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01-11-2010, 06:34 PM   #16
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QuoteOriginally posted by Rusty Rat Quote
Why not have a more open mind and not automatically assume that is operator error.
You can post some shots and show us what's going on.

01-11-2010, 07:51 PM   #17
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QuoteOriginally posted by asdf Quote
You can post some shots and show us what's going on.
I asked, he threw them away

QuoteOriginally posted by Rusty Rat Quote
Why not have a more open mind and not automatically assume that is operator error.
its not a question of a closed mind, and I have not assumed the operator is at fault, but also possibly what the camera is doing.

without images we are blind,

I for one never throw anything away. I keep all my shots because they serve as constant reminders of what I do wrong every day, and I can also use the images to experiment with.
01-11-2010, 07:56 PM   #18
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QuoteOriginally posted by Rusty Rat Quote
Why not have a more open mind and not automatically assume that is operator error.
I don't think there was any assumption of operator error. You're a new member, people don't know you yet and asking for pictures or asking other (seemingly irrelevant to you) questions is standard practice. People are only trying to help.
01-11-2010, 08:01 PM   #19
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QuoteOriginally posted by Rusty Rat Quote
I'm aware that the screen doesn't allow the precise focus of a split image. My film experience with "real" cameras goes back to 1969 so I'm not a rookie at this.
Perhaps not, but the specific issue with modern micro-prism based focus screens that makes MF difficult at apertures beyond f/2.8 is a very new phenomenon. I'm guessing that's your problem right there - your "DA" lenses don't have large enough maximum aperture to really expose the problem inherent in modern focus screens, whereas your "A". That's also why the problem went away when using flash on tripod - you stopped shooting wide open, which made MF easy again.

It's MF at apertures larger than f/2.8 that is problematic on modern focus screens, because unlike the screens you've been using for the last 40 years, modern screens will show too much DOF. Thus there will always be more in focus in the viewfinder than in the picture. The trick is learning to anticipate this and account for it.

01-12-2010, 05:26 AM   #20
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QuoteOriginally posted by Marc Sabatella Quote
Perhaps not, but the specific issue with modern micro-prism based focus screens that makes MF difficult at apertures beyond f/2.8 is a very new phenomenon. I'm guessing that's your problem right there - your "DA" lenses don't have large enough maximum aperture to really expose the problem inherent in modern focus screens, whereas your "A". That's also why the problem went away when using flash on tripod - you stopped shooting wide open, which made MF easy again.

It's MF at apertures larger than f/2.8 that is problematic on modern focus screens, because unlike the screens you've been using for the last 40 years, modern screens will show too much DOF. Thus there will always be more in focus in the viewfinder than in the picture. The trick is learning to anticipate this and account for it.
marc

good point but I discounted this by the comment the OP made that A series lenses were OK on the tripod. If he can focus them on a tripod, then I keep coming back to camera settings and modes being used when hand held VS the DA's
01-13-2010, 03:12 PM   #21
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QuoteOriginally posted by Marc Sabatella Quote
Perhaps not, but the specific issue with modern micro-prism based focus screens that makes MF difficult at apertures beyond f/2.8 is a very new phenomenon. I'm guessing that's your problem right there - your "DA" lenses don't have large enough maximum aperture to really expose the problem inherent in modern focus screens, whereas your "A". That's also why the problem went away when using flash on tripod - you stopped shooting wide open, which made MF easy again.

It's MF at apertures larger than f/2.8 that is problematic on modern focus screens, because unlike the screens you've been using for the last 40 years, modern screens will show too much DOF. Thus there will always be more in focus in the viewfinder than in the picture. The trick is learning to anticipate this and account for it.
Than you Marc, that makes sense. All of the lenses I was using were 2.8s, however, when I ran some further tests after my original batch, I noticed enough randomness in the results to tell me something else was going on. I had initially compared shots taken with an SMC-A 28mm f2.8 to other shots taken with DA* f2.8 lenses (most in the f5.6 - f8 sweet spot of the lens). The 28 looked so bad that I thought I had a skunky lens. It was only when I used it on a tripod with flash did the results match what I had expected. A couple of my other SMC lenses didn't exactly "glow" when hand held. Since the image stabilization uses a manual entry of the focal length with MF lenses, that tells me extra software is involved in the process. As an IT guy, it's my first instinct to suspect software (I work with Microsoft products, enuff said).

My ground glass experience ranges from 35mm to 4X5 so I'm quite confident I know how to focus a lens. However, if the focusing screen doesn't return a result that I expect, then all bets are off.

