The Three Main Optical Issues
The three main optical issues that we have to deal with okay, depth of field is truly uh well they're all they're all very important but if the field is something that is just almost impossible to work with him frankly before the digital age was impossible to work with uh as as well as we will see as your magnification increases your depth of field shrinks very very, very dramatically that's probably the biggest understatement I'm going toe make here today now you can use smaller apertures we're all we're all familiar with depth of field when we do a landscape way we close down to get the flowers in the mountains will short so you could use smaller apertures but when we get into these magnification as we we come up against an optical phenomenon known as diffraction where the image just becomes soft it has to do with the way of nature of light there's really nothing we can do to avoid it uh as with any use of depth of field careful subject orientation maybe we'll make the best use of wh...
atever available depth of field you have and then we get into really what the solution is for not every image for a lot of images is the image the focus stacking where you take a series of pictures and you take the sharpest portion of each picture and you combine them in the computer so let's just take a look at at depth of field and how it is seen and how is problematic this is a photograph of a midge and this is my end my finished image my final image uh and this is where the stack of eighty six separate images combined if we look at this on the left is one image from that stack so that's what what my actual depth of field is if I would take a single picture that's what it would look like and they want on the right again is the combined image where I've combined my depth of field so let's go back that's the thing that's the finished picture uh here we have on the left we have ah one indigenous stack and on the right we have the finished image these are moth eggs he's a very, very small this is photographed the ten x now if in the in the film days I would have tried to shoot at an angle straight down from the top because I have to make maximum use of my depth of field. But now that I could stack I can choose an oblique angle like this and you could see that on the left is one image from that stack of images that I used to make this composite this picture on the right is the finished image and it took me two hundred and ninety one focus steps to get that that final image okay, and here again, this is a mosquito head, alright, and I I, uh, twenty x twenty times life size one image on the left you can see. In fact, if you look, I don't know how easy it is to see there, but you can see how eyes bulbous and what we're already. I picked one image where you can see this is already I start with the focus on the furthest point, and I worked my way in, and I've only got a small band focus there. So again, at twenty x in the film days, this is about what I would have gotten on the left. This is what I can get now using these extended depth of field techniques, and, you know, I I'm into the natural stuff, the bugs and the butterflies and things, but I also do some work for from a manufacturer that makes these incredibly, incredibly small canticle devices, and, uh, this is one that is already this is already stacked image, but he wanted to close up and he wanted at an oblique angle, so he wanted basically, he wanted this image and this this is now getting thie extreme of what I'm able to do with this with this technique, but he could see what one image look like on the left okay? And it took me. What does it say? That three hundred thirty two images to composite to get that depth of field and I'll be real frank with you. It also took me a lot of photo shop time because when you've got a very complex image like that and you put it together as good as the software is to do this, you got a lot of artifacts. You got a lot of stuff, you got to clean up, so you do need, uh, really good for not all images, but for a lot of them, you do need some pretty good photo shop skills in particular, something you don't maybe use all that much is not not just the universal control, the contrast in the color balance, but the actual pixel editing. You've got to be pretty good at pixel editing for a lot of these things, uh, kind of joking with, uh, when individuals here the other day I am I've been here in a sense, oh, west coast here since seventy nine. But I grew up in new york, so I tend when I think I got a lot of material and I want to cover I tend to talk fast, okay, so I I apologize for that, but this little chart again you don't need to know these numbers I just want to really reinforce the point that I just gave you at the top you have a magnification and then you have your depth of field and I encourage you to start thinking in the metric system okay and you'll see why here not only milk that's the finished picture was twenty five point four millimeters in an inch but we're talking now microns which are thousands of a millimeter we're talking at a scale that is beyond what most people I deal with on a regular basis unless you brad intel or into some sort of scientific endeavour but I'm just going to make show two points on this on this chart and he could see and when I say that your problems increase exponentially they dio at one access so this is what my macro lens at one to one I can get a good nice clear depth of field for about one millimeter and that doesn't sound like much you say my god how can I know what you can you know if you use it