Lens Comparisons (old and new)

[Kevin Childress]

Yesterday I shot a series of tests to compare two lenses to be used in my macro work. Initially I was only trying to compare perceived sharpness and 1:1 reproduction ratio (both are advertised as capable of 1:1) but the tests revealed a couple other characteristics that I found very interesting. All tests were shot on my D800. 

• Lens #1: Nikon AF-S DX Macro 85mm f/3.5: Purchased new in July, 1012.  I have a lot of experience with this lens in macro work and in general photography. Although not a 'gold ring' lens, I've always been happy with the image quality. Its perceptible to some chromatic aberration but I've always been able to clean that up where necessary during raw conversion. For the past several months I've used this lens as the main lens in my macro work with my 50mm AF-S f/1.8 (new in September, 2011) reversed onto the front. That lens combination gives me 1.7x reproduction ratio and I've been quite happy with the results all around. 
• Lens #2: Micro-NIKKOR Auto 55mm f/3.5 P C: This is a pre-AI lens and the serial number dates manufacture to 1973. Soon I will have this lens converted to AI but for the time being I can only mount this lens to my D800 or D7000 using the Nikon M2 adapter ring (the M2 ring that I have is also 1973 vintage).  The M2 adapter ring is a 27.5mm extension tube that is required to achieve 1:1 with this lens, which is just as well since that was part of my intended testing. I received this lens as a gift (attached to a beautiful 1975-edition of a Nikon Nirrormat FT2!) in mid-2014. I've read on at least 50 websites that this lens is supposed to be one of the sharpest that Nikon produced in that period. A few days ago I decided to try using this lens in my macro work - reversed onto the 85mm lens in place of my 50mm f/1.8 - but before I got that far I decided to test it stand-alone to see what I was dealing with. 
  

The comparisons below are screenshots showing results from the DX Macro 85mm f/3.5 on the left and with the Micro-NIKKOR Auto 55mm f/3.5 on the right. Please ignore the file names shown for the right-hand comparison; I mistakenly typed '50mm' when saving the files instead of '55mm'. The aperture shown at f/3.5 is also incorrect. Being this is a non-CPU lens, the EXIF only identifies the maximum aperture as I saved it to the camera's list of non-CPU lens profiles. I've long believed that I get the sharpest images from the 85mm lens at f/16 so for these initial tests that's the aperture used for both lenses. Of course I set the focus and distance-to-the-subject to be able to focus as close as I could to the front of the glass. The subject is an old, beat up plastic ruler.

1) 1:1 Reproduction Ratio:  As best as I can tell both lenses produce the same results in this department. I could only measure a 6-pixel difference between the two and its quite possible that even the slightest difference in my manual focusing could account for the difference. 

2) Image Sharpness: The early tests clearly show the 2011 year model Macro 85mm f/3.5 has the advantage here. The results were consistent all across both frames but here I chose to use a 2:1 view to illustrate the differences. Both images below show very fine scratches in the plastic ruler. Its possible the 1973 year model Micro-NIKKOR Auto 55mm f/3.5 could produce sharper images at a different aperture but this is what I get at f/16. I'll be looking at this closer as I continue using the lens but for now this is the sharpest I was capable of focusing the lens.

3) Vignetting: This was actually a very pleasant surprise with the Micro-NIKKOR Auto 55mm f/3.5. Clearly the 55mm lens doesn't show the heavy corner vignette as with the 85mm lens. Rather it shows a very softly graduated vignette that I find quite pleasing. I'd be hard pressed to make any vignette 'corrections' with the Micro-NIKKOR Auto 55mm. 

4) Chromatic Aberration: Given the high contrast of this subject I wasn't too surprised at the results from the 'new' 85mm macro lens. After all its not a nano-coated lens and this is consistent with what I've seen in the past. It sucks but at least I can remove that color fringing in raw conversion. What I find outstanding is the results from the old Micro-NIKKOR 55!  This copy of the lens carries a "C" designation which back in that day meant an 'improved lens coating process' compared to earlier models. Clearly the coating works, whatever it is.

And that's it for now. The next set of tests will be to reverse the Micro-NIKKOR Auto 55 as I've been doing with my 50mm f/1.8 to see what happens ...

