Threes. A crowd.

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ChrisR
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Threes. A crowd.

Post by ChrisR »

Recently folk have been asking how to better their El-Nikkor 50mm f/2.8, reversed on bellows.
I decided 3x would be appropriate. Much less and it's out of its comfort zone, much more and diffraction fuzzies everything.

As I seem to have accumulated enough ways to get 3x to try one a day until Christmas, I thought I'd have a go. What I suspected, was that it would be beatable, but not enough to get really excited about.
Some of the results, I'm looking forward to, such as an infinite 2x NA 0.1 objective on a Canon 300L zoom, or an infinite 4x NA 0.2 on a 135mm tube lens (=2.7x). But those will have to wait.
Here's the first four.
One of them's the Nikkor, the other three aren't. I don't have the notes handy, so try guessing ( :twisted: :lol: ). What order would you put them in?
Steps are too fine so as not to lose anything, about 20u. (I only did 4 because at 2am I was tired - then the batch was still running when I got up..)
100% pixels, Dmap, flash + fairy cake diffuser, lens "hood", optimum aperture where settable, no in-camera or post tweaking.
The second image is a little too light, sorry.
Canon D600 (18Mpixel), 100ISO, Red Admiral, strange white deposit.
All from jpegs, not via raw - something else to try.
Here's the field, red rectangle section marked:
Image
And four results
Image

(Christmas 2012, by the way
Bear in mind you mind you might be looking at a Luminar, Minolta, Mitutoyo, reversed Micro Nikkor, reversed 50mm planar on a prime, Milar, Olympus 50, 80, 38/2.8 or 3.5, Schneider, Rodenstock, Wray Supar etc)

canonian
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Re: Threes. A crowd.

Post by canonian »

ChrisR wrote:... What order would you put them in?...
No idea, is the third one the Nikkor?
Interesting tests coming up, can't hardly wait until Xmas 2012. :)

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Post by ChrisRaper »

Hmm, I dislike #1 and #3 (they seem a bit too fuzzy) so I think those are poorer quality lenses. #2 and #4 are harder to split but I might go for #2 as being the best of the 4.

My own tests don't look too shabby compared to these so I am fairly happy that my EL-Nikkor 50mm f2.8 is performing within acceptable tolerances :)

I'm really interested to see the final results - thanks for taking the time to do this work. Ultimately it would be nice if other forum members could also post similar tests with their own lenses and collate all of these together, to eliminate variation between individual lenses :)

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Post by ChrisR »

One obvious contender I don't posess, is the Canon MPE-65.
Can anyone remember a sample image of a similar subject at the same magnification?

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Post by ChrisRaper »

ChrisR wrote:One obvious contender I don't posess, is the Canon MPE-65.
Can anyone remember a sample image of a similar subject at the same magnification?
There are some similar images on this web-page but I'm not sure whether they are a fair comparison. :)

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Post by ChrisR »

That shows quite well how any comparison has to use the same subject, lighting etc. That would probably apply even if the same reference lens is included for comparison. Without a reference I don't think we can tell too much.

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Post by curt0909 »

Nicely done comparison. #2 looks best. 3,4 look almost even and 1 looks worst. I have a 1st generation nikkor 50mm 2.8 and I'm happy with the results.

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Post by rjlittlefield »

ChrisRaper wrote:Hmm, I dislike #1 and #3 (they seem a bit too fuzzy)
This test and ChrisRaper's evaluation raise some interesting points that I haven't seen discussed before.

Consider the following:

Image

This is the top middle section of ChrisR's image, pulled off my browser as a screen capture so you can be sure what I'm looking at.

At the top and middle arrows, the brown scales are much better on the left.

But at the bottom arrow, the white fleck is about the same on both sides, and actually I see it as a hair better on the right.

Looking around the frame, the same pattern seems to hold for other brown scales and for other white flakes.

So I'm left thinking that if the test subject were entirely brown or entirely gray, we would get very different impressions of how the lenses compare.

Any idea what's going on? Any independent test results to substantiate that idea?

