On Friday 05 July 2002 06:01 am, David A. Mann wrote: > Hi all, > > Yesterday I got my slides back from the 400mm test I did, comparing > my Tokina SL 400/5.6 with my long-sought-after Pentax FA*400mm f/5.6. > > I've only just found time to go over the slides in detail. My > impressions follow :) I performed the "test" with a Z-1p on a tripod > (Manfrotto 055 with 029 head), both lenses manually focussed using > the body's focus indicator. I rested my hand on the lens to damp > vibration. > > I don't remember if I set the FA aperture manually or by using the > dial on the body (more about this below). Film was Fuji Provia 100F, > slides examined under a cheapish 10x loupe (Horizon brand). I might > look for a 10x (or greater) loupe with better contrast as this one > isn't too great. An SMC 20x would be nice :) Exposure was metered > off the grass and was set manually. > > My test-bed is a building at a nearby high school. Its an old brick > building which you can see a picture of at: > http://www.digistar.com/~dmann/temp/cbhs_small.jpg > There's a sports field in front of this building so I can get way > back for testing longer lenses. There's heaps of detail in there, > and I can check out low- and high-contrast sharpness/detail, > distortion, colour fringing and contrast all at once. > > My scanner is not too great at 35mm film so you'll have to read my > comments instead. > > At f/5.6 both lenses are soft. I think the Pentax has a slight edge, > but this looks like its due to higher contrast. Or its due to the > amount I paid for it relative to the Tokina. I want it to be sharper > :) > > At f/8 the Pentax improves a bit but is still a bit on the soft side. > Still a little better than the Tokina. > > At f/11 the picture completely changes. The Pentax becomes very > sharp while the Tokina doesn't change by much. I am at a loss to > explain why the Z-1p picks f/8 in MTF mode. F/11 is obviously the > "sweet spot" (unless my focus was slightly out). I've always had > strange "optimum" numbers out of that mode, so I'll just take them > with a grain of salt. > > The Tokina lens remains about the same right down to its smallest > aperture; f/22. In fact I was surprised by just how soft it looked > as I've had some pretty decent 6x8 prints from this lens handheld at > f/8. > > The Pentax lens retains its sharpness until f/32 where it softens > slightly. F/45 is a little softer than f/32. I presume this is due > to diffraction. It ends up looking pretty similar to f/8. The slow > shutter speed may have had an effect as well. At f/45 I would have > had a shutter speed around 1/8th or 1/4, which is just asking for > trouble. > > These photos were all taken near-infinity, BTW. I haven't done a lot > of closeups yet. The Pentax lens focusses down to 2m which is a > feature that really attracted me to it. The Tokina only goes to 4m > and I find I need an extension tube for tame "wild"-life... but that > screws up infinity :) > > One thing that really bugged me is that the Tokina and Pentax not > only have different colour renditions (Tokina is a bit warmer), but > there was a noticeable difference in exposure between the two lenses. > I'd hazard a guess of 1/3 stop or so. This is what makes me wonder > how I set the aperture of the Pentax lens; the auto-aperture setting > is known to be slightly inaccurate at times. Maybe the Pentax also > transmits a little more light due to SMC? My earlier comparison of > the 15mm Pentax-A vs 17mm Tokina SL was done on print film so I > wouldn't have noticed anything there. > > I found that the Pentax tripod shoe is infinitely superior to the > Tokina. Pentax's is quite substantially constructed and the foot > cannot be removed. You can rotate the lens around it, and it > "clicks" every 90 degrees. The Tokina has a small removable foot > which is attached with little knurled thumb-screws to the ring, which > doesn't "click" as you rotate. These screws come loose no matter how > hard you tighten them, which really frustrates me when using it on a > ballhead & monopod. I am tempted to put some shake-proof washers > under them. > > The Pentax shoe is located a bit further forward and is a bit taller > than the Tokina. This made a world of difference. With the Tokina > lens on the tripod, I could not detach or mount the body without > removing the grip strap (or releasing the lens with my third hand). > The plastic "base" of the grip strap interfered with the tripod head. > With the Pentax lens, I had no problem at all. > > Another distinct advantage of the Pentax lens is that it has auto > focus. Thats the other reason I bought it :) I will need to > practice my follow- focus because I had a lot of trouble keeping > flying gulls in the AF sensor. I'll have to get some Provia 400F for > the handheld stuff. > > Manual focus is smooth and there is not much resistance so I can > easily focus it with just a finger or two. This is good, IMO, as its > easy & accurate and doesn't shift unless you tell it to. It also > means I can support the lens with my hand toward the end of the > barrel, and focus with my two smaller fingers. Anyone who goes to > the Duxford airshow should try out Cotty's 300mm f/2.8 lens. Its an > absolute dream to focus. Just don't drop it, or he'll do to you what > he did to his cable release when I was there ;) Don't worry Cotty, I > bet Ansel Adams himself broke a few. > > I found the MF/AF clutch really handy. I found that the Z-1p > occasionally has a bit of trouble locking focus, and it can really > help if I pre-focus. Or it might lock onto something in the > background when you're trying to do a closeup (things go _very_ out > of focus at 400mm). Prefocussing is really quick & easy with the > clutch. Its smooth and easy to operate, but this is a bit of a pain > when carrying the lens around (I tend to hold it by the focus ring as > thats where it balances best). It will sometimes "click" back & > forth if I swing the rig too hard. No big deal, if it were any > stiffer I'd complain louder. When set to AF, the focus ring can > still turn a bit, but it will then "lock" into place where it can't > be moved unless set to MF. This is different from the FA*24/2.0 > where the focus ring can still be rotated if AF mode (but you feel > click- stops). > > One thing I really would have liked is a focus limiter switch > (especially with an adjustable limit). Note to Pentax engineers: > when you design the 400mm f/4.0, put a focus limiter in. Yes, I want > a 400mm f/4.0 and I don't want Canon's one :) > > The following day was _very_ dull and I took a few photos of ducks, > provided they would sit still for long enough. With the 100ASA film > I could only manage 1/30th at f/5.6 at best, so I ended up with some > pretty soft pictures despite using tripod and mirror prefire. I > think the lens might have been shivering in the cold; I certainly > was! I got a nice "macro" of a leaf with some incredible detail; I > think I shot that one at f/16 for some absurd shutter speed (1/2s?). > > After I finished that roll I loaded some Kodak Supra 400 and twisted > the ISO right up to 1600. And I still couldn't get handholdable > shutter speeds... :( I can't wait for summer. > > I haven't finished the Supra yet. I expect it to look horrible at > 1600 but I don't mind too > much. Occasionally I like to shoot a roll of Superia 800 at 3200ASA, > just for effect. > Any further underexposed and the lab's machine won't print it :) > > From what I've seen of the bokeh of this lens, it looks pretty nice. > I did not do a flare > test. I wasn't prepared to put the sun in the frame. I have noticed > a loss in contrast when the sun gets past the hood, though. > > Thats all for now :) > > Cheers, > > > - Dave > > http://www.digistar.com/~dmann/ (out of date) > - > This message is from the Pentax-Discuss Mail List. To unsubscribe, > go to http://www.pdml.net and follow the directions. Don't forget to > visit the Pentax Users' Gallery at http://pug.komkon.org .
-- Kenneth Archer, San Antonio, Texas [EMAIL PROTECTED] - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
