c h u n k
Senior Member
I find this really hard to believe. Would you mind sharing images with those results with settings. I am NOT calling you a liar so please dont take it like that. I just think there is another explanation.
-
Welcome to the new forums! Please read this first. For known issues we are working to resolve, click here.
Achromat close-up lens gives worse results than extension tube - why?
- Thread starter Egg Salad
- Start date
Egg Salad
Well-known member
I can't upload anything today, but I'll hopefully get to that tomorrow.
I'll also comment on the other posts then.
John K
Forum Pro
I'm not convinced that apparent aperture has anything to do with diffraction, it's just a way of adjusting for the very small surface area that's reflecting light back into the lens at 1x and higher mag (so used for calculating exposure). There should be no difference in the diffraction softening at F11 with a lens set to 1:2 or 1:1 -the physical size of the aperture doesn't change when you turn the focus ring on a lens...
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
--
Also known as Dalantech
My Book: http://nocroppingzone.blogspot.com/2010/01/extreme-macro-art-of-patience.html
My Blog: http://www.extrememacro.com
My gallery: http://www.johnkimbler.com
Macro Tutorials: http://dalantech.deviantart.com/gallery/4122501/Tutorials
Always minimal post processing and no cropping -unless you count the viewfinder...
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
--
Also known as Dalantech
My Book: http://nocroppingzone.blogspot.com/2010/01/extreme-macro-art-of-patience.html
My Blog: http://www.extrememacro.com
My gallery: http://www.johnkimbler.com
Macro Tutorials: http://dalantech.deviantart.com/gallery/4122501/Tutorials
Always minimal post processing and no cropping -unless you count the viewfinder...
Last edited:
filmluvr
Senior Member
I have only too recently abandoned the idea of not fully stopping down. There are plenty of examples online to indicate that apertures of f/22 and f/32 are just fine for this work (at least with full frame, which is what I shoot). Funny, I haven't read anything regarding the possible effects of mirror bounce in this genre. Maybe the short flash duration eliminates this issue.I'm not convinced that apparent aperture has anything to do with diffraction, it's just a way of adjusting for the very small surface area that's reflecting light back into the lens at 1x and higher mag (so used for calculating exposure). There should be no difference in the diffraction softening at F11 with a lens set to 1:2 or 1:1 -the physical size of the aperture doesn't change when you turn the focus ring on a lens...
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
Jack
--
John K
Forum Pro
I know of several macro shooters that are setting their lenses to F22 and there's plenty of detail. The MP-E 65mm has a maximum Fstop of 16, and it's perfectly acceptable at 2x mag, and I've shot up to 5x with good results:
Tech Specs: Canon 70D (F16, 1/250, ISO 100) + a Canon MP-E 65mm macro lens (@5x) + a diffused MT-24EX (both flash heads on Kaiser adjustable flash shoes). This is a single, uncropped, frame taken hand held.
Mirror bounce is only an issue if you have the camera on a tripod, because there's a single point holding the camera. But then again vibration due to wind is also an issue, and I never see anyone weighing down their tripod.
When hand holding a camera mirror slap probably doesn't cause any problems because the camera is being stabilized at two points. I'm typically holding the camera grip with my right hand, and bracing the lens on my left. So minor vibration shouldn't be an issue.
--
Also known as Dalantech
My Book: http://nocroppingzone.blogspot.com/2010/01/extreme-macro-art-of-patience.html
My Blog: http://www.extrememacro.com
My gallery: http://www.johnkimbler.com
Macro Tutorials: http://dalantech.deviantart.com/gallery/4122501/Tutorials
Always minimal post processing and no cropping -unless you count the viewfinder...
Egg Salad
Well-known member
I think I wrote it before. The comparison was done at around 1:3. At this magnification, f/3.5 is an aperture that I might even use in the field. At 1:3 I hardly ever stop down further than f/8.
