Meiji 4X vs. 50/2.8 El Nikkor

NikonUser · Post by **NikonUser** » Tue Jun 30, 2009 10:10 am

Recently bought this used lens on ebay, US $32.00.

Ran a comparison against a reversed 50/2.8 El-Nikkor enlarging lens @ f/6.7.
70 frames in each @ 0.05mm, frame long side= 6mm (=3.9x mag on my sensor).
At the full frame and image reduced to 800 px for web display there is not much difference in quality of images.

Selecting 800px crops from the original stack shows the El-Nikkor to be sharper.

A major problem, for me, is that the full frame image (6 mm longest side) is the smallest size I can get with the Meiji with my current setup (can of course get a slightly higher mag.) ; a larger fly head would be too big for this lens to capture.

With the El-Nikkor I can capture an object as large as 11 mm on the longest side and fill the frame with an object only 4mm on its longest side. This range is avery useful advantage over the 4x objective.

The Meiji gives an acceptable image at 4x.
Bottom line, El-Nikkor best; but for subjects up to about 6x4 mm the economically priced 4x objectives are worth considering

rjlittlefield · Post by **rjlittlefield** » Tue Jun 30, 2009 10:57 am

Great comparison!

What's the NA on that objective?

--Rik

NikonUser · Post by **NikonUser** » Tue Jun 30, 2009 3:25 pm

The El Nikkor is of course f/2.8 (not 2.4).

The Meiji 4x is 160mm tube length, 0.17 cover glass thickness, 0.1 NA

Rik:
How about a FAQ: Which lenses can be used, in a controlled environment, for magnification >1x? Can you give links to the lenses and perhaps examples of how they perform?

This post could be one of the examples.

ChrisR · Post by **ChrisR** » Tue Jun 30, 2009 4:34 pm

Wouldn't the El Nik be even better a bit wider than f6.7?
At 4x you're effectively (4 + 1)6.7 = f33.5 so seriously into diffraction territory, I think?

For the 4x, NA 0.1 scope lens itself (ie, compared with f2.8 ),
the "f" number is about
1/(2*0.1)*4/(4+1)
=f4
which of course becomes f20

In both cases, a point source will be splatting light over a spot on your sensor several pixels diameter. Could it be then, that the difference that's visible, is more due to the effective aperture than the quality of the glass? I don't know.

http://www.cambridgeincolour.com/tutori ... graphy.htm

How about a FAQ: Which lenses can be used, in a controlled environment, for magnification >1x?

For 'scope objectives, if I have it about right, all we have to consider, without getting esoteric, are:

Tube length (vs infinity optics)
Cover glass thickness/correction
NA
Working Distance
Whether the lens was designed for use with a correcting eyepiece
Field coverage
Magnification (focal length)
Lens coatings
Optical quality
Mounting thread

Simple, then

rjlittlefield · Post by **rjlittlefield** » Wed Jul 01, 2009 10:59 am

NikonUser wrote:How about a FAQ: Which lenses can be used, in a controlled environment, for magnification >1x? Can you give links to the lenses and perhaps examples of how they perform?

Sure, that is certainly a frequently asked question!

I'm not sure how the FAQ will develop, but we can certainly get one started.

--Rik

NikonUser · Post by **NikonUser** » Wed Jul 01, 2009 11:17 am

I'm not sure how the FAQ will develop, but we can certainly get one started.

--Rik

Hopefully people will tell what lens they use, give a link to an image of the lens and results obtained with it.

Seems like a more direct way than having to go through "Search" which can return a lot of "stuff" (I've nearly alwys found search to be inefficient to put it politely)

rjlittlefield · Post by **rjlittlefield** » Thu Jul 02, 2009 1:22 am

Taking more time to look at these images, the EL-Nikkor image seems a lot sharper than what I would expect.

NU, can you list for us what camera you're using, and what sharpening (if any) you applied to the images either before or after stacking (or both), and confirm that the EL Nikkor was set to f/6.7 on its adjustment ring?

Thanks,
--Rik

NikonUser · Post by **NikonUser** » Thu Jul 02, 2009 9:30 am

ChrisR wrote
"Wouldn't the El Nik be even better a bit wider than f6.7?
At 4x you're effectively (4 + 1)6.7 = f33.5 so seriously into diffraction territory, I think?"

From earlier tests and comments from other users (I believe Charles) 1/2 stop less than f/5.6 was reckoned to give the 'best' overall image for the El Nik 50/2.8. I translated this as f/6.7.
My basic criterion for choosing an f-stop is to choose the one that gives me the image I prefer. For this lens f5.6 and f/6.7 produce significantly better images than at f/4 and f/2.8.
Certainly debateable as to whether f/5.6 is better than f/6.7, but any difference is minor.
If f/6.7 is producing serious diffraction that's OK with me, it's the best I can get with this lens.

