Nikon 500mm f4 G vs 300mm f4 pf sharpness

[jjd291]

Hi All! Gear question here, having mystery sharpness problems common to many on photography discussion boards but I’d like to think I’ve crossed off most of the main contenders!

I purchased my Nikon 500mm f4 G lens from a well known used camera shop in the UK around a year ago, and have never really been happy with the sharpness. Wide open, both the contrast and sharpness is lacking significantly, improving at f5.6 and hitting a sweet spot at f8 with image quality I’m satisfied with on crop sensor and high mp bodies.

At first I assumed that it was my technique was lacking, having previously used shorter focal length lenses for my wildlife photography (300mm f2.8 VR II, 200-400mm f4 VR). Once I was sure I had my technique locked down and the issue wasn’t eliminated, I moved on to looking at focusing issues. I fine-tuned the lens with and without tc using lensalign which made little difference. I shoot a lot on rocky, wet intertidal zones so I hoped the issue was one of heat haze cropping up at shorter than normal distances due to the extreme temperature differentials. I checked this out in more controlled conditions and the results were the same. I use a large, stable carbon fibre tripod with a 40kg max load and either a fluid video head or gimbal, and I don’t think it’s a support issue.

All of this came to a head when I bought a 300mm f4 pf lens recently as a walkabout lens. I had accepted that maybe I had too high expectations for an older supertelephoto, and I had seen a few cases of people claiming that the lens wasn’t all it’s cracked up to be on modern high megapixel sensors. I sold my d850 before Christmas and managed to find a used d5 for a steal, hoping that the extra iso performance and more forgiving megapixel count would enable me to shoot the lens consistently stopped down on overcast days (I photograph birds and mammals in a particularly rainy, damp part of the uk). When the 300mm arrived, I used it exclusively for a few weeks to get used to it and was very impressed by the sharpness wide open, even with a 1.4x teleconverter. To my surprise, photos taken with the pf and teleconverter exceeded those taken with my bare 500mm lens!

I’ve attached three photos, each 100% jpeg crops from an unedited d7500 raw file with base 40+ sharpening applied in Lightroom. I took three photos with the 500mm f4, 300mm pf and 300mm pf + tc14iii and chose the sharpest from each (excuse my poor methodology). I really gave the 500mm every chance as I shot the photos as I would using each lens in the field to make the test results more relevant to me - 500mm f4 on the locked down tripod with live view, no VR and timer, the pf lens handheld with VR on in both instances.

Settings were as follows: 1/320 sec, wide open for each combo (f4/f5.6), iso 400,450,720 respectively.

500mm f4 G

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300mm f4 pf

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300mm f4 pf with 1.4 tc14-e III

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To my eye, there is clearly a massive difference in both sharpness and contrast between the two lenses. I’m at a loss for what to do next other than send the 500mm f4 to Nikon, although as it’s out of warranty any repairs will add up fast and due to the plummeting value of f mount fast glass and my uni fees, that’s not a very economical option for me and therefore a last resort. There appears to be a significant amount of dust in the lens, but I don’t believe this would affect sharpness, only contrast if at all. Has anyone switched from the supertelephoto G lenses to more recent f mount glass and experienced the same thing, or seen the same issue with their lens? The MTF lines of both lenses don’t suggest the issue I’m having at all but I know that’s not the whole story. Open to any ideas or suggestions, I know my testing methodology was poor but I've experienced this consistently with the lens and I've owned a 300mm f2.8 and 200-400mm f4 so I know what good (and sometimes bad!) glass can produce!

 

[Steve W]

To me, the top photo looks like nothing is truly in focus.

 

[NorthernFocus]

The 500 f4G should be able to outperform the 300PF. Or at least match it. Particularly stopped down to 5.6. I owned them both. You mention that there is dust visible in the lens. It it fine powder looking material or larger particles? If it is very fine it may be mold and if so could certainly cause problems.

BTW hopefully for your fine tuning you picked a better target than what you posted here. A flat target with high contrast lines/patterns/text lends itself to objective comparison.

 

[jjd291]

To me, the top photo looks like nothing is truly in focus.

