How do you think a self adjustment could invalidate my warranty? do you think that any minor sign on the screw that would indicate that I have tried doing it myself would invalidate warranty?
-
Welcome to the new forums! Please read this first. For known issues we are working to resolve, click here.
M8 backfocus test - please comment
- Thread starter steward84
- Start date
I'm really sorry, but I'm not sure I get your point other than to be argumentative. The original poster gave you a link to real life examples in which the backgrounds were out of focus. The reason He/she said they weren't good photos to judge focus because is that they were effected by back focus - he/she just didn't know it yet. These photos were not close-ups, but average to long distance and the backgrounds are clearly tack sharp and the intended plane of focus - not. Yes movement blurred the photos but the ground around the subject is not moving, and if the shooter was unsteady, the background would have been blurry also. The poster also showed us a test - with camera on tripod - that clearly shows a back focus of 3 inches at whatever shooting distance was.
As to you reply to "my" post, I never said I could focus in "real world" conditions to within a 1/4", I just mentioned that in comparison to the 3" that the poster's camera was off. Do you even own an f1.4 lens? If so, how can you dare say that spot on focusing is not only unimportant, but impossible? I can promise you, if you are shooting a person from a distance of -say- 4 ' at f1.4, you better have your lens focused "darn" close if you want the subjects eyes to be sharp "AT ALL". A 1/4" backfocus problem will be pushing the boundries and the posters test proves it.
Nobody's nit-picking here. The result of the posters test IS "ridiculously" unacceptable (3 inches for Pete's sake). The posters, & now "my" concerns are more than valid. Why are you trying to defend Leica's position on this and what is there to defend? I can't express how it pains me to say this, but shame on Leica for knowing (they admit it), but not making it known that two of their "all-time" best lenses, of the most important focal length to rangefinder photography (35mm), are basically "no good" with the M8. Based on Leica's own claims, these lenses should be stricken from the lens compatability list.
As to you reply to "my" post, I never said I could focus in "real world" conditions to within a 1/4", I just mentioned that in comparison to the 3" that the poster's camera was off. Do you even own an f1.4 lens? If so, how can you dare say that spot on focusing is not only unimportant, but impossible? I can promise you, if you are shooting a person from a distance of -say- 4 ' at f1.4, you better have your lens focused "darn" close if you want the subjects eyes to be sharp "AT ALL". A 1/4" backfocus problem will be pushing the boundries and the posters test proves it.
Nobody's nit-picking here. The result of the posters test IS "ridiculously" unacceptable (3 inches for Pete's sake). The posters, & now "my" concerns are more than valid. Why are you trying to defend Leica's position on this and what is there to defend? I can't express how it pains me to say this, but shame on Leica for knowing (they admit it), but not making it known that two of their "all-time" best lenses, of the most important focal length to rangefinder photography (35mm), are basically "no good" with the M8. Based on Leica's own claims, these lenses should be stricken from the lens compatability list.
Theo Peters
Well-known member
I am agree with you Rollei.
Peter Nelson
Veteran Member
I own (1) 24mm f/1.4, (1) 35mm f/1.4, (3) 50mm f/1.4 and (1) 85mm f/1.2. So I have had to learn DOF.
There are many depth of field charts available on the web. If you look at a few of them you will see DOF for an 85 f/1.2 wide open at 3 ft is only about 1/4" but at 15 ft it's much greater, more than 3", I don't have the site book marked but I did find another (custom charts) and I entered the 35mm f/2 lens (the lens in question) and the DOF at f/2 and 15 ft would be at least 6.5 feet. At 10 ft distance the DOF is only 2.81 feet.
I'm using 15 ft because that's what the distance to his subjects look like to me.
My point is at 15 feet his 3" DOF slight unsharpness one way or the other in an action photo could not matter. So even if his ruler test indicates a not perfectly sharp image at the 20" mark it was still reasonably sharp. The 20" number was very readable if it was blurry then I'd say there was a problem.
From his 20" to 17" the numbers did get sharper but only a small degree.
So at 15 ft distance his small unsharpness that I saw in his test would be irrevelent. 15 ft distance at f/5.6 its almost 27 DOF.
So I put it down to focusing error.
Don't take my word for it.
Please go look at a few DOF charts, find one that is clear to you (some of them are difficult to use, there are some easy ones to understand) and check for yourself a 35mm f/2 lens DOF, check 5', 10' & 15' distances at f/2 and DOF.