Options for replacement screens?
01-13-2010, 04:19 PM   #22
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QuoteOriginally posted by Rusty Rat Quote
Than you Marc, that makes sense. All of the lenses I was using were 2.8s, however, when I ran some further tests after my original batch, I noticed enough randomness in the results to tell me something else was going on. I had initially compared shots taken with an SMC-A 28mm f2.8 to other shots taken with DA* f2.8 lenses (most in the f5.6 - f8 sweet spot of the lens). The 28 looked so bad that I thought I had a skunky lens. It was only when I used it on a tripod with flash did the results match what I had expected. A couple of my other SMC lenses didn't exactly "glow" when hand held. Since the image stabilization uses a manual entry of the focal length with MF lenses, that tells me extra software is involved in the process. As an IT guy, it's my first instinct to suspect software (I work with Microsoft products, enuff said).

My ground glass experience ranges from 35mm to 4X5 so I'm quite confident I know how to focus a lens. However, if the focusing screen doesn't return a result that I expect, then all bets are off.

Options for replacement screens?
I have a jinfinance split screen in my K10D which works very well, although some others I believe had had to put shim's to make focus adjustment.

The "gold standard" for split screens is Katzeye, but they are over $100 as opposed to $30. As I was unsure whether I wanted to use a split image finder, I went for the lowest cost option as an experiment and have been happy with it. Note however, being a split image, it will darken on one side or the other (function of viewing angle on the finder) and also interfere with spot metering.

In going back through your posts, I have some questions with respect to focusing.

- What were you using as indication of focus, the red spot or the green hexagon. Many people confuse the red spot (which shows the focus detector that is active) as indication of being in focus, it is not, the green hexagon indicates focus.
- have you tried manual focus with the DA lenses? if you have a DA lens at F2.8 it shoud be just as hard as the KA lenses at F2.8 and the same focal length,
- an observation about focal length, I have found that good focus on wide angle lenses is difficult at best because the depth of field is so good, you can easily make mistakes. In this respect the split image is a much bigger help with accurace focus.
- in this response, and I may have misinterpreted previous posts yoou state with tripod and flash, and the results are sharp like you thought they should be. I had not understood that you had used both tripod and flash together, I thought it was an either / or situation, but if you need flash to have a clean sharp image, to me that suggests the culprit is still camera shake, or shutter speed and subject motion blurr because the duration of the flash is in the 1-2/1000 range and will freexe any image irrespective of shutter speed

As for "extra software" with manual aperture lenses, that is not totally true. In fact there is less processing involved than with a zoom lens because with a manual aperture lens, you do enter the focal length, but once entered, it is absolutely fixed, with a zoom it must be updated at what ever refresh rate is in the camera's processor. Aside from how the camera aquires focal length, once the camera has focal length the calculation is the same for both types of lens, so I do not believe shake reduction would be introducing the error with your manual lenses.

Please note I am not looking to blame the user over camera only trying to identify the cause.

Last edited by Lowell Goudge; 01-13-2010 at 04:25 PM.
01-13-2010, 05:41 PM   #23
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Software designers put their maximum effort and testing into the key features of a software. Lesser features get less effort. Which is why your browser works virtually all of the time when doing routine things, but some oddball combination of plug-ins, java script, and other software might crash it. MF lens compatibility isn't as high on the priority list as AF lenses, so bugs are more likely with MF lenses.

I wasn't using either the green hexagon or the red square, I was using the ground glass. Now that I know it is not precise, I'll be paying more attention to the coloured geometry.

My comparisons were manual focused, hand held DA* f2.8 to SMC-A f2.8 lenses. Initial tests were DA* good, SMC-A bad. Subsequent tests were more random in the results. Focal length wasn't an issue, neither was shutter nor aperture -- compared like to like. Same camera body, same ground glass screen, same subject.

Tripod results, MF, both with flash (X sync + studio flash) and without (2 sec delay), were better all round with both lens types. The tripod takes the IS out of the equation, which is why I focused (bad pun) on that first.

Since manual focusing when on a tripod tends to be a bit more deliberate exercise (for me anyway), Marc's explanation is a very good possibility. My reliance on the less-than-accurate ground glass when handheld will be less optimal than when on a tripod. When handheld, I pick my plane of focus, then focus on it, then shoot. On a tripod, I'm more likely to rack the lens back 'n' forth to pick a focal plane that I like. That subtle difference may account for the results, considering the imprecise ground glass issue.


Last edited by Rusty Rat; 01-13-2010 at 05:53 PM.
01-13-2010, 05:58 PM   #24
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QuoteOriginally posted by Novocain Quote
Can someone else confirm this? I have a Pentax-A 50mm f/1.7 and it also asks for the focal length every time I turn the camera on.

I sometime have trouble with slightly blurry/fuzzy pictures as well. But I attribute it to my poor manual focusing skills and the shallow DOF since I like to shoot it wide open or close to it.
Yes, A 50 1.7 needs focal length info entered, shooting wide open can be tricky due to shallow DOF like you suspected.