[© Tom Cooper]

I'm not sure that a lens that is designed for macro will work better reversed.  My understanding is that reversing a lens is intended to improve performace where the sensor is normally supposed to be closer to the lens than the subject, but you will be focusing so close that the subject will be closer to the lens than the sensor (i.e. larger than life size with a typical lens).

 

A macro lens might work better reversed, but not necessarily.

 

Tom

[Kevin Childress]

© Tom Cooper wrote:

I'm not sure that a lens that is designed for macro will work better reversed.  My understanding is that reversing a lens is intended to improve performace where the sensor is normally supposed to be closer to the lens than the subject, but you will be focusing so close that the subject will be closer to the lens than the sensor (i.e. larger than life size with a typical lens).

You're senses serve you well, Tom. I finished another series of tests including the Micro-NIKKOR 55mm f/3.5 reversed on the 85mm f/3.5 macro. That combination worked except that the reversed lens, being only f/3.5 wide open, practically vignetted the entire frame. But to your point, I also shot the 85mm f/3.5 using the extension tube and with the Micro-NIKKOR 55mm f/3.5 reversed and this did not work. The closest working distance to focus was somewhere inside the glass so that's certainly a no-go. I'll be putting up the new tests soon ...

[Kevin Childress]

Lens Comparisons (old and new), Continued:

I continued my macro lens testing to document the capability of each lens standalone and in combination with whatever extension tube or reversed-lens technique I could use. I wanted to determine how each combination would increase magnification and how each of those compared in sharpness. The subject is the "2014" engraved on a US quarter. As a reminder, the angle of view in these images is equivalent to that of a 1.5x crop image sensor. The image comparisons below show progressive magnification and line up like this:

1. Nikon AF-S DX Macro 85mm f/3.5 (standalone)
2. Micro-NIKKOR Auto 55mm f/3.5 P C  +  27.5mm extension tube (as I mentioned before, this extension tube is required for this lens comparison at 1:1 reproduction ratio)
3. Nikon AF-S DX Macro 85mm f/3.5  +  27.5mm extension tube
   
4. Nikon AF-S DX Macro 85mm f/3.5  +  Micro-NIKKOR Auto 55mm f/3.5 P C  (reversed)
   
5. Nikon AF-S DX Macro 85mm f/3.5  +  Nikon 50mm AF-S f/1.8  (reversed)
   
6. Nikon AF-S DX Macro 85mm f/3.5  +  27.5mm extension tube  +  Nikon 50mm AF-S f/1.8  (reversed)
7. Nikon AF-S DX Macro 85mm f/3.5  +  27.5mm extension tube  +  Micro-NIKKOR Auto 55mm f/3.5 P C  (reversed) : But no image to show for this combination. The closest focus distance was somewhere inside the lens stackup so I wasn't able to focus on the subject at all. Too bad because I was really looking forward to seeing how this worked!
   

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Nikon AF-S DX Macro 85mm f/3.5 (standalone): This is 1:1 reproduction ratio and gives me 137mm minimum working distance. The image is relatively sharp and this is my baseline for comparing sharpness with the other tests. There is plenty of detail in the high-res file and the working distance is certainly very comfortable. But I'm trying to find a happy balance between working distance, magnification, and image quality, so there's more to compare ...

Micro-NIKKOR Auto 55mm f/3.5 P C  +  27.5mm extension tube: This cuts my minimum working distance to 56mm.  This is also 1:1 reproduction ratio so no advantage with magnification over the 85mm macro lens standalone. The image quality is good and the colors look nice enough but its just not as sharp as the baseline above so I'm not sure how often I'll be using this combination. This is the same results as I shared in the original post. 

Nikon AF-S DX Macro 85mm f/3.5  +  27.5mm extension tube: Minimum working distance increases to a comfortable 120mm and now we're getting somewhere with increased magnification at 1.32x reproduction ratio. Unfortunately I loose TTL metering with this extension tube but I only have to shoot a few more test frames to find the exposure. Image quality is still good but I'm having a very hard time determining if this is sharper than the baseline, but I think the baseline 85mm macro alone still holds a slight edge. I like this combination of working distance and magnification so I'll work with this some going forward and see if I can get a sharper image.