I understand that the M8 is not full frame so you would have to figure the DOF using the 1.3 crop, yes it will be less than a 35mm f/2 on FF.
--
Artist Eyes
There are many depth of field charts available on the web. If you look at a few of them you will see DOF for an 85 f/1.2 wide open at 3 ft is only about 1/4" but at 15 ft it's much greater, more than 3", I don't have the site book marked but I did find another (custom charts) and I entered the 35mm f/2 lens (the lens in question) and the DOF at f/2 and 15 ft would be at least 6.5 feet. At 10 ft distance the DOF is only 2.81 feet.
I'm using 15 ft because that's what the distance to his subjects look like to me.
My point is at 15 feet his 3" DOF slight unsharpness one way or the other in an action photo could not matter. So even if his ruler test indicates a not perfectly sharp image at the 20" mark it was still reasonably sharp. The 20" number was very readable if it was blurry then I'd say there was a problem.
From his 20" to 17" the numbers did get sharper but only a small degree.
So at 15 ft distance his small unsharpness that I saw in his test would be irrevelent. 15 ft distance at f/5.6 its almost 27 DOF.
So I put it down to focusing error.
Don't take my word for it.
Please go look at a few DOF charts, find one that is clear to you (some of them are difficult to use, there are some easy ones to understand) and check for yourself a 35mm f/2 lens DOF, check 5', 10' & 15' distances at f/2 and DOF.
I understand that the M8 is not full frame so you would have to figure the DOF using the 1.3 crop, yes it will be less than a 35mm f/2 on FF.
--
Artist Eyes
I had a long chat a few weeks ago with an architectural photographer who uses Canon DSLRs and lenses. He talked about a years long struggle he had with early Canon cameras and lenses showing this same back focus problem. He indicated that his most recent cameras 1DsMII seemed to have fixed the problem.
Canon may have made some slight adjustments in their camear's autofocus to compensate for the problem. It seems that this is a transition to digital issue. Most of the lenses that we use today were designed for film. It's not practical to just scrap everything and start from scratch with new cameras and lens designs.
Maybe a few years out this will all be worked out. In the meantime:
I can't focus my M camears (6,7,8) most of the time with sufficient precision to see the problem in the field. If there were a case of a static subject and sufficent time to focus carefully it would seem that moving the focus point forward slightly when shooting higher apertures would solve the problem (maybe this is what my freind's new Canon does automatically).
All systems will have some design limitations. A good shooter will learn to adapt and still get good images.
Canon may have made some slight adjustments in their camear's autofocus to compensate for the problem. It seems that this is a transition to digital issue. Most of the lenses that we use today were designed for film. It's not practical to just scrap everything and start from scratch with new cameras and lens designs.
Maybe a few years out this will all be worked out. In the meantime:
I can't focus my M camears (6,7,8) most of the time with sufficient precision to see the problem in the field. If there were a case of a static subject and sufficent time to focus carefully it would seem that moving the focus point forward slightly when shooting higher apertures would solve the problem (maybe this is what my freind's new Canon does automatically).
All systems will have some design limitations. A good shooter will learn to adapt and still get good images.
Theo Peters
Well-known member
Hello Peter,
Having for 20 years or longer a Leica M4 with 3 lenses, and have not 1 focus problem in all these years, Ihad it now with my M8, the camera is back to New Jersey.
Having said that: when the camera is on a tripod with a non moving subject and you focus point is on that subject what you want to have in focus.
Then it should be in focus and sharp. If I change the f stops, my focus point should be still sharp and there is only a changing in DOF, NOT in the focus point.
If the focus is drifting away when I change my F stops then there is a problem with the lens or a combination camera and lens.
Theo
Having for 20 years or longer a Leica M4 with 3 lenses, and have not 1 focus problem in all these years, Ihad it now with my M8, the camera is back to New Jersey.
Having said that: when the camera is on a tripod with a non moving subject and you focus point is on that subject what you want to have in focus.
Then it should be in focus and sharp. If I change the f stops, my focus point should be still sharp and there is only a changing in DOF, NOT in the focus point.
If the focus is drifting away when I change my F stops then there is a problem with the lens or a combination camera and lens.
Theo
tashley
Veteran Member
I have no idea how they would tell or how they would react - I was just sounding a note of caution and saying that this would be AYOR...
(ay your own risk)
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
(ay your own risk)
--
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
digicam
Forum Enthusiast
I just returned the M8 which I bought yesterday.