Sometimes theory gets it wrong. I remember that a bunch of engineers determined that a bumble bee could not fly - wrong design, too fat, wings too small.

NikonUser · Post by **NikonUser** » Thu Jul 02, 2009 10:26 am

rjlittlefield wrote:Taking more time to look at these images, the EL-Nikkor image seems a lot sharper than what I would expect.

NU, can you list for us what camera you're using, and what sharpening (if any) you applied to the images either before or after stacking (or both), and confirm that the EL Nikkor was set to f/6.7 on its adjustment ring?

Thanks,
--Rik

Rik:
D90, ISO 100, bellows, 50/2.8 El Nikkor; SB-800 flash, coffee cup diffuser.
68 frames @ 0.05mm ZS PMax stack.
No way to confirm f/stop was 6.7; only other reasonable stop would be f/2.8 as I focus with the lens wide open and then stop down to shoot. I don't record what image processing I do.
So, I'll go back to the original.
Below is the actual output from ZS using the fine small jpg frames directly from the camera (not sure what the camera did to get the jpgs). No sharpening, no processing.
Actual stacked image is 2144 x 1424 px.
This image is reduced to 800 px wide (Bicubic) and converted from Adobe RGB to sRGB.

Added: In the initial test I was comparing the 2 lenses. Whatever I did was to get the best final image I could from each. Thus I think the comparison is fair and the results are accurate.

rjlittlefield · Post by **rjlittlefield** » Thu Jul 02, 2009 2:42 pm

NikonUser wrote:Whatever I did was to get the best final image I could from each. Thus I think the comparison is fair and the results are accurate.

I understand and I agree with that philosophy for direct lens-to-lens comparisons.

I'm just trying to make sense out of observation versus prediction, particularly the issue that ChrisR raised about being "seriously into diffraction territory".

One of the handwaving rationales I've used for a long time has been that proper sharpening can essentially flatten out the tail of the MTF curve that would otherwise slope off from diffraction blurring. Sharpening can't change the cutoff frequency, but it can make visible detail that would otherwise be lost in the blur. Or so goes the argument.

I notice that even the full frame unsharpened image you're showing here at 800 pixels looks a lot less sharp than the corresponding image in the first post.

Can I get you to show us an actual-pixels crop of the unsharpened frame, that we can compare against the actual-pixels crop of the sharpened image in the first post?

I have a funny feeling that it's going to make a great case for sharpening.

--Rik

NikonUser · Post by **NikonUser** » Fri Jul 03, 2009 3:54 am

Here is the complete ZS output from the jpg frames actual pixels (cropped out some empty space, but no other adjustments).
Hopefully your can fit the 4 bits together to get a full-sized actual pixel image.
Why don't you play around with sharpening and see what you can come up with.

ChrisR · Post by **ChrisR** » Fri Jul 03, 2009 5:54 am

Yes they go together fine, but when looking at the hairs, the jpeg artifacts get in the way. I assume that happens when the image is posted to PM, rather than what comes out of ZS.
Sharpening this:

isn't pretty

.

Would uploaded gif files look better? Might hit the 200k? limit?

NikonUser · Post by **NikonUser** » Fri Jul 03, 2009 6:20 am

Chris:
The original individual frames are in both fine small jpg (causing the un-prettiness here) and RAW (NEF) files. Unfortunately ZS can't handle RAW. Helicon Focus can but it tends to put halos around hairs. Guess I could convert the RAW files to large high quality JPGs or TIFs and then run ZS - but that's a lot of work!

ChrisR · Post by **ChrisR** » Fri Jul 03, 2009 7:11 am

It never occured to me to use anything other than raw or fine large jpeg - something to check

.

I know I'm laboring the point - but does this forum compress image files to poorer quality jpegs? I wonder if that's where the boxy shapes come from?
Let's see

This doodle has never been a jpg, uploaded from a gif:

Nope, copied from the forum and pasted back in to Photoshop and blown up, no jpeggery pokery build up.

NikonUser · Post by **NikonUser** » Fri Jul 03, 2009 7:28 am

Rik and I had this discussion a while back. I was working with fine large JPGs from a D2Xs and it was taking ZS eons to process (not quite true, but way too long). Consensus was that my incredibly expensive 3-yr Dell was a piece of c**p. Rik recomended using small JPGs for images to be posted on this site. Seemed to work OK, except when someone starts "pixel peeping".

Added: The problem as I see it: the image was taken for a specific purpose and it is being used for another purpose for which it is not suitable. Surely to test theory images should be taken specifically for that purpose. I could easily take some images of fly hairs or eye facets (at f/4, f/5.6, f/6.7, f/8) using highest quality large JPGs or even TIFs (D2Xs records TIFs, D90 does not).