Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-12-2011, 08:56 PM   #76
Veteran Member
Smeggypants's Avatar

Join Date: Sep 2010
Posts: 1,536
QuoteOriginally posted by rhodopsin Quote
That's right

QuoteOriginally posted by Your article:
The Ee-A standard focusing screen for the EOS 5D is bright enough (and accurate enough) for manual focusing under most lighting conditions with virtually any EF lens regardless of maximum aperture. However, because of the design of the microlenses on the surface of the Ee-A, the depth of field shown through the viewfinder never appears be shallower than approximately f/2.8.

Therefore, when using a lens faster than f/2.8, the depth of field in the resulting photograph may be shallower than what's shown in the viewfinder if a working aperture larger than f/2.8 is selected. This effect can be readily seen when comparing the viewfinder image to the LCD screen during replay, if you take time to look for it.
Compared to ...

QuoteOriginally posted by Wheatfield Quote
Depth of field is a factor of the lens, not the focusing screen. I've heard that urban legend before, I thought it was horsepoo when I heard it, and I think it is horsepoo now, even though it has moved from urban legend to accepted but false fact.

So yet another source that says it isn't horsepoo afterall. And as the rest of us have seen the focussing screen is a factor in the DOF seen through the viewfinder.

04-13-2011, 01:21 AM   #77
Forum Member
Jan67's Avatar

Join Date: Oct 2010
Location: Prague
Photos: Gallery | Albums
Posts: 84
What about stock screen and shim ?

I am happy user of KatzEye split screen adjusted with the right shim.

I just wonder, that all delivered K-7 and K-5 with the stock screen and standard shim (0.40mm) actually have no chance to focus properly using viewfinder (independently if you are able to focus manually or not). Most users even don't know, if they don't read forums. If we have to adjust split screens, than stock screens have to be adjusted as well, right?

It seems that Pentax doesn't care for manual focuasing too much and skip some kind of adjusting in production. I understand that AF lens is sales priority for them. Anyway, they could at least inform and possibly add these 0.7$ shims to every K-5...

Thanks God that they sell at least right shims.
04-13-2011, 06:22 AM   #78
Senior Member




Join Date: Oct 2010
Location: france
Photos: Albums
Posts: 163
aaaa AF confirm doesn't work!

now I have an excuse ))
04-13-2011, 06:29 AM   #79
Site Supporter
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,698
QuoteOriginally posted by JohnBee Quote
...under the impression that AF confirm was a completely separate thing from the AF module?
I will join the chorus...NOPE! They are one and the same.

And the bad news is that the AF module, while very good, ain't that great, even when properly dialed in. That is even true if you are using the high-priced spread. (Ancient reference to margarine advertisement...) The problem not the electronics or assembly tolerance. Rather it is related to the size of the area being evaluated for focus and the fact that the camera has no idea what the subject actually is. For fine focus of most subjects, a split image screen will consistently outperform the the AF system. For macro or extremely limited DOF, a plain field screen may work even better.


Steve

04-13-2011, 06:31 AM   #80
Veteran Member




Join Date: Mar 2009
Location: Midwest
Photos: Gallery
Posts: 1,407
QuoteOriginally posted by Jan67 Quote
I am happy user of KatzEye split screen adjusted with the right shim.

I just wonder, that all delivered K-7 and K-5 with the stock screen and standard shim (0.40mm) actually have no chance to focus properly using viewfinder (independently if you are able to focus manually or not). Most users even don't know, if they don't read forums. If we have to adjust split screens, than stock screens have to be adjusted as well, right?
Most users probably don't join forums, you're right. Most users probably aren't quite as pixel-peeping oriented as we here in the forum are. Most users probably don't manual focus, either. I can't speak to why in the world Pentax would ship them like this - I don't understand it either. Nearly everyone I've spoken to ends up at .25... *shrug*.

QuoteQuote:
It seems that Pentax doesn't care for manual focuasing too much and skip some kind of adjusting in production. I understand that AF lens is sales priority for them. Anyway, they could at least inform and possibly add these 0.7$ shims to every K-5...

Thanks God that they sell at least right shims.
Yeah, completely agree.
04-13-2011, 06:32 AM   #81
Site Supporter
Site Supporter
aliasant's Avatar

Join Date: Feb 2010
Location: Stockholm
Photos: Gallery | Albums
Posts: 634
QuoteOriginally posted by dreamfoto Quote
aaaa AF confirm doesn't work!

now I have an excuse ))
hehehe
Exactly what I thought

Today I realised that I can turn of the green little annoying focus indicator.
I set the half pressed shutter activates AF to Off.

Finally! Now I can decide when I think its in focus. Still have a small FF problem though but Im talking to Pentax about getting shims from them.
I did try to remove the shim all together and that made it backfocus by about 10cm. Interesting.
Also put back my Katzeye and it works pretty well now but still s small FF by about 1 cm. Maybe a new shim at somewere between 0.20-0.35mm will do the trick.
04-13-2011, 06:54 AM   #82
Pentaxian
JohnBee's Avatar

Join Date: Sep 2008
Location: front of computer
Posts: 4,630
Original Poster
QuoteOriginally posted by Jan67 Quote
I am happy user of KatzEye split screen adjusted with the right shim.