It focused with about 1-2mm offset from the actual distance. The final verdict was quite easy, because it did not focus at infinity.. You may also check if you have a vertical alignment issue too. Because of the excellent parallax correction, when you miss the horizontal alignment, as a result you usually end up having a very slight vertical alignment too. (You won't even notice unless you try to find it)
I have a collection of Leica and Leica copies. Russian copies have this problem all the time. So I'm used to it, and can do the repair as well.
But seeing it on a brand new M8 was quite surprising.
My new camera is on the way.
Seyhun
--
http://gallery.slrdigital.org
It focused with about 1-2mm offset from the actual distance. The final verdict was quite easy, because it did not focus at infinity.. You may also check if you have a vertical alignment issue too. Because of the excellent parallax correction, when you miss the horizontal alignment, as a result you usually end up having a very slight vertical alignment too. (You won't even notice unless you try to find it)
I have a collection of Leica and Leica copies. Russian copies have this problem all the time. So I'm used to it, and can do the repair as well.
But seeing it on a brand new M8 was quite surprising.
My new camera is on the way.
Seyhun
--
http://gallery.slrdigital.org
--the depth of field of a 35mm lens is the same whether or not its used on a cropped camera. to prove this take a ff photo with your 35mm lens on an m3-m7 and then one with the m8. then compare the portion of the ff printwhich equals the coverage of the m8 whith the m8 print and the depth of field will be the same. The lens has no idea whats behind it visa vie depth of field. I think the confusion resaults from the fact that your 35mm cron or whatever on the m8 looks like a fifty mm on ff for coverage but the 35mm cron still has the depth of field of the 35mm lens not the fifty even though it now thinks its a fifty.
As to the back focus issue as I mention I have never noticed this problem in fifty years of using leicas and scores of other rangefinders, and the 35mm cron is by far my most used lens. that however doesnt mean its not there. I wonder if this is a problem in all the 35 crons or just some of them. I wonder if this is a problem with all lenses to a greater or lessor degree. On a reflex with ground glass you could get the center sharp more often than not but if there is a focus shift in the center then the rest may drift out of focus. I am guessing if Leica's information posted is correct that this is an inhearent problem with lens design and the new world of digital has made us more aware of it cus film is almost never flat.
One point about focusing the Leica should be mentioned that may help aleviate some of your focus errors. The design of the Leica rangefinder is such that it is both a split image and a co-incidnece range finder. That is to say you move the two images in the rangefinder till they are super-imposed (co-incident) and you can use the top and bottom edges to align virticles in your frame to the rangefinder secondary image (splite image) With a good vertical or horizontal line in the frame( for horizontal lines turn the camera to the virtical position) use the split image as its far more accurate than the co-incident. Irwin Putts has a really good discussion of rangefinder accuracy on his web site but I dont have the link right now someone will. He says the split image is capable of something in the order of about ten times as accurate if I remember correctly. He demonstrates that using the co-incident method of focusing has a much greater degree of difference when focusing on the same target several time in succession. He did not mention ground glass focusing in this discussion but I believe the same issues would apply in that a person focusing manualy his dslr several times at the same target will get slightly different focus each time.
One other urban myth about the Leica and rangefinder cameras is that they are more accurate focusing wide angle lenses than focusing long focus lenses. This is untrue the focusing accurace is the same the rangefinder has no idea of what lens is on the camera. The problem is longer focus lenses require greater focusing accuracy than shorter lenses given the same f stop.
bosjohn aka John Shick [email protected]
I hope you didn't take the "newbie" comment too personally. I'm just seeing a huge influx of new attitudes (due to the creation of the M8) on these forums by people who are new to rangefinder photography but are basing their purchase, lens choice, opinions (positive & negative), and philosophy in general, upon their previous SLR experience/mentality. While they certainly share some principles, the rangefinder "shines" in the wide angle to (very) short telephoto range and certain shooting styles, and the SLr "shines" in the extreme ends of the spectrum (meaning macro and telephoto) along with a different set of shooting styles and purposes. The 35mm (film equiv focal length) is, always has been, and always will be the best "stand alone" lens for any rangefinder camera. It saddens me a little to hear you say that if you had known about the 35mm problem you would have gotten a different lens. You chose exactly right the first time. You are correct: "We are all newbies" in the M8 arena and I would have been bitten also had my timing/finances allowed. But the difference between the seasoned rangefinder users and the newbies is in what we consider "being bitten" is and how we "take" it.
