MightyMike
Forum Pro
I informed the forum a couple months ago about a systemic issue regarding continuous focus and flawed images. Initially i got backlash as i was using a 3rd party lens but I subsequently proved the point with a Pentax lens. In those posts I also got reports of other brands with the same issue.
The issue is that in order to obtain focus tracking and burst rate the focus motor doesn't stop between photos and therefore is moving during the exposure. When this happens and the effect becomes visible most people would pass it off as missed focus, FF or BF while maybe scratching their heads wondering if it actually was. This problem isn't solved by switching to a slower burst rate as the lens still doesn't stop for the exposure. The problem will be more visible with sharper higher quality lenses and higher resolution sensors as well when doing photography that involves fast lens movement. The best place to see it would be action on a field sport where you have a fast shutter speed and you can see the range of DOF, you know the subject is in focus but the subject and the grass on the field while still in focus doesn't look sharp, I call it mushy. You know the lens is better, you know SR is turned off, you know your shutter speed is fast and even if the subject has a little motion blur the grass does not and should not at such a shutter speed but its still mushy.
Anyhow the solution to this issue, some on the forum came up with years ago was to use AF-S which stops the lens before each shot. Initially i thought that was silly but i wasn't thinking of it in the right way. I was thinking half press and when the lens stops focusing then full press, that is what comes naturally, however the method correctly done is to full press and when the camera takes a photo lift the finger and full press again. This alleviates any delay between focus confirmation and the shot being taken. To prove this method to myself i did it manually at the last airshow, and of the 691 photos i took before it got rained out I only deleted 246... 246?!?!? What?? that's a lot... Hear me out, almost all the 246 photos that were deleted were because the shutter speed was too slow, my attempt to get prop blur while the planes were doing aerobatics. You see if the shutter speed is too fast it looks like the prop is stopped and I've had photographers and wannabe photographers tell me that i didn't do it right all the while completely ignoring the fact that the plane was flipping around on all axis making it impossible to get a sharp photo at a prop blur shutter speed. But i digress... So I had just a few photos end up completely out of focus and that was a result of my timing and confusing the camera as to what i wanted it to do, but all other photos were in focus and were sharp, not one mushy photo like i used to get with AF-C.
There are drawbacks to this method, you do and can and will miss photos, your burst rate is rather slow, even slower when there is significant subject movement or low contrast and your finger will get tired.
So i spent the last couple months acquiring what is necessary to automate the process and even though i got a number of set-backs I've finally got a small ghetto fabulous device that will pulse the IR triggering command to the camera at a steady pace allowing for Continuous-AF-S. Initially I wanted to do this with a wired remote but the issues were the rubber cover over the wired remote jack would likely break off with regular use, it would be uncomfortable and there is no feedback from the camera that it has taken a picture to use to tell the camera to re-focus. I suppose feedback could be done through the hotshoe if you could convince the camera has an HSS flash on and you intercept the trigger command. Anyhow plan B was to use the IR system, when you set the camera in AF-S and IR triggering the camera will focus until the lens stops and then take a photo, it will ignore all other IR commands until its ready again, this way you just pulse the signal and let the camera do its thing. I wired up a 555 timer circuit with a power source, a relay, a switch and a cheap Chinese IR remote, I disconnected the IR LED and extended it out so it can be taped to the front IR panel of the camera. Switch it on and the camera will take photos at relatively regular intervals if in MF mode, and lessor intervals if it has to AF between shots.
Sounds great right, I was even considering to wire it to use a momentary switch so it wouldn't trigger when you didn't want it to. However there is a problem with the implementation of the IR system in the Pentax camera, at best with the camera set to MF and the trigger going between 5-10 times a second the fastest the camera will trigger is 1.8fps. By recording the IR remote we found there is no delay in the remote systems recycle time, that LED blinks off just as fast as you could want, its the camera that isn't programmed to receive a signal that often and therefore at best you'll get about the same burst rate as if you where triggering it manually with your finger, which is still better than nothing but not ideal. Still you might not get anything faster as the lens has to refocus with every shot and that delays shooting a fair bit.
I will attempt to use the device and report back on the feasibility of it and the feasibility of making it in larger quantities to sell however i have my doubts that it would be a widely accepted device. Despite that I'm sure it would benefit a number of us who do shoot action. Regardless of all the drawbacks I now fully endorse not using AF-C when it can be avoided and especially if you're getting random annoying mushy results that you shouldn't get. I will still use AF-C in situations where catching the moment is more important than avoiding a few mushy photos in each sequence.
