[ZombieArmy]

I have mixed feelings about focus peaking. It works well for shallow or moderate focus gradients and sucks if the gradients are steep with huge areas (sometimes a meter deep) showing the same "peak". Still though, the proof of the pudding is in the eating and if it works for you and others, that is good enough for me.


Steve

For me the wire frame peaking helps a lot with that. Though to be fair that can only be used in daylight.

Does "focus peaking" take into consideration the aperture/depth of field?

[stevebrot]

Does "focus peaking" take into consideration the aperture/depth of field?

My understanding is that it is basically done using a method similar to contrast detect auto focus (CDAF) with areas interpreted as "in-focus" edge receiving a highlight color. So, yes, DOF affects performance in the same manner as it affects CDAF.

Steve

[bdery]

My understanding is that it is basically done using a method similar to contrast detect auto focus (CDAF) with areas interpreted as "in-focus" edge receiving a highlight color. So, yes, DOF affects performance in the same manner as it affects CDAF.

It's almost assuredly done via a Fourier Transform, which is a mathematical tool which transforms wavelength information into frequency information. Or in other words, it can be used to find edges with a sharp definition. Then the display highlights spots where the transitions are ''sharper''. Since the measurement is made with the lens wide open, it lets the user nail focus on the narrowest DOF possible. When the aperture closes, the DOF increases, while still being centered on the same spot.

[stevebrot]

It's almost assuredly done via a Fourier Transform, which is a mathematical tool which transforms wavelength information into frequency information. Or in other words, it can be used to find edges with a sharp definition. Then the display highlights spots where the transitions are ''sharper''. Since the measurement is made with the lens wide open, it lets the user nail focus on the narrowest DOF possible. When the aperture closes, the DOF increases, while still being centered on the same spot.

Thanks for the detailed explanation. Where things get tricky and perhaps what the earlier comment was referring to is the tendency of live view on Pentax dSLRs to operate stopped down to as narrow as about f/5.6 under even moderately bright conditions. For example, it is a dim rainy morning outside (~LV 10) and I just did a small focus peaking test using my K-3 with FA 35/2.0 and with a day-lit window sill and a few other items as subjects. The indicated exposure was 1/160s for f/2.0 at ISO 100. Despite the fairly dim conditions, live view had the lens stopped down for viewing to about f/5.6. Focus peaking showed a range of "in-focus" edges spanning about 25cm depth at a 45° angle and 70cm distance. Assuming a taking aperture of f/2.0, missed focus is almost assured.

Switching to aperture ring control with the same lens and the span of "in-focus" edges shrank to about 7cm depth. While still not adequate for fine focus, this second view is more useful than the first.

Going back to camera control of aperture, I switched to magnified live view and the camera obliged by opening back up to maximum aperture, allowing much better application of focus peaking, though it still picked up "edges" a full centimeter apart in depth.

To be clear, this was done at an angle, which is problematic for most focus systems. Behavior with a flat target is much different. That being said, using my peepers and surface detail (time to paint the window sill?) performed better for fine focus this dim morning than focus peaking.


Steve

[bdery]

Thanks for the detailed explanation. Where things get tricky and perhaps what the earlier comment was referring to is the tendency of live view on Pentax dSLRs to operate stopped down to as narrow as about f/5.6 under even moderately bright conditions. For example, it is a dim rainy morning outside (~LV 10) and I just did a small focus peaking test using my K-3 with FA 35/2.0 and with a day-lit window sill and a few other items as subjects. The indicated exposure was 1/160s for f/2.0 at ISO 100. Despite the fairly dim conditions, live view had the lens stopped down for viewing to about f/5.6. Focus peaking showed a range of "in-focus" edges spanning about 25cm depth at a 45° angle and 70cm distance. Assuming a taking aperture of f/2.0, missed focus is almost assured.

Switching to aperture ring control with the same lens and the span of "in-focus" edges shrank to about 7cm depth. While still not adequate for fine focus, this second view is more useful than the first.

Going back to camera control of aperture, I switched to magnified live view and the camera obliged by opening back up to maximum aperture, allowing much better application of focus peaking, though it still picked up "edges" a full centimeter apart in depth.

To be clear, this was done at an angle, which is problematic for most focus systems. Behavior with a flat target is much different. That being said, using my peepers and surface detail (time to paint the window sill?) performed better for fine focus this dim morning than focus peaking.

I'll have to test this to understand better, because I never noticed the camera toying with the aperture in live view. I would have assumed that the aperture change could be heard, but it seems that's wrong.

[gump]

Not meaning to interrupt the tangent from my original question BUT the 50mm 1.8 shipped today. I plan to do some comparisons with the 18-55 kit and see if all the experts know what they are talking about.

[stevebrot]

I plan to do some comparisons with the 18-55 kit and see if all the experts know what they are talking about.

Prepare to be amazed.


Steve

[Gary H Perth]

Prepare to be amazed.


Steve

All this talk makes me want to get one - and I already have two 40mm, three 50mm, one 55mm and a macro 50mm.

This is not even my favourite focal length, I would probably go for the DA70mm Limited for portraits, or use the amazingly sharp Pentax-F 35-70mm.

[Bertrand3000]

All this talk makes me want to get one

Then what are you waiting for?

I already have two 40mm, three 50mm, one 55mm and a macro 50mm.

... Oh. You seems to suffer from LBA. I'm sure you feel you need that lens, but you should talk with us first.

[stevebrot]

All this talk makes me want to get one

The aspect that amazes is that the optical quality is top shelf, despite the low cost. I am very fond of mine, mostly because it is extremely light and fun to shoot with. That said, I have better fast 50s that I generally prefer.


Steve

[pschlute]

Originally posted by Gary H Perth Quote
I already have two 40mm, three 50mm, one 55mm and a macro 50mm.
... Oh. You seems to suffer from LBA. .

A very mild dose

[bilybianca]

For some time I had the A 50mm f1.4, the F 50mm 1.4 and the FA 50mm f1.4 (still have the two latter). When I did some comparison test shooting I couldn't see any difference between them (all excellent lenses) except that the FA rendered a bit warmer colours. I'm not sure wether it actually was the lenses, or if the camera for some reason changed the white balance (auto WB, but I do think it was the lenses). Maybe different coatings between F and FA? No matter what people mutters about them being obsolete and of an old optic design, I think they are very usable.

Kjell

[Archimedes the Dog]

The aspect that amazes is that the optical quality is top shelf, despite the low cost. I am very fond of mine, mostly because it is extremely light and fun to shoot with. That said, I have better fast 50s that I generally prefer.


Steve

I sold mine when I got the DA* 55 1.4, and I miss it at times. I took some photos I am proud of with the 1.8.