Backfocus Tests on M-Lenses

[MP3]

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Hi Folks

 

Did your Noct consistently backfocus for 1 inch at f1 ??

 

I did the test with my M-lenses lineup from 25mm onwards, by taking shots continously at a horizontal fine ruler. Once focus was set at the maximum aperture, I do not alter the focus. Just take subsequent shots at different apertures - stopped down every stop. I'm shooting at around 1m.

 

CV25P

28Cron

35Cron(IV)

35Cron(asph)

35Lux(asph)

50Lux(asph)

50Noct(IV)

75Cron

 

Though, it may not be perfectly vigourous. The test serves well to give me the answer.

 

I committed the test because I receive my discounted Noct this early May (Hi Eoin, hope you got yours in great shape) and found the focus at f1 is for sure challenging, but seems out always no matter how careful I did the focusing (fix objects).

 

Concisely,

- the 50 Lux Asph and 75 AA are spot on, just perfect at any apertures.

- CV25P, 28Cron, 35Cron(IV) and 35Cron(Asph) all performs great in the test. This group may exhibit very slight frontfocus (~0.25 inch) at max. aperture but just spot on when stopped down half stop to one stop. DOF also perfectly covering the intended focus area when stopped down beyond f2.8 or f4.

- My Lux 35 Asph is near spot on when wide open, however, it backfocus not gradually but quickly when stopped down 1 stop by 1 - 2.5 inch. DOF will only cover the intended focus area WELL when stopped down beyond f5.6.

- My Noct consistently backfocus for 1 inch at f1 and the backfocus stretch to 2.5-3 inch when stopped down. Seems never in good tack sharp focus.

 

Now what would you suggest me to do =)

 

 

My collected data below:

Leica M-Lenses Backfocus Records (b/f means backfocus in inch):

 

CV 25P f b/f

4 -0.25

5.6 0.00

8 0.25

 

28/2 Asph f b/f

2 -0.25

2.8 0.00

4 0.50

5.6 1.00

8 1.50

 

35/2 4th f b/f

2 -0.25

2.8 0.00

4 0.50

5.6 1.00

8 1.50

 

35/2 Asph f b/f

2 -0.25

2.8 0.00

4 0.50

5.6 1.00

8 1.50

 

35 Lux Asph f b/f

1.4 0.25

2 1.00

2.8 2.50

4 2.50

5.6 2.50

8 2.50

 

Noct * f b/f

Call for Service 1 1.00

1.4 1.50

2 2.00

2.8 2.50

4 3.00

5.6 3.00

8 3.00

 

50 Lux Asph f b/f

1.4 0.00

2 0.25

2.8 0.50

4 0.50

5.6 0.75

8 1.00

 

75/2 Asph APO f b/f

2 0.00

2.8 0.40

4 0.50

5.6 0.75

8 0.75

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[BerndReini]

I've researched this a lot and it is a well known problem ("compromise") with the Noctilux. Supposedly it is adjusted to focus perfectly at medium distances as opposed to other lenses, which are adjusted for perfect focus at 1m. Try focusing on something say 10-15ft from the camera. The focus should be spot on. The workaround for portraits with the Noctilux is to focus on the tip of people's noses instead of their eyes. You get used to it quickly and it is an acceptable compromise for a lens with such beautiful drawing.

[MP3]

Dear Bernd

 

I'm so glad that you've gone through the research on the topic. So from your experience, do you mean my Noct is in fact up to current Leitz Noct standard and not a particulat lemon? I'm just interested to know the fact regarding these high priced gems - Their prices just keep soaring. If the fact is these compromise is inevitable and common to all Noct, I will train myself up and let it grow on me.

 

I shall also test it in medium distance to see any difference. Thanks for your great input.

[Guest guy_mancuso]

Honestly what i am trying to figure out and can't seem to come to a reason, maybe i am clearly missing something here . But my thoughts are if you focus any RF lens or any lens on any body and it is in focus at a certain point and than stop the lens down than that critical focus should never ever change , granted you don't move the focus. What in the world does the aperture ring have to do with it. if your nailing a shot at 1.4 than stop it down to 2.8 nothing should change. The elements of the lens has not changed your distance has not changed . What am i missing here.

[JWW]

I posted my success last month on getting 5 lenses focused when I bought a 75mm Summilux that backfocused about 1ft at 12 ft away. Please note that at minimum distance, the focus was ok, but worsened with distance. I tweaked the far adjust on the M8 with the allen wrench to get the 75mm spot on at 12ft distance, which made it slightly front focused at minimum distance. I just had to move it a smidge. My other lenses were still ok, with focus moved up slightly but well within the DOF of these lenses. I still have the 30% coupon and am considering the Noctilux but keep thinking that I may be only able to custom tweak the M8 for either my 75mm Summilux or Noct but probably not both unless they are totally matched. Btw I spoke at length with Don at DAG and he can shim if you send the lens in.

 

Jan

[MP3]

Guy, this is the focus shift RF lens and even SLR will exhibit when one stop down the lens. From lens literature, this is an inherent characteristic due to residual spherical aberration if I remember correctly. Every len has but just a matter of extent. Fine lens example will have the backfocus covered up nicely when they stop down due to the extended dof.