Nikon AF-S DX Macro 85mm f/3.5  +  Micro-NIKKOR Auto 55mm f/3.5 P C  (reversed): I was really looking forward to trying this combination and this image has the sharpest pixels by far, but clearly the results aren't going to work. Tom mentioned in a previous reply that I might have an issue trying to reverse a macro lens onto another macro lens. The problem here is the diaphragm vignettes almost all of the image sensor. If that isn't bad enough, the working distance was only 4mm which is very painful and I had to reduce the main lens magnification so much that it pretty much made the test worthless. So, the baseline image is still the baseline ...

Nikon AF-S DX Macro 85mm f/3.5  +  Nikon 50mm AF-S f/1.8  (reversed): Minimum working distance is 12mm. Magnification increases to 1.7x (yippee!).  I've been using this combination for macro work for several months and I've been very happy with the results. Although the working distance is rather tight I've gotten somewhat used to it and I've worked out a couple lighting solutions to accommodate the tight quarters. At this close distance I can see very well to focus and this is a pretty sharp image. For all of these comparisons I tried to use the engraving marks (grinder marks) within the '2014' text. I'm very happy with this result so this is the new baseline.

Nikon AF-S DX Macro 85mm f/3.5  +  27.5mm extension tube  +  Nikon 50mm AF-S f/1.8  (reversed): Working distance reduces to 8mm (ouch!). As for magnification, I need to sleep on it but I think this is 2.2x (which would be great!). Image quality is very good although I think the new baseline is slightly sharper. I'll definitely be working with this combination more to see if I can improve.

And that's all for now, folks. Thanks for tuning in. There's more to come ...

[David Humphreys]

On Thursday, August 13, 2015 at 11:48:40 PM UTC+1, Kevin Childress wrote:

Lens Comparisons (old and new), Continued:

Just wondering if you've considered using a teleconverter with your macro lenses ?
I have had some success with a 2x converter and my 105mm macro lens for live insect photos , but it might fall well short of your high standards.

[Kevin Childress]

There are several complicated formulas needed to calculate the magnification power involved in this test (and I don't do complicated formulas). And I am seeing a huge disagreement in a couple of these calculations compared to pixel-level measurements that I can measure in Photoshop. The highest magnification I saw in this test was with the 85mm macro lens  +  27.5mm extension tube  +  50mm (reversed).  When the 50mm lens is reversed it essentially becomes a very powerful 'close-up' filter with the power of 20 diopter. One formula I find consistent reference to tells me that a 20-power diopter has 6x magnification (and that's just the 50mm lens alone and not taking into account the magnification power of the 85mm macro lens and extension tube). 

Okay, stop. The measurements I'm taking in Photoshop don't come anywhere near 6x. When comparing the 1:1-size image to the image with highest magnification, I am consistently measuring between 3.46x and 3.49x difference magnification. For discussion sake, lets round it down to 3.4x difference. That's a long way from the 6x power the 20-diopter close-up filter (alone) is supposed to provide. I tend to believe what I can see and feel, and what I can see and feel are two images that can be measured rather precisely at the pixel level. What am I missing here?

And of course we need to throw in the 85mm macro lens and extension tube. That combination alone is supposed to provide 1.32x magnification. I am also consistently measuring between 1.32x and 1.36x difference in this lens/combo test. So again, for purposes of this discussion, I think we can round this down to 1.3x safely. 

So, theoretically speaking, what do you get when you combine 1.3x and 6x power?  Is this 6 x 1.3 = 7.8???

[Kevin Childress]

David Humphreys wrote:

Just wondering if you've considered using a teleconverter with your macro lenses ? I have had some success with a 2x converter and my 105mm macro lens for live insect photos , but it might fall well short of your high standards.

Yes - have definitely considered it. I have Nikon's 1.4x AF-S TC but it physically won't fit on my 85mm macro lens. The only lens I have that it fits is the 300 f/4 (which I bought them at the same time, to live together, forever, as a matched pair). 

 

[David Humphreys]

Right.
If you happen to be passing my way I'll let you borrow my 105mm and 2x for an hour or two for you to test :-)

http://static.panoramio.com/photos/original/122528876.jpg

[Kevin Childress]

David Humphreys wrote:

Right.
If you happen to be passing my way I'll let you borrow my 105mm and 2x for an hour or two for you to test :-)

HAHAHAHA!!  You've got a deal!