Shooting manual lenses on Pentax DSLRs
One of the best things about shooting a modern Pentax DSLR is having access to 35 years worth of wonderful K mount lenses- all with shake reduction! That’s a feature no other camera manufacturer can claim. The problem is that using these lenses effectively on a DSLR is somewhat of a black art that requires the camera be set up properly. Read on for step-by-step instructions of how I set up my Pentax K10D DSLR for use with a manual lens.
Old K mount manual lens selection is a blog article all to itself. Rather than discuss the pros and cons of specific lenses, I’m merely going to group them into two major categories: “A” lenses and “M” lenses. A series K mount lenses (like the 50mm f/1.7 shown above) can be thought of as essentially manual focus lenses on a Pentax DSLR.
“A” series lenses have an “A” position on the aperture ring. Engaging this setting locks the aperture ring and allows the camera to control the aperture setting with one of the E-dials on the camera body. The camera can be shot in any mode (with the camera automatically adjusting the aperture setting as required) just like with a regular modern AF lens with the only difference being the requirement to manually focus the lens. Placing the aperture ring in any other setting than “A” essentially turns it into an “M” lens. More on that in a moment.
When using any manual focus lens you need to tell the camera what the focal length is of the lens being used to get the best SR performance. To do this, simply turn the camera off, mount the lens, make sure SR is ON, turn the camera back on, and select the focal length of the lens being used on the rear LCD when prompted. You can do this after the fact using the menu system, but the fact is you should always turn the camera off when changing lenses anyway and Pentax makes this process practically automatic (assuming you have the SR turned ON when you turn the camera back on). Another benefit of doing this is that the focal length you input here will be recorded in your shot EXIF data- making it easier to tell which lens you were using later.
If your manual lens is a zoom it seems there is some conjecture over what you should do. Ideally, you would input the focal length you are shooting at but that seems rather tedious. Most of the info I have read says you will get the best results by using the shortest focal length setting for your lens. I would agree with this but I also think that you should use the longest setting if you are shooting primarily at the long end of the zoom range. It only makes sense as the SR would need to move a lot more to compensate for the exaggerated movement of a long telephoto focal length than at a shorter one.
You won’t have to mess with the SR setting when you switch back to a modern AF lens as the lens will communicate with the camera and make the adjustment automatically. You will need to repeat this process anytime you mount a manual lens and/or cycle the power switch with a manual lens attached.
Logic would dictate that if you are shooting with a manual focus lens you should switch the camera into manual focus mode and this is the case most of the time. When shooting in MF with a manual lens you will still get focus confirmation when your subject is in focus via the center focus point illuminating red briefly in the viewfinder, the focus indicator lamp lighting (also in the viewfinder) and the audible focus lock beep (assuming it is enabled). See below:
From what I can tell, the camera will only use the center focus point with older manual lenses (A and M). You can select other focus points with modern AF lenses when in MF mode. I always use the center point, focus, recompose, then shoot anyway. But that’s just the way I roll. Dialing in accurate focus can be tricky as the range of movement of the manual focus lens’ focus mechanism and front/back focus issues can throw the focus sensor off. The focus indicator will often stay illuminated over several degrees of focus ring rotation (in-focus range). This can be especially frustrating when using fast lenses with extremely short depths of field while trying to achieve critical focus on a specific point of the subject. Trial and error with lots of high magnification LCD review is the best way to get it right. Each lens will likely have its own characteristics that will need to be learned. A good excuse to take lots of pictures :D Here’s an article covering MF technique.
Another focus technique with manual lenses is “catch-in-focus” or “focus trap.” With this technique you set the camera to AF-S mode, fully depress the shutter then manually dial in the focus. As soon as focus is achieved the shutter will release. Problem is that it will either fire at the beginning or at the end of the in-focus range (depending on which direction the focus ring is being rotated) and the actual desired focus point may be somewhere else within the in-focus range. Also, if you are shooting at the slow end of hand-holdable shutter speeds you can actually get what I’d call “focus blur” as you focus through the desired focus point while the shutter is open. I find the focus trap technique most useful when trying to catch action shots and/or when shooting at smaller apertures in bright light. I find it basically useless when shooting wide open and/or in low light.
Metering is another issue with manual lenses. With my A series lens the camera uses the metering mode selected on the dial (spot, center weighted or pattern). However, with my Takumar 135mm f/2.5 M series lens (pictured at the top of the page) the camera defaults to center weighted averaged metering despite the fact that the selector is set to pattern. The other thing is that the exposure does not lock when you achieve focus in MF mode like it normally does in AF mode (with any lens in MF). So, if you do like I do and focus, recompose then shoot, you will likely get a different exposure when you recompose then you did when you set the focus. In pattern metering mode with my A series lens I rarely find this to be a problem as the pattern metering seems pretty adept at figuring things out. However, I occasionally have to use the AE-L button in high contrast situations to get the desired exposure, especially with my M series lens. Spot metering is typically useless unless you use the AE-L function.
Another metering issue is a bit more complicated. It seems that the metering system in the modern Pentax DSLRs is not optimized for use with the older manual lenses. I have read a lot about this and still can’t quite explain what is going on. Bottom line is that you may need to adjust your exposure up or down depending on the combination of camera/lens/aperture/subject being used. When shooting my A series lens in Av mode (as I typically do) I generally dial in around +0.7 to +1.0 EV compensation at f/1.7. If I shoot at smaller apertures I can often back off this setting depending on the subject matter. However, I do pretty much the same thing with every lens I use on my K10D so this is an area where experimentation is definitely required (on a lens-by-lens basis).
