is the same but after the the shutter reachs the 1/60sec the emphasis is on letting the shuttter speeed climb at the expense of the dof. the dof line is the nopposite of what was just said. the mtf is different. lenses perform their best in terms of image quality when the fstops are between f5.6 and f11.0. below and the lens is trying to let in all the light in it can at the expense of some performance. above f11.0 the lens is running into difffraction distorsion in ever increasing amounts. so in mtf line the lens is trying to keep the fstop in the given range for max IQ.

on the k20 and the *istD the matrix metering mode is a bulit in way of preventing highlight blowouts. what is happening is that the screen is made up of 16 segments upon metering the dslr sets the shutter speed and fstop for the whole image THEN checks each segment for any blowouting if a segment or segments are found it lowers the exposure so that that segemnt(s) are not blowing. this is a bulitin form of EC. it is not necessary for the user to use EC himself in matrix mode. the dslr is doing it for him. after i found out what the dslr (my *istD) was doing i leave the dslr in matrix mode and i have not had a highlight blowout in over 4 yrs. the matrix mode prevents it. the only thing that the user has to be aware of is the tendacy for the image taken in matrix mode to be somewhat dimmer than expected. to fix just use auto levels in the pp software. full normal brightness is restored and no blowouts at all.

i have read that many pentax dslr users have complained about underexpposed images. if they were using matrix mode the i mages are what they supposed to be, the user were simply unaware of how it works.

this is also a easy way of combining the matrix metering with program or auto shooting mode. you end up with a dslr that keeps the lens performing at it best and the matrix metering gives error free exposures with no blowouts.

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