Cheers, Mike.
01-13-2010, 08:55 PM   #25
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QuoteOriginally posted by Rusty Rat Quote
...I wasn't using either the green hexagon or the red square, I was using the ground glass. Now that I know it is not precise, I'll be paying more attention to the coloured geometry...
The green hexagon is fairly imprecise as well, though not as bad as the viewfinder screen.

In regards to replacement screens, I usually suggest (in order of decreasing price):
  • Katz Eye with Optibrite
  • Katz Eye w/o Optibrite
  • focusingscreen.com
  • jinfinance and other eBay merchants selling cut-down K1000 screens
I have personal experience with the two Katz Eye screens on my K10D. Anything else I might write is based on discussions with other users on this forum. A few considerations:
  • Katz Eye customer service is excellent. They also offer custom grids and other markings.
  • Katz Eye Optibright is worth it if you routinely shoot with lenses f/3.5 and slower
  • The Katz Eye w/o Optibrite is equivalent to the K3 from focusingscreen.com
  • Many users from this forum are very satisfied with their eBay screens
  • Jinfinance and other eBay screens have been known to frequently require shimming. In at least one circumstance, this has been true with Katz Eye as well.
These are the options I am aware of.

Steve
01-14-2010, 06:53 AM   #26
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QuoteOriginally posted by stevebrot Quote
The green hexagon is fairly imprecise as well, though not as bad as the viewfinder screen.

In regards to replacement screens, I usually suggest (in order of decreasing price):
  • Katz Eye with Optibrite
  • Katz Eye w/o Optibrite
  • focusingscreen.com
  • jinfinance and other eBay merchants selling cut-down K1000 screens
I have personal experience with the two Katz Eye screens on my K10D. Anything else I might write is based on discussions with other users on this forum. A few considerations:
  • Katz Eye customer service is excellent. They also offer custom grids and other markings.
  • Katz Eye Optibright is worth it if you routinely shoot with lenses f/3.5 and slower
  • The Katz Eye w/o Optibrite is equivalent to the K3 from focusingscreen.com
  • Many users from this forum are very satisfied with their eBay screens
  • Jinfinance and other eBay screens have been known to frequently require shimming. In at least one circumstance, this has been true with Katz Eye as well.
These are the options I am aware of.

Steve
Steve, I am not an expert on the entire range of pentax cameras, but the issues with shimming, at least to my memory are predominantly when split imaging screens are installed into the cameras using penta mirrors.

If this is incorrect, please correct me on this, but I am not aware of any issues installing split images in the *istD, K10D or K20D. all of which have screens that are physically the same size and are interchangeable between cameras,

my own experience with the Jinfinance screen ordered from e-bay is that the screen performs well and focuses accurately, Darkening occurrs at about F3.5 to F4 if you are off axis, (i.e. not alligned on the view finder) but otherwise is quite useable at F5.6 if you are careful.

With respect to focusing at F5.6 or smaller apertures, this is really only an issue if you focus with M42 lenses stopped down. If you focus wide open and then stop down while in Av mode (so the camera does the metering) there is no problem, and one of the reasons people go for a split image is to use manual focus fast lenses. At least that is my reason. Except for lenses 200mm or longer, do I have any prime lens (K or M42 mount) slower than F2,8 and most are F2 or faster.
01-14-2010, 07:39 AM   #27
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QuoteOriginally posted by stevebrot Quote

In regards to replacement screens, I usually suggest (in order of decreasing price):
  • Katz Eye with Optibrite
  • Katz Eye w/o Optibrite
  • focusingscreen.com
  • jinfinance and other eBay merchants selling cut-down K1000 screens

Steve
Thanks for the list. I'll be investigating the Katz Eye with Optibrite for my K20D as it is that camera that receives the lion's share of the MF work. I'm assuming the screen is user changeable and that the screen comes with any tools that may be necessary (e.g. tweezers). In the past I've routinely changed screens on 35mm and 645 film SLRs, but yet to try it on a DSLR. I'm assuming nothing extra to worry about, apart from dirt.
01-14-2010, 08:14 AM   #28
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Got all of the info I needed from the Katz website.

Thanks.
01-14-2010, 08:42 AM   #29
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QuoteOriginally posted by Rusty Rat Quote
Got all of the info I needed from the Katz website.

Thanks.
Good luck and I hope this solves your problem

Changing the screen is about a 10 minute job. Pretty simple really, but there have been some posts about people putting too much force and bending the frame a little. If it takes more than a slight push, don't force it, start over and try again.
01-16-2010, 09:16 PM   #30
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novocain, as others can confirm as well, you have to enter the FL using the 50-A f/1.7, if you have IS engaged (note that if you have the delay set on the shutter, the IS is switched off and you won't get the FL notice). I've found I get the best focus results with the 50-A by leaving the camera (K20) in AF, holding down the shutter button, and very slowly rotating the focus ring until the shutter goes off. I get more consistent large aperture focusing that way contrasted with MF even with a Katzeye split collar screen,
Brian
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