On another note, here's another test. Have you checked your camera/lens/rangefinder for infinity accuracy? Excuse me if you already know this, but focus your lens on a contrasty object approx. 200 feet away. Now look at the distance scale on the lens. Is it on the infinity mark? If not, you may have and adjustment problem of a slightly different type but is something to tell Leica when you send it in.
On another note, here's another test. Have you checked your camera/lens/rangefinder for infinity accuracy? Excuse me if you already know this, but focus your lens on a contrasty object approx. 200 feet away. Now look at the distance scale on the lens. Is it on the infinity mark? If not, you may have and adjustment problem of a slightly different type but is something to tell Leica when you send it in.
Peter Nelson
Veteran Member
Hi Theo,
Your are correct. I'm wondering if the OP wears glasses and if somehow he is not getting the focus point nailed.
BTW I know the differences between DOF and point of focus.
Also if the point of focus is 15 ft distance from the lens and your 35mm lens is at f/2 then the DOF is as I described in my eairlier post is 6.5 feet?
That's around 3 feet in front of the point of focus and 3 feet behind.
So explain how a 1 1/2" to 3" focus error makes the subject out off focus.
I stll think the OP focusing error is the most likley mistake here.
I have to go I'll be back.
--
Artist Eyes
Your are correct. I'm wondering if the OP wears glasses and if somehow he is not getting the focus point nailed.
BTW I know the differences between DOF and point of focus.
Also if the point of focus is 15 ft distance from the lens and your 35mm lens is at f/2 then the DOF is as I described in my eairlier post is 6.5 feet?
That's around 3 feet in front of the point of focus and 3 feet behind.
So explain how a 1 1/2" to 3" focus error makes the subject out off focus.
I stll think the OP focusing error is the most likley mistake here.
I have to go I'll be back.
--
Artist Eyes
Theo Peters
Well-known member
Hi Peter,
Thanks for you response, and yes if the OP wear glasses he should have an diopter and also the 1.25 magnifer, that helps a lot for lenses longer then 50 mm to get the picture in focus.
Still my guts feeling said that some lenses are good for the film M camera's but not for digital, thinking about the flatness of the sensor comparing to film?, to many camera's M8 have back focus problems.
My 2 cents.
Theo
Thanks for you response, and yes if the OP wear glasses he should have an diopter and also the 1.25 magnifer, that helps a lot for lenses longer then 50 mm to get the picture in focus.
Still my guts feeling said that some lenses are good for the film M camera's but not for digital, thinking about the flatness of the sensor comparing to film?, to many camera's M8 have back focus problems.
My 2 cents.
Theo
tashley
Veteran Member
With respect, when checking infinity you need an object several miles away and by far the best thing to use is the moon. 200 Metres is far far too close.
Tim
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
Tim
--
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
tashley
Veteran Member
Peter, you are being sensible but I am afraid you are wrong. The 35 lux and cron DO backfocus at the centre of the field of view between f2.8 and 5.6 or 8. It is a known issue, Solms has acknowledged it, I have tested it on three lenses on three bodies scientifically and exhaustively and many others have done the same thing with many replicating my results.
Tim
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
Tim
--
Gallery: http://tashley1.zenfolio.com/
Blog: http://timashley.wordpress.com/
steward84
Forum Enthusiast
Never personally taken, no worries!
Interestingly enough, I now think the 28mm might be my better choice. With the 1.3 crop factor that puts me right about the classic 35mm focaL Length. The original 35mm would have been my "normal" lens - I will keep it for a bit, see if I can live with the issues. I say this only because I waded through the 12 pages of posts on this issue over on the LUF which Tim references elsewhere, and there may be a workaround via focusing then reframing for the exposure. That may well be a pain not worth the trouble, though.
I have ordered a Zeiss Biogon 28mm, f2.8 and asked for overnight delivery - we'll see soon enough if my M8 needs a focus adjustment. Would you be interested in the results?
Yes - I think the term "newbie" should be applied to the folks at Solms as well! Thanks for your input in all these issues.
--
-Steve
'Living is not enough -- we have to talk about it' -(Samuel Beckett)
steward84
Forum Enthusiast
Hi Seyhun - the M8 that you had to return, just curious as to which lenses gave you focus trouble
--
-Steve
--
-Steve
Peter Nelson
Veteran Member
Tim,
I trust you.