--Rik

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Post by ChrisR »

Hmm, as a Welshman would say, "There's curious for you."
I did wonder whether I would be sworn at, (offlline of sourse!) for not saying what the lenses were, but I'm glad I didn't.
How easy it would be, to make the facts of the image fit the accepted notion of how the lens ought to behave! Having one or other in one's possession usually increases its assumed worth, even if only to support the owner's buying decision. Unless, say, the aperture ring doesn't feel right between the fingers - then you always knew it wasn't great..

Some thoughts:
The brightness does vary a little. If you darken lens #2's image, the reds get much redder, but the flary-whites are reined in.
I might have moved the diffuser differently while changing lenses.
I can see JPEG edges if I look close - I'll convert from raw to tiff to avoid that.
To me, #3 (the right of Rik's two) looks more grainy - how can that be?
They aren't radically different lenses, they're both enlarger lenses reversed.

Question for Rik- these are Dmap, default settings. If the "best" apertures which I chose , and therefor the step sizes, were slightly different, would that of itself alter the way the graininess/noise/flary whites, come out?

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Post by rjlittlefield »

ChrisR wrote:Question for Rik- these are Dmap, default settings. If the "best" apertures which I chose , and therefor the step sizes, were slightly different, would that of itself alter the way the graininess/noise/flary whites, come out?
I don't see why any of those would be affected.

With DMap, there's always the possibility that best focus can get missed at any particular position, but generally that's a random thing and in this case the brown edges seem to be consistently sharper on the left. I can find a couple of brown edges that are roughly the same, lots that are sharper on the left, and none that are sharper on the right.

Going back to the original source images would tell more of the story. Can you poke through the full stacks, find the best-focused single frames at representative positions, and show us those?

--Rik

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Post by ChrisR »

I think part of it, looking at the single frames, is a variation in brightness between exposures.. Surprising perhaps at 1/32nd flash.
But I'm still looking at jpegs I don't trust ... back later!

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Post by ChrisRaper »

So, when do we get the "answer" to which is the EL-Nikkor? Or do you want to draw out the torture for a few days more? ;)

Personally, I think the similarity of #2, #3 & #4 at least shows that there are some very comparably good lenses out there in the 3:1 range ... I just hope that they're also the cheap ones so that I can add them to my "eBay wants" list :D

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Post by ChrisLilley »

For me it is #2, then #3, with #1 and #4 joint third place being smeary and dull. I wondered if was seeing more in #2 just because its a dark area of the subject and is exposed a bit lighter than the others. But it seems crisper with better contrast and definition overall and the colours look cleaner, somehow.

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Post by ChrisR »

This has been driving me mildly nuts for a few hours now, trying to see "what's going on between the lines", so to speak.

Even knowing to begin with which lens was which, after trying to make the best of each one I soon forgot. Once "normalised" by experiment ( I have nor standardised method for doing that) they look much more similar to each other.
I depends what you look at across the frame, very much. Then adjustments to Curves transform the whole image. Sharpening does, too. Using a large radius (perhaps 25 pixels) and a low level perhaps 20%, removes foggy haloes and does wonders for contrast. It can make the whites too bright, so hold them down a bit first.
Yes those scales in #3 do look rather turgid, but elsewhere it's about the best. Even lens#1 looks fine in many areas - the white blob Rik pointed to is probably the sharpest. Even when darkened, #2 still leaves the white particles glowing.
What's more, in a couple of cases I have more than one of them, and they do vary.

I found that some frames were a little darker than the average, and it made a difference. Those dull scales in #3 are a case in point. It's not much but it has made a difference.
One partial solution to that is to overlap the steps more. If there's a 50% overlap, every sharp pixel gets exposed twice.

Looking really closely, a difference can be seen between the Jpeg-from-camera stacks and the raw>tiff stacks, If the "artefact" from a jpeg box-edge happens to run through a lobe on a scale, tough, it'll show. This would be camera sensor/software dependent. I haven't noticed it with a Nikon D700. (That can also spit out tiffs, though I hadn't realised they're only 8 bit)

Image

Image

to be edited.....

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Post by Oskar O »

I noticed the same thing as Rik did. To me, the best depends on which part of the image I'm looking at.

I would be hesitant to make too many conclusions out of jpegs. First, the brightness of the images vary and second, jpeg favors luminance over chrominance, giving red areas particularly poor definition. The slight changes in brightness and contrast, combined with the fairly pure reds could lead to undesired artifacts. Just sayin...

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