 

Jan, if what you mention is true, then I shall bear no hope on my Noct as it already backfocused 1 - 3 inches at close sudject distance of ~1m. I'll try it out at 8 to 10 feet to see how is the results.

 

And here is the verdict - same framing, focused at the letter 5 on the ruler as indicated in M8 RF viewfinder. Focus ring was then untouched, just stopped down and repeat the shots. The pictures are from f1, 1.4, 2, 2.8, 4, 5.6, then finally f8.

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[Eoin]

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Matthew, it looks like f:/1 is spot on, f:/1.4, 2.0, 2.8 are off and f:/4 to a lesser extent but just usable. Beyond seems Ok. It can't be right to expect users to accept this level of performance.

 

While I'm still waiting for my 30% Nocti, I will be very disappointed should it exhibit this level of miss-focus. Thankfully I have not had may problems with focus other than user error in real shooting situations, there are times however I would have expected slightly sharper results then I achieved but just put them down to my own error. Interesting results you post here, food for thought. Thanks!.

[Guest guy_mancuso]

Thanks Eoin that explains it better .

[Eoin]

Thanks Eoin that explains it better .

 

LOL, and who says life has to be complicated. Glad you could follow my idiots guide to back focus ramblings.

[Guest guy_mancuso]

ROTFLMAO , i do understand the residual spherical aberration issue. At least i think i do . LOL

[MP3]

Come on. Guy and Eoin. My senior members here. Sorry if I put it too complicated =)

[Eoin]

Sorry Matthew, I was just a giving Guy a poke!.

Like I said food for thought with two new arrivals due for my bag, but they either perform or "hi....ho" it's back to Solms they go. Bottom line is the lens either preforms at all apertures or it's not worth having in the bag regardless of "residual spherical aberration allowance" or whatever it's called. I pay good money for the best, which is what I expect, nothing less.

[Guest guy_mancuso]

Just trying to get the brain to function this morning Matthew. 2 cups of Espresso and still not getting it done. LOL

 

Your test is very interesting though.

[Guest guy_mancuso]

Eoin the Nocti just does not do it for me. i know many folks love ths lens but for some reason it just seems too limited given the money even at 30 percent off. Maybe i'm crazy. Guess maybe i should buy one and try it for awhile, really the only way to see if something works for you. Certainly won't lose any money with it

[jaapv]

. I pay good money for the best, which is what I expect, nothing less.

 

So what 1.0 lens is supposed to be better - with the Noctilux you buy the best - and the worst. Doesn't do anything for me either, I agree, Guy.

[Guest guy_mancuso]

I think part of it for me is having the wonderfull 50mm Lux first. Damn the Lux is really hard to beat, probably in my book the best 50mm lens i every used. That is saying a lot , I have pretty much tried them all. The drawing on the Lux is just so beautiful and the tab focusing and size makes it a huge winner for me. Just have a hard time justifying the Nocti and you all know me i will buy almost anything. This one though stops me in my tracks from hitting the add to cart button

[carstenw]

I also played with a Noctilux briefly, and after getting over how fast it is, and how nice it feels on the M8, I pretty quickly decided that this was a lens I wouldn't need any time soon. I will probably buy one some day, when I get bored and my wallet gets off lifesupport, but until then, I won't miss it. I am far more curious about the 50 Lux pre-Asph, to be honest, or even an older Summitar or something.

[Eoin]

Guys, guys, not to dump all over this man's thread but please indulge my fantasy regarding the Nocti. I have no idea if it will be "THE" lens for me, I want something a little softer but not quite as tight as the 75's (I already have the 75 cron). I already have a summicron 50 and it's getting there, the Nocti is supposed to be softer from f/2 - f/4 than the Summicron and if it does what I want it for which is portrait type stuff I'll be happy.

 

If it's not "THE" lens, my search will continue with an extra €1000 in my back pocket from the sale of the "Almost New Nocti". Now that's my reasoning. The summilux 75 would then be in my sights but it's a little tighter than I want and then I'd have to shift the 75 Summicron €1700 - 1800'ish and pick up the 75 Lux for €1500'ish, leaving €1200 in the pocket to help finance GAS clinic treatment.

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[Eoin]

So what 1.0 lens is supposed to be better - with the Noctilux you buy the best - and the worst. Doesn't do anything for me either, I agree, Guy.

 

LOL, not many f:/1.0 out there, I'd at least expect to be able to focus it correctly and have the image recorded in focus. A problem a few people seem to be having lately. So ........ I'd expect it to work.

[carstenw]

Eoin, what about a 50 Summilux, pre-Asph? It is meant to have a similar design and look to the 75 Lux, and is definitely softer wide open than a 50 Cron. The Noctilux is neat, but the bokeh often looks strained and weird.

 

Be careful with buying and selling a Noctilux. I had the same idea, but I have been firmly watching the sales of Nocts on eBay, and the highest prices I have seen have been around €2500-3000. I think it will be really hard to move a Noctilux at even €3500, never mind the new list price.