How does the backfocus effect the focus point 15 ft from the lens at f/2.8?
I think the DOF as above would be at least 4 ft in front of and 4 ft behind the point of focus.
I'm having trouble understand why the OP 3" backfocus would be a concern with such a great DOF.
--
Artist Eyes
I trust you.
How does the backfocus effect the focus point 15 ft from the lens at f/2.8?
I think the DOF as above would be at least 4 ft in front of and 4 ft behind the point of focus.
I'm having trouble understand why the OP 3" backfocus would be a concern with such a great DOF.
--
Artist Eyes
--the depth of field would not be three feet in front and three feet in back. the acceptable depth of field towards the lens is less than that away form the lens so it would be more like two feet in front and three in back.
bosjohn aka John Shick [email protected]
Marijn Bezuijen
Well-known member
I believe this is a very real problem and is purely related to the lens, not the camera body.
The reason main reason why I say this is that the concept of focus shift with aperture change is well known and documented. It is a result of spherical aberration (which is also exhibited by aspherical lenses). Zeiss states that they have specifically designed their ZM range (with the exception of the 50mm C-Sonnar) to minimise this effect. Leica appears to have not done so for some of their lenses, as the effect is rather strongly present.
I am also not surprised that this is something that becomes apparent with the M8. The resolution of the sensor and the ease of pixel peeping with this camera I believe has more to do with it than any other inherent difference between film and digital. However, if anyone knows other fundamental differences that could cause the problem to occur on the M8 and not on film, please to enlighten me.
Also, I see an inherent difference between SLR's and rangefinders here. An SLR will normally focus at viewing aperture, which is wide open, so shots wide open should be in perfect focus, whereas focus could shift backwards for smaller apertures. My Nikkor 50/1.2 shows this very clearly on the D200 and in fact is very clearly unsharp at f/4.0 because of this. At f/11, DOF makes up for the focus error.
Now with a rangefinder, the manufacturer can choose which aperture to calibrate the focusing cam for. Zeiss appear to have chosen f/2.8 for the C-Sonnar.
What I would do if I had a lens that suffered from such an issue is find out at which aperture the focus is perfect and focus a tad further for larger apertures and a tad closer for smaller apertures. I use a similar trick with certain lenses on a DSLR.
The reason main reason why I say this is that the concept of focus shift with aperture change is well known and documented. It is a result of spherical aberration (which is also exhibited by aspherical lenses). Zeiss states that they have specifically designed their ZM range (with the exception of the 50mm C-Sonnar) to minimise this effect. Leica appears to have not done so for some of their lenses, as the effect is rather strongly present.
I am also not surprised that this is something that becomes apparent with the M8. The resolution of the sensor and the ease of pixel peeping with this camera I believe has more to do with it than any other inherent difference between film and digital. However, if anyone knows other fundamental differences that could cause the problem to occur on the M8 and not on film, please to enlighten me.
Also, I see an inherent difference between SLR's and rangefinders here. An SLR will normally focus at viewing aperture, which is wide open, so shots wide open should be in perfect focus, whereas focus could shift backwards for smaller apertures. My Nikkor 50/1.2 shows this very clearly on the D200 and in fact is very clearly unsharp at f/4.0 because of this. At f/11, DOF makes up for the focus error.
Now with a rangefinder, the manufacturer can choose which aperture to calibrate the focusing cam for. Zeiss appear to have chosen f/2.8 for the C-Sonnar.
What I would do if I had a lens that suffered from such an issue is find out at which aperture the focus is perfect and focus a tad further for larger apertures and a tad closer for smaller apertures. I use a similar trick with certain lenses on a DSLR.
Peter Nelson
Veteran Member
35mm format
35mm lens
f/2.8
distance 15 ft.
for that distance, near focus limit of DOF =11.9 ft.
for that distance, far focus limit of DOF=20.3 ft.
So now in the real world how does the 1 1/2" to 3" backfocus cause an issue?
I still think the OP did not nail the focus in his action sample pic's.
--
Artist Eyes
35mm lens
f/2.8
distance 15 ft.
for that distance, near focus limit of DOF =11.9 ft.
for that distance, far focus limit of DOF=20.3 ft.
So now in the real world how does the 1 1/2" to 3" backfocus cause an issue?
I still think the OP did not nail the focus in his action sample pic's.
--
Artist Eyes
Keyboard shortcuts
- f
- Forum