Yes it’s quite odd, I get the same result with normal af, focusing in live view and manual focusing. When manual focusing and viewing at 200% in live view it almost seems to breath in and out of focus slightly despite being locked down and experiencing no vibrations.

 

[jjd291]

The 500 f4G should be able to outperform the 300PF. Or at least match it. Particularly stopped down to 5.6. I owned them both. You mention that there is dust visible in the lens. It it fine powder looking material or larger particles? If it is very fine it may be mold and if so could certainly cause problems.

BTW hopefully for your fine tuning you picked a better target than what you posted here. A flat target with high contrast lines/patterns/text lends itself to objective comparison.

That’s good to hear thank you, nice to know I’m not going crazy! The dust is a fine powder that seems partially reflective, I’ve attached a photo below. I can’t see any etching patterns on the glass as one would expect with fungus, but I’m no expert.




The 500mm f4 was fine tuned using a lens align set up and gave a result of around -5, with the 300mm perfect out of the box and needing -10 with tc. I’ve experienced the issue shooting in live view, which if I understand correctly demonstrates that the issue isn’t one of fine tuning? I can try and replicate the same examples with an indoor setup but this isn’t something I have the space to do easily in my flat, if it can shed some light on this I’ll give it a try though.

 

[NorthernFocus]

Oh for goodness sake. With that much particulate matter in the lens it's no wonder. You're wasting time.

 

[Krümelkraft]

I somehow have the impression that the 500 lens is not correctly focused. Look at the wood on the right: It seems sharper than on the 300 image. On the 300 image, the wood is clearly out of DOF, the center is sharp. With the 500 properly focused, I would expect the wood stick at least as unsharp as in the 300 image.

You can check this by shooting the target with an angle. If the lens is sharp but defocused, you will see maximum sharpness somewhere in the image (maybe not in the middle, where it should be). If the region of maximum sharpness is still softer then the 300, then there might be something wrong with your lens.

Also try shooting the 500 handheld with high shutter speed, with good light outdoors. Tripods can cause small but high-frequency vibrations due to elastic moments.

What was the distance of the shots? (Lenses tend to be soft close to the minimum focusing distance)

Ok, after seeing your dust image, I wouldn't rule out that it's a dust effect. It's really a lot.

Also note that fine tuning can go wrong.

 

[jjd291]

Oh for goodness sake. With that much particulate matter in the lens it's no wonder. You're wasting time.

I was under the impression that dust at the objective end of the lens wouldn’t impact sharpness to that extent, only contrast if anything, and when I bought the lens the company claimed that the dust had no effect on image quality.
I’ll certainly send it in for a CLA if you think that’s the culprit, it’s quite hard to find much concrete evidence of dust impact on lenses beyond surface level observations online so I took the dealer’s word on it. Thanks for your input!

 

[jjd291]

I somehow have the impression that the 500 lens is not correctly focused. Look at the wood on the right: It seems sharper than on the 300 image. On the 300 image, the wood is clearly out of DOF, the center is sharp. With the 500 properly focused, I would expect the wood stick at least as unsharp as in the 300 image.

You can check this by shooting the target with an angle. If the lens is sharp but defocused, you will see maximum sharpness somewhere in the image (maybe not in the middle, where it should be). If the region of maximum sharpness is still softer then the 300, then there might be something wrong with your lens.

Also try shooting the 500 handheld with high shutter speed, with good light outdoors. Tripods can cause small but high-frequency vibrations due to elastic moments.

What was the distance of the shots? (Lenses tend to be soft close to the minimum focusing distance)

Ok, after seeing your dust image, I wouldn't rule out that it's a dust effect. It's really a lot.

Also note that fine tuning can go wrong.

Thanks for your reply! I think the focus on the wood to the right is likely a fault of my testing methodology, I handheld the 300mm at an approximately similar fov as I would be compensating for a lack of reach by moving my feet in the field.

I’ll definitely check that thanks . I’ve encountered the same problem handheld at high shutter speeds unfortunately. Shots were taken around 6 meters so fairly near the mfd.

It looks like the lens is going off for a CLA with two votes for dust, thanks for your help!

 

[NorthernFocus]

1) It's true that small amounts of dust inthe objective end won't "significantly" affect IQ. This is excessive

2)There's no way to tell if the same amount of dust is also deeper in the lens.