QuoteOriginally posted by stevebrot Quote
a split image screen will consistently outperform the the AF system. For macro or extremely limited DOF, a plain field screen may work even better.

QuoteOriginally posted by aliasant Quote
Also put back my Katzeye and it works pretty well now but still s small FF by about 1 cm. Maybe a new shim at somewere between 0.20-0.35mm will do the trick.

I think many people are overlooking the potential catch-in focus function that can be used with manual lenses. And though this could easily be replaced with a split screen with static work, it can prove to be quite indispensable in other types of shooting. And so in this sense, a Katzeye really can't compensate. it can help!, but it won't compensate for the loss of that function.

However... I think the inherent differences between the camera AF and it's potential is now clearer. Though I remain perplexed by the fact that a camera could properly focus with fast lenses(1.4) using AF, whereas it cannot AF confirm the same lens while in MF.

Granted... this isn't the end of the world(and I think we we all know better...). Though it does come across as a bump in the road(so to speak) when we constrast such issues with earlier systems that seem to work better in this respect.

On a side note, I wish I still had my K200D to compare too as well. All I have at this time are two K20D's that have both been subject to annual service/adjustments from Pentax. And so I don't know if the AF systems are accurate due to having been adjusted or.. if they truly came that way.
04-13-2011, 07:17 AM - 1 Like   #83
Veteran Member
Smeggypants's Avatar

Join Date: Sep 2010
Posts: 1,536
QuoteOriginally posted by Wheatfield Quote
The hostility Smegma had was caused by him ignoring that I use a Katz-Eye and can manual focus very well with it, while he was insisting that I couldn't possibly get accurate manual focus at all.
I guess he's never heard of aftermarket screens.
ROFL. Wheatfield promised to ignore me, but just can't quite do it.

However in this thread he's now learned that focussing screens do actually show a wider DOF with fast lenses than is reality.

To correct the folllowing lie :

QuoteQuote:
while he was insisting that I couldn't possibly get accurate manual focus at all.
, I did nothing of the sort of course. Very disingenuous of this Wheatfield there and a cheating way of scoring his forum points.

04-13-2011, 07:32 AM   #84
Veteran Member




Join Date: Mar 2009
Location: Midwest
Photos: Gallery
Posts: 1,407
QuoteOriginally posted by JohnBee Quote
I think many people are overlooking the potential catch-in focus function that can be used with manual lenses. And though this could easily be replaced with a split screen with static work, it can prove to be quite indispensable in other types of shooting. And so in this sense, a Katzeye really can't compensate. it can help!, but it won't compensate for the loss of that function.

However... I think the inherent differences between the camera AF and it's potential is now clearer. Though I remain perplexed by the fact that a camera could properly focus with fast lenses(1.4) using AF, whereas it cannot AF confirm the same lens while in MF.

Granted... this isn't the end of the world(and I think we we all know better...). Though it does come across as a bump in the road(so to speak) when we constrast such issues with earlier systems that seem to work better in this respect.
Just to be clear, since I got 1) a replacement K-5 and 2) firmware 1.03, my AF system works quite well - at least as well as my K20D, and faster to boot. Catch-in-focus works quite well for most subjects. Testing with Bigma, I found that in extremely low contrast situations with (relatively) slow lenses, my K-5 FFs a bit. To contrast that, with the same lens and subject, the K20D hunts back and forth and often gives me a flashing green (can't focus) light. When it does lock, though, it's occasionally more accurate than the K-5, but still spotty. By comparison, a friend's CaNikon wouldn't lock on it either. But if I adjusted my point of focus just a bit to the right to find a strong vertical line, the focus on the K-5 locked in immediately, as did the other cameras.

In short, I have to work pretty hard to create situations in which my K-5 focus system fails (select light level, select low-contrast subject, etc).

The manual focus was off from day one, though. I set it up with the classic 45 degree angle to a yardstick and used a 135mm f2.8 lens, and it was quite obvious. Focus on 10, and 14 was in focus. And the DOF with that lens is pretty clear.

Last edited by jstevewhite; 04-13-2011 at 07:34 AM. Reason: clarity
04-13-2011, 08:47 AM   #85
Pentaxian
JohnBee's Avatar

Join Date: Sep 2008
Location: front of computer
Posts: 4,630
Original Poster
QuoteOriginally posted by jstevewhite Quote
Catch-in-focus works quite well for most subjects.
When you say this, are you refering to a manual focus lens?

Here's a quick test;

Take a manual focus lens(50mm - 135mm) set it at F/2.8, enable catch-in focus, select a target at/or about 10 feet from you, depress the shutter and begin to focus. Once the shutter releases, check your results.

Are the images accurate?

I performed this test on both my K20D and K-5 and the K-5 images were all out of focus. While the K20D was "mostly" in focus. I won't go as far as saying they were all in focus, but in contrast to the K-5 which had none in focus, the K20D did quite well.

PS. this is with SMC-A lenses or a lens with a metal flange that short the pins thus enabling CIF. Otherwise, they won't work.