I hope this helps people
The issue is that in order to obtain focus tracking and burst rate the focus motor doesn't stop between photos and therefore is moving during the exposure. When this happens and the effect becomes visible most people would pass it off as missed focus, FF or BF while maybe scratching their heads wondering if it actually was. This problem isn't solved by switching to a slower burst rate as the lens still doesn't stop for the exposure. The problem will be more visible with sharper higher quality lenses and higher resolution sensors as well when doing photography that involves fast lens movement. The best place to see it would be action on a field sport where you have a fast shutter speed and you can see the range of DOF, you know the subject is in focus but the subject and the grass on the field while still in focus doesn't look sharp, I call it mushy. You know the lens is better, you know SR is turned off, you know your shutter speed is fast and even if the subject has a little motion blur the grass does not and should not at such a shutter speed but its still mushy.
Anyhow the solution to this issue, some on the forum came up with years ago was to use AF-S which stops the lens before each shot. Initially i thought that was silly but i wasn't thinking of it in the right way. I was thinking half press and when the lens stops focusing then full press, that is what comes naturally, however the method correctly done is to full press and when the camera takes a photo lift the finger and full press again. This alleviates any delay between focus confirmation and the shot being taken. To prove this method to myself i did it manually at the last airshow, and of the 691 photos i took before it got rained out I only deleted 246... 246?!?!? What?? that's a lot... Hear me out, almost all the 246 photos that were deleted were because the shutter speed was too slow, my attempt to get prop blur while the planes were doing aerobatics. You see if the shutter speed is too fast it looks like the prop is stopped and I've had photographers and wannabe photographers tell me that i didn't do it right all the while completely ignoring the fact that the plane was flipping around on all axis making it impossible to get a sharp photo at a prop blur shutter speed. But i digress... So I had just a few photos end up completely out of focus and that was a result of my timing and confusing the camera as to what i wanted it to do, but all other photos were in focus and were sharp, not one mushy photo like i used to get with AF-C.
There are drawbacks to this method, you do and can and will miss photos, your burst rate is rather slow, even slower when there is significant subject movement or low contrast and your finger will get tired.
So i spent the last couple months acquiring what is necessary to automate the process and even though i got a number of set-backs I've finally got a small ghetto fabulous device that will pulse the IR triggering command to the camera at a steady pace allowing for Continuous-AF-S. Initially I wanted to do this with a wired remote but the issues were the rubber cover over the wired remote jack would likely break off with regular use, it would be uncomfortable and there is no feedback from the camera that it has taken a picture to use to tell the camera to re-focus. I suppose feedback could be done through the hotshoe if you could convince the camera has an HSS flash on and you intercept the trigger command. Anyhow plan B was to use the IR system, when you set the camera in AF-S and IR triggering the camera will focus until the lens stops and then take a photo, it will ignore all other IR commands until its ready again, this way you just pulse the signal and let the camera do its thing. I wired up a 555 timer circuit with a power source, a relay, a switch and a cheap Chinese IR remote, I disconnected the IR LED and extended it out so it can be taped to the front IR panel of the camera. Switch it on and the camera will take photos at relatively regular intervals if in MF mode, and lessor intervals if it has to AF between shots.
Sounds great right, I was even considering to wire it to use a momentary switch so it wouldn't trigger when you didn't want it to. However there is a problem with the implementation of the IR system in the Pentax camera, at best with the camera set to MF and the trigger going between 5-10 times a second the fastest the camera will trigger is 1.8fps. By recording the IR remote we found there is no delay in the remote systems recycle time, that LED blinks off just as fast as you could want, its the camera that isn't programmed to receive a signal that often and therefore at best you'll get about the same burst rate as if you where triggering it manually with your finger, which is still better than nothing but not ideal. Still you might not get anything faster as the lens has to refocus with every shot and that delays shooting a fair bit.
I will attempt to use the device and report back on the feasibility of it and the feasibility of making it in larger quantities to sell however i have my doubts that it would be a widely accepted device. Despite that I'm sure it would benefit a number of us who do shoot action. Regardless of all the drawbacks I now fully endorse not using AF-C when it can be avoided and especially if you're getting random annoying mushy results that you shouldn't get. I will still use AF-C in situations where catching the moment is more important than avoiding a few mushy photos in each sequence.
I hope this helps people
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