At this point you have pretty much all the information needed to get started shooting with an older A series manual lens. However, there are still a number of things left to do before you can even take the first picture with an M series lens. After following the directions above for mounting the lens, inputting the focal length and changing the focus mode, you will likely be greeted with a locked up camera and the dreaded flashing “F – -” screen:
(Please excuse my cracked LCD cover. This camera gets a lot of use.)
Seems to me Pentax should have made this “F – - -” instead ;-) What this is telling you is that the camera can not control the aperture of the lens mounted. What you need to do is tell the camera that everything is OK and to let you have control of the situation. To do this you have to navigate to the Custom Function menu and change the “Using aperture ring” setting to “Permitted”:
I guess Pentax sets this to “Prohibited” by default to force newbies into researching the use of manual lenses on their DSLRs. Whatever. This is likely the single most asked question of first-time M series lens users on a Pentax DSLR. Do it once and you won’t have to change it again. While you are in the Custom Function menu, check and make sure that the “Green button in TAv & M” setting is at the default setting of “1″ (”Program Line”). More on this in a moment.
Now that you have done all of this, you should see something like this on your status display:
There’s still an “F – -” showing in the display but now it should be steady and not flashing and the rest of the controls (including the shutter) should now be operational. The “F – -” now only means that the camera doesn’t (and won’t) know what aperture setting the lens is set to. Now we are getting much closer to being ready to shoot. Before we do though, I need to cover another detail. And yes, you will get to shoot pictures eventually :D
There were two surprising things for me the first time I went through this process with my first M lens. I eagerly tore open the box from KEH, mounted up my lens, selected Manual exposure mode and proceeded to peer through the viewfinder the first time in preparation for taking my first shot. Right off the bat, I was surprised that the aperture did not close down when I rotated the ring on the lens like it used to on my old K1000. It makes sense, keep the viewfinder bright for focus and composing and stop the lens down only when the shutter releases. This brought me to my next conundrum: there is no active exposure meter display with an M lens. All I could see was a shutter speed and that damn F – -:
I was shocked. I thought for sure I’d have a nice little exposure bar graph in the viewfinder with which to dial in the exposure just like I do with my AF and A series lenses in Manual exposure mode. Of course, I realize now that if the camera is holding the aperture wide open all of the time, and it has no way of knowing what the chosen aperture setting on the lens is, it has no way of calculating the given exposure. Duh! After fiddling blindly with the shutter speed and aperture ring and getting a few horribly mis-exposed shots I knew there had to be a better way- either that or my old Tak didn’t work with my K10D. So, I got on the internet and did a little searching. That’s when I learned about “stop down metering” and the purpose of that little green button when shooting in manual mode.
Here’s how it works. In Manual exposure mode, you select your desired aperture using the ring on the lens, the desired ISO via the LCD, focus, compose, and press the green button. The camera will then briefly release the aperture so that it closes down to the desired setting (read: “stop down”) and take a meter reading. It will then offer up a shutter speed that represents a neutral exposure reading for the scene. At this point you can simply take a shot, review the results and adjust the shutter speed up or down to achieve the desired exposure for the scene. You will have to repeat this process for each new composition until you get to the point that you can just calculate the desired exposure by eye- like we used to do with old manual film cameras ;-)
This use of the Green button for stop-down metering seems to be the preferred method for most Pentax DSLR owners using manual lenses. As is often the case with these sorts of things, there are other ways. For instance, by holding the optical Depth of Field preview function closed (the icon to the right of the ON label on the power switch shown in the photo above), you can manually stop down the lens. The camera will then display the traditional bar graph exposure meter for you to adjust exposure with like with an old K1000. While this works, I find it rather awkward to use as my shutter speed control has been re-mapped to the front E-Dial wheel. YMMV.
My preferred method for shooting my M series Takumar 135mm f/2.5 is to shoot in Aperture priority mode (Av). The metering functions just like it would with any other MF lens and I can use EV compensation like I normally would. The main potential drawback is that the lens is always shot wide open- despite what the setting on the aperture ring may be. For me this is less of an issue as I typically like to shoot wide open anyway. If I need to stop down for some reason I typically resort to the DoF preview method as I like to see the exposure meeter. It correlates better with what I am used to seeing through the viewfinder when I shoot my other lenses.
This is by no means a complete tutorial on using manual lenses on Pentax DSLRs. There are a number of nuances for different lens and camera combinations and countless permutations of old lenses, each with its own idiosyncorosies. I offer up this “guide” as merely an informational starting point to help clear up some of the mystery for anyone looking to give an old manual lens a try. Here is another excellent step-by-step guide for shooting manual lenses on Pentax DSLRs. Be sure to research your specific lens/camera combination for more detailed specifics. Be aware that there are some K mount lens variations that do not work with modern DSLRs for a number of reasons. Do your research! That being said, many older K mount lenses represent terrific values and often will outperform their modern counterparts. This is one area where “they don’t make them like they used to” can really be true!
Several people have asked so I added this shot of my “studio” set-up I used to take the pictures in this blog post. I used a Panasonic Lumix FX07 pocket camera with a custom WB setting and + 7/10 EV exposure compensation. Framing up tight in macro mode helps keep the kitchen out of most of the shots. While most of my studio shots thus far have actually been shot in a small studio I have access to at school, it’s often easier to just do this little kitchen set-up at the house. I’ve been doing this enough that I’m contemplating mounting a small retractable white vinyl window shade to the bottom of the cabinet for an instant pull-down seamless backdrop. That is if the wife will allow it ;-)