3) If you don't think it affects sharpness try shooting your sharpest lens through a screen door and see what you think.

BTW if it doesn't matter why do any of us bother cleaning our lenses. And why are we willing to pay a premium for fluorite coating that repels dust and water?

Horse led to water...

 

[jjd291]

1) It's true that small amounts of dust inthe objective end won't "significantly" affect IQ. This is excessive

2)There's no way to tell if the same amount of dust is also deeper in the lens.

3) If you don't think it affects sharpness try shooting your sharpest lens through a screen door and see what you think.

BTW if it doesn't matter why do any of us bother cleaning our lenses. And why are we willing to pay a premium for fluorite coating that repels dust and water?

Horse led to water...

I can’t see dust deeper in the lens but I’m not discounting it. I don’t doubt that there will be some impact, as I said there is scant evidence for the impact of this level of dust online.

I think you’re under the impression that I didn’t take your advice seriously or appreciate it, which isn’t the case. I certainly didn’t say that lens care doesn’t matter, the lens was in this condition when purchased and I was relying on the shop’s information. I store my equipment carefully and since the consensus is that this level of lens dust impact sharpness, it will be sent in for a CLA to remove the dust .

 

[SCoombs]

I'm no expert, but I always remember being struck by a video where a photographer took a lens and destroyed the front element (on purpose) by very badly scratching it up with a rock, even taking chips of glass out of it if I recall, to then demonstrate that there was no especially noticeable decrease in the image quality.

 

[jjd291]

I'm no expert, but I always remember being struck by a video where a photographer took a lens and destroyed the front element (on purpose) by very badly scratching it up with a rock, even taking chips of glass out of it if I recall, to then demonstrate that there was no especially noticeable decrease in the image quality.

I think I remember the same video! I’ve been judging the impact of dust by a dpreview video looking at the impact of dust and scratches on contrast and sharpness. I don’t take one persons opinion as gospel, but by their findings it would seem that wide open telephoto lenses are the least vulnerable to heavy dust and debris.

I’m not quite sure why stopping down increased sharpness significantly on my copy, when it seems to me the opposite would be true for a lens full of dust and debris. Maybe there are some evaporated lubricants on the glass, it looks like I’ll find out when it joins the long waitlist for CLA and repairs in the UK!

 

[SCoombs]

I think I remember the same video! I’ve been judging the impact of dust by a dpreview video looking at the impact of dust and scratches on contrast and sharpness. I don’t take one persons opinion as gospel, but by their findings it would seem that wide open telephoto lenses are the least vulnerable to heavy dust and debris.

I’m not quite sure why stopping down increased sharpness significantly on my copy, when it seems to me the opposite would be true for a lens full of dust and debris. Maybe there are some evaporated lubricants on the glass, it looks like I’ll find out when it joins the long waitlist for CLA and repairs in the UK!

Well obviously stopping down usually increases sharpness because of optics, so I think that either the dust isn't really the culprit OR, maybe more likely, the dust isn't the ONLY culprit and when stopping down there is a balance between how much it is bringing the dust more into the picture and how much it is helping the optics of rhe overall lens.

 

[MrFotoFool]

I briefly owned the 300 PF that I bought used. The bare lens was fine but with the 1.4x iii teleconverter the results were unacceptable to the point that the teleconverter was unusable. (Others have reported better results so maybe it was my copy). I know the teleconverter itself was good because I had been using it with my 70-200 f2.8 E and the results were outstanding.

 

[jjd291]

I briefly owned the 300 PF that I bought used. The bare lens was fine but with the 1.4x iii teleconverter the results were unacceptable to the point that the teleconverter was unusable. (Others have reported better results so maybe it was my copy). I know the teleconverter itself was good because I had been using it with my 70-200 f2.8 E and the results were outstanding.

That definitely sounds like an iffy copy to me, bad luck! I’m normally not a big teleconverter user as I don’t like adding more variables to image quality, but I have to say that the tc-14iii on the 300mm pf has absolutely blown me away. I think it’ll end up practically glued to the lens! Did you try fine tuning?

 

[steeves]

that amount of dust internally basically acts like a diffusion filter. I would get it cleaned.