properly and that one millimeter is a thousand microns okay let's not just go through the trouble let's look at te next kind of in the middle because that's a very very nice area they're working at ten millimeters might depth of field has dropped from ah thousand microbes toe eight microns okay from one millimeter to eight thousands of a millimeter. So now you can see why take so many pictures if you're trying to accumulate to get a shot that has a sense of depth of field, and again, if if you're not a metric system person, and even if you are most people don't think in terms of microns millimeters, so down below, I give you a few sort of benchmarks, if you would standard cd is about one point two millimetres thick that's twelve hundred microns you know. And again you can look at these and this is this is maybe just tow reinforce the point that I wanted to make you mind the head of a pin is about a millimeter. About a thousand microns uh, typical grain assault. Obviously they're all different sizes, but about three hundred microns red blood cell is about six to nine microns and a sheet of paper. The copy paper that you have in your printer at home. That's actually somewhere between ninety seven and one hundred eleven microns. So you could see that your depth of field in some cases here is way, way less than even the thickness of a sheet of paper. And you could see if you look at the right hand column inches you khun see definitely why we don't use it, yeah. I have to sit and look at those numbers to try and think how I would even say them you know what? These scientific notation you don't work in inches in this field ok, the next um optical issue that we have to deal with this diffraction um and the fraction is caused by the wave nature of light it bends as it goes through a through an opening and it's unavoidable when we're dealing with the full light spectrum, you know, if there's a limit to what we can do with visible light after that you start going into electron microscopes you get you start getting into all more exotic things that were not obviously going touch upon here, but you avoid the problems of the wave nature of light. Um the problem is we have this tiny, tiny deaf the fields are as photographers are natural inclination is I'm just going to stop this lens down, I'm going to use a small aperture and I'll get lots of depth of field you can't do it anymore at thes magnification because you hit diffraction and give you an example here in a little while, but diffraction just destroys an image quality just turns your images to mush, so you have to avoid it uh, very consistent and that's why it's important to know what magnification you working at? Because it'll kick in at different points of different magnification you know and as photographers we work in f stops we think of aperture f stops f numbers that two point eight four five six eleven, sixteen twenty two okay and that's fine. The problem is these numbers are only valid these numbers are only accurate for subject aside affinity ok, so if I take a fifty millimeter to eight lens and I take it outside into a landscaping and I'll not infinity but you know a fairly normal distance ten feet to affinity to eight it's accurately to eight if I put it on a bellows if I put it on extension tube's it's no longer too eh it's going to be small it's going to be you know it's going to be f five six it's going to be f eleven it's going? It depends how much you magnified the more you magnify it small this effective apertures and this is the area when I was putting us together I think you know don't really want to get into the weeds here with this stuff and I do I really have to because you have to understand and you'll see very clearly the impact this could have on your pictures this's ah a little bit everything every field of photography has its own technique it has its technology and it has things need to know this is grant I'll grant you right now this is a little more a little more tech it is a little more of a foundation that you need to understand toe work effectively um you know but my offer toil photography I've ever done in most things in life uh you try to get the tools and the techniques to be second nature because otherwise you can't be creative you can't be creative if if I'm sitting there thinking oh my gosh, you know what's this what's this house my tripod work musician can't be creative and created music if he has to think ok let's see b flat you know, what key is that the equipment, the technique that has to become second nature and you have to have a foundation and this is part of the foundation you won't think about this a whole lot in the terms were talking about it here now necessarily, but it will be there and it'll just be oh yeah it's just like if you do ah portrait and you've got a nice cannon eighty five one two lens and you want to really soft background and just you know, you don't even think you don't think okay, let's see what I've stopped though I need one point to you know, our f sixteen I can't remember now you don't think that you just open the lens upto one point two you shoot it eventually become sort of the same thing here and formulas you don't really need to know, but I want to show you that affect how the effect of aperture is really directly related to your magnification. In fact, f in this formula is the mark, the mark aperture. Like a two eight for and to get the effect of apple tree literally multiply it times magnification, magnification plus one. Okay, now, why? Why? Why did I even bring this up? I didn't. You know, this isn't a physics classes isn