Even at 1:1 I don't use apertures smaller than f/13. I find the massive drop in resolution a bigger issue than the tiny depth of field. I always wanted to try focus stacking, but never found the patience and software.
Egg Salad
Well-known member
Since I couldn't test those claims without owning the lens(es) myself, there was no way knowing whether or not if was true. Turns out it's mostly true.
"Require" is too big a word. It's more about my standards. When out of the lenses I have one of them gives the best results, I cling to that performance.
What makes this difficult is that this said lens may not be as good in other areas, making it hard for me to decide which I should keep.
I applaud you on being steady enough to hit the focus plane on your shot!
Egg Salad
Well-known member
I repeated my tests. This time shooting at f/2, f/4 and f/8. For lenses slower than f/2 only f/4 and f/8. I'll only show f/4 and f/8. The lighting was very inconsistent withvarying cloudiness, so ignore differences in brightness and WB.
The comparison was done around 1:3 and 1:1,625.
1:3 magnification
Sigma 50/1.4:
the Marumi retains more detail than the extension ring, especially in the edges and at bigger apertures. Center resolultion is similar.
f/4, +10mm extension
f/8, +10mm extension
f/4, +Marumi +3
f/8, +Marumi +3
Tamron 70-200:
clear win for the Marumi. Everything looks better.
Note: magnification only reached 1:3,2 with tubes.
f/4, 200mm, +16mm extension
f/8, 200mm, 16mm extension
f/4, 103mm, +Marumi +3
f/8, 103mm, +Marumi +3
Sigma 135/1.8:
at f/2 the Marumi produces a hazy mess, image with extension ring looks useable. Huge boost in contrast at f/4 for the Marumi, but resolution never reaches the tube's resolution level, not even at f/8.
f/4, +16mm extension
f/8, +16mm extension
Note: minimal magnification is 1:2,5 with the Marumi
f/4, +Marumi +3
f/8, +Marumi +3
Macro lenses for reference:
Zeiss 50/2:
strong vignetting, very even sharpness across the frame with high contrast.
f/4
f/8
Sigma 105/2.8:
maybe slightly weaker corners than the Zeiss, lower contrast.
f/4
f/8
Overall result:
At 1:3 the Sigma 50/1.4 + Marumi and Sigma 135/1.8 +16mm are equal at all tested apertures and very close to the macro lenses in the center. The Tamron 70-200 + Marumi is good in the center but can't keep up in the corners - which is within expectations.
For high edge sharpness from wide open, the dedicated macro lenses remain unbeaten.
Last edited:
Egg Salad
Well-known member
1:1,625 magnification (maximum for the Tamron 70-200)
Tamron 70-200:
image is still hazy at f/4, reaches pretty good sharpness at f/8.
f/4, 200mm, +Marumi +3
f/8, 200mm, +Marumi +3
Sigma 135/1.8:
image somewhat hazy at f/4 but much better than the Tamron 70-200.
f/4, +Marumi +3
f/8, +Marumi +3
Sigma 105/2.8 for reference:
f/4
f/8
Overall result:
At 1:1,625, the Sigma 135/1.8 gets vey close to the Sigma 105/2.8 stopped down to f/8 and might even surpass it in the center, but in the edges, the macro lens stays clearly ahead.
Tamron 70-200:
image is still hazy at f/4, reaches pretty good sharpness at f/8.
f/4, 200mm, +Marumi +3
f/8, 200mm, +Marumi +3
Sigma 135/1.8:
image somewhat hazy at f/4 but much better than the Tamron 70-200.
f/4, +Marumi +3
f/8, +Marumi +3
Sigma 105/2.8 for reference:
f/4
f/8
Overall result:
At 1:1,625, the Sigma 135/1.8 gets vey close to the Sigma 105/2.8 stopped down to f/8 and might even surpass it in the center, but in the edges, the macro lens stays clearly ahead.
Last edited:
Egg Salad
Well-known member
Proof that extension rings negatively affect image quality:
1st image is with the naked Zeiss 50/2, 2nd image is with the Zeiss 50/2 +10mm extension, focused in a way that it offers the same magnification (~1:2.5).
f/2
f/2 +10mm extension
At f/5.6 the output with extension ring has hugely improved, but still lokks worse than with the naked lens.
BTW: this is why performance at f/3.5 is field relevant to me.
1st image is with the naked Zeiss 50/2, 2nd image is with the Zeiss 50/2 +10mm extension, focused in a way that it offers the same magnification (~1:2.5).
f/2
f/2 +10mm extension
At f/5.6 the output with extension ring has hugely improved, but still lokks worse than with the naked lens.
BTW: this is why performance at f/3.5 is field relevant to me.
c h u n k
Senior Member
I'm not convinced that apparent aperture has anything to do with diffraction, it's just a way of adjusting for the very small surface area that's reflecting light back into the lens at 1x and higher mag (so used for calculating exposure). There should be no difference in the diffraction softening at F11 with a lens set to 1:2 or 1:1 -the physical size of the aperture doesn't change when you turn the focus ring on a lens...
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
gardenersassistant
Veteran Member
My Panasonic and Sony cameras don't report the effective f-stop; the reported f-stop is constant independent of magnification.Effective f-stop is, for all intents and purposes, the f-stop. Other cameras actually register the fstop. Canon is kind of unique for not having it reflect in the settings.I'm not convinced that apparent aperture has anything to do with diffraction, it's just a way of adjusting for the very small surface area that's reflecting light back into the lens at 1x and higher mag (so used for calculating exposure). There should be no difference in the diffraction softening at F11 with a lens set to 1:2 or 1:1 -the physical size of the aperture doesn't change when you turn the focus ring on a lens...
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
John K
Forum Pro
I wanna address a few things in your post, since you seem to be either making assumptions or putting words in my mouth. As someone who shoots single frames at high mag I understand diffraction better than most. The problem isn't that the light is bending as it's passing through the aperture, it's that the rays are spreading out into a cone. Noticeable diffraction is defined as light rays spreading out so that they fall half way into adjacent pixels. So sensors that have gaps between the pixels are less diffraction prone because a lot of diffracted light doesn't get recorded (bleeds into the gaps) and sensors with gap-less micro-lenses are more diffraction prone (no spaces to hide diffracted light). So the physical makeup of the sensor plays a roll in how much diffraction is recorded...
But notice how none of that has anything to do with effective aperture, because the physical aperture of the lens is all that really matters. So why does diffraction increase with magnification? Because you're magnifying the effects of it. Easier to see the softening as the mag goes up...
If noticeable diffraction is diffracted light spilling half way into adjacent pixels then what effect would movement, as little a a 1/4 the width of a pixel, have on diffraction?...
Images have to be sharpened due to the way that the sensor records the data. No matter how much you think you're defeating diffraction at some point, either in camera or in post, you have to sharpen your photos. Sharpening an image does not decrease diffraction...
I'd argue that a lot of what you are blaming on diffraction is actually motion amplified diffraction, an effect I like to call macro motion blur. It's not as obvious as traditional motion blur in an image, but it will increase diffraction softening. You're getting sharper images at lower Fstops because your flash duration gets shorter...
Although not as obvious as freezing a bullet as it's passing through an apple flash based macro is a form of flash based stop motion photography. The shorter your flash duration the sharper your images will be.
Last, but certainly not least, I'd like you to point out a single one of my images that's "crunchy" because it's over sharpened.
Focal length divided by the aperture diameter = Fstop. Does the focal length of a lens change as the magnification increases? Yes, if your using a lens that has internal focusing the focal length will decrease with the lens set to minimum focus. But it's not a huge drop, less than 50% for a macro lens, and even less for non macro lenses. Canon's 100mm macro is about a 72mm lens at 1x, and the EF-S 60mm is 37mm. I use the later for shooting macro cause it only takes 37mm of extension to get that lens to 2x.
I understand effective aperture as it relates to exposure. When you approach, and pass, life size magnification the amount of surface area that's reflecting light back into the lens drops dramatically. So you need more light to expose the scene. Got it, no problem. But I don't think that effective aperture really applies when you're trying to figure out diffraction effects. The physical aperture that the light is passing though is not changing, and that's what's causing the light to bend (cone). So me thinks that two things are happening: As the mag increases the effects of diffraction are being magnified so that they are easier to see. The other is that it's taking a lot more light to expose the scene (effective aperture comes into play here), so motion is going to cause diffraction to get worse. There could be more to it than that, and I could be totally out to lunch. But there would have to be something in the lens physically changing to cause diffraction to increase. Could also be something as simple as the magnification itself that's forcing the light to cone out more. Effective Fstop seems to me to be no more than a convenient way to calculate diffraction effects. But I just don't think that the effective Fstop itself is what's causing diffraction to increase -I think there's a lot more to it.
P.S. I get sharp images at high mag and Fstop cause I understand that diffraction isn't the monster that the macro community at large has made it out to be. Most of you are fooling yourselves. There's noticeable diffraction in the green channel at F4 and 1x no matter what sensor you use...
bclaff
Forum Pro
The effective aperture does matter and you're close when you say it's the "magnification".
It's not the physical aperture that matters but the exit pupil; and the exit pupil moves away from the image plane as you focus closer which is why effective aperture goes up.
So, it's not the magnification but the location of the exit pupil.
The further away it is the more the "cone" spreads out.
Isn't the big advantage of a close-up lens over tubes (or bellows) the avoidance of the loss of light ? With tubes, the further the lens is from the sensor, the dimmer the image.
This doesn't matter for still subjects in the studio, but it does for live insects etc.
The other point to consider is that some lenses have floating elements, which are not going to work correctly with tubes.
The stated focal length of a lens applies only at infinity. As you move the lens further away from the sensor, the effective focal length increases. Therefore the f number increases.
This applies to traditional prime lenses that move to focus. Many modern designs focus by shifting an internal group of elements, like a zoom lens.
I'd also argue that what most macro shooters call diffraction is actually motion amplified diffraction, or what I like to call macro motion blur. I've lost count of the number of times I've been asked "how many frames did you take for that stack" even though every one of my photos is a single frame. Taking as much control of the motion as possible, and freezing what's left with a properly diffused flash, is what makes my images seem stacked. Well, that and knowing where to put the area of acceptable focus
gardenersassistant
Veteran Member
With the same framing and the same depth of field (i.e. the same effective aperture) don't you end up with the same illumination requirement? (Genuine question. My hunch is that you do, but that is all it is, a hunch.)
My thinking is along these lines. Let's suppose I'm photographing a scene which requires 1:1 magnification. When I use f/22 with a close-up lens the effective aperture remains at f/22 irrespective of the magnification. If, on the same camera, I use a macro lens instead, I have to dial the aperture back to f/11 to get the same depth of field; at 1:1 this is an effective aperture of f/22. I will need the same flash power in either case (or get the same shutter speed for the same ISO if using available light).
John K
Forum Pro
OK, and that makes sense.
bclaff
Forum Pro
This is a very very common misconception.
Light is lost in both cases but the amount is different as well as the implications for working distance.
See the PhotonsToPhotos Optics Primer - Effective Aperture for a good explicit example.
Michael Benveniste
Veteran Member
You're correct when it comes to taking the shot, but with a close-up lens you can have more light to compose and focus with. However sometimes, that shorter working distance can make make the "same illumination requirement" harder to achieve.
[/QUOTE]
My set of Kenko tubes work just fine with my 105mm VR, but the change in focal length can make predicting the exact maximum magnification and working distance a bit harder. Bill Claff's calculators do take the change into account, though.
Keyboard shortcuts
- f
- Forum