Oh and FTR, my K-5 is spot on in AF most all but the lowest of light conditions. At which point the AF assist lamp picks-up whats needed to keep-up.
04-13-2011, 09:11 AM   #86
Veteran Member




Join Date: Mar 2009
Location: Midwest
Photos: Gallery
Posts: 1,407
QuoteOriginally posted by JohnBee Quote
When you say this, are you refering to a manual focus lens?

Here's a quick test;

Take a manual focus lens(50mm - 135mm) set it at F/2.8, enable catch-in focus, select a target at/or about 10 feet from you, depress the shutter and begin to focus. Once the shutter releases, check your results.

Are the images accurate?

I performed this test on both my K20D and K-5 and the K-5 images were all out of focus. While the K20D was "mostly" in focus. I won't go as far as saying they were all in focus, but in contrast to the K-5 which had none in focus, the K20D did quite well.

PS. this is with SMC-A lenses or a lens with a metal flange that short the pins thus enabling CIF. Otherwise, they won't work.

Oh and FTR, my K-5 is spot on in AF most all but the lowest of light conditions. At which point the AF assist lamp picks-up whats needed to keep-up.
Yes, I'm quite familiar with catch-in-focus. I use it with my Tamron 180 f2.5 quite often, particularly for hand-held macro work (as it's easier to set CIF and lean in than to jigger the ring while trying to keep from swaying even 1 mm), and several other manual-focus lenses (a Takumar 80-200 f4, Tamron 28mm, Tamron 80-200 f4), . My K-5 works very well with catch-in-focus. Here's an example. It was breezy, and the cherry tree branches kept moving, so I used CIF with my Tamron 180 (to be fair, it was stopped down a bit, but the depth of field was such that I couldn't get a sharp image focusing manually because of the breeze):


Last edited by jstevewhite; 04-13-2011 at 09:13 AM. Reason: clarity
04-13-2011, 09:16 AM   #87
Pentaxian
JohnBee's Avatar

Join Date: Sep 2008
Location: front of computer
Posts: 4,630
Original Poster
QuoteOriginally posted by jstevewhite Quote
to be fair, it was stopped down a bit, but the depth of field was such that I couldn't get a sharp image focusing manually because of the breeze
My experience has been that it works very well at f/3.5 and above. However by f/2 things begin to degrade as the aperture gets wider. By f/1.4 the images are unusable. And so I'm leaning toward the fact that the system AF doesn't do well at wider apertures(most likely). Not exactly sure as to why at this stage.
04-13-2011, 09:41 AM   #88
Veteran Member




Join Date: Mar 2009
Location: Midwest
Photos: Gallery
Posts: 1,407
QuoteOriginally posted by JohnBee Quote
My experience has been that it works very well at f/3.5 and above. However by f/2 things begin to degrade as the aperture gets wider. By f/1.4 the images are unusable. And so I'm leaning toward the fact that the system AF doesn't do well at wider apertures(most likely). Not exactly sure as to why at this stage.
DOF drops significantly as magnification goes up. A 180mm lens has (approximately) 4x (ok, 3.6x) the magnification of a 50mm lens, so at similar distances, will show similar DOF at higher aperture numbers (in this case, I would say f4 with a 180 at the same camera-to-object distance will have approximately the same DOF as a 50mm @f2)

Indoor images @f2.5 with the same manual focus lens (180mm - one of my all-time favorites) have yielded sharply focused images. I think you should get your camera checked, mate.
04-13-2011, 09:54 AM   #89
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,895
So, to sum up , I think steephill (posting on a similar thread in the other forum 'Front focus with manual lenses') summarised the issue best:

"As has already been said the focus confirmation indicator is a bit vague, try getting focus confirmation from both directions i.e. from infinity then from minimum focus and you will see this easily. This happens because the AF system which provides the focus confirmation signal is also a limited aperture system. It is good enough when stopped down but again not good enough for wide aperture work."
04-13-2011, 10:02 AM   #90
Veteran Member




Join Date: Dec 2009
Location: Deep Forest
Posts: 630
Understanding Camera Autofocus

An AF lens 'hunts' for focus. Consider how AF lens 'hunts' for focus in low light. The same 'search', 'find', 'adjust' actions happen in good light, but so fast it seems the lens moves directly to focus, when in fact it has performed those same steps in milliseconds.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
af, camera, dslr, focus, indicator, k-5, k-5 ii, k-5 iis, k5, lens, mf, pentax k-5
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
M42 adapter for pentax mount with focus confirm? zoe Pentax SLR Lens Discussion 6 03-24-2013 09:35 AM
DA* 16-50: AF confirm issues at infinity nicolas1970i Pentax SLR Lens Discussion 2 12-27-2010 02:56 AM
Does the K-X have manual focus confirm with ...... dude163 Pentax SLR Lens Discussion 13 05-22-2010 02:46 PM
Confirm mount. Simon23 Pentax SLR Lens Discussion 4 06-09-2009 03:15 PM
Can someone confirm that there is a sigma 100-300 hsm F4 Torphoto Pentax SLR Lens Discussion 8 05-06-2008 08:13 AM



All times are GMT -7. The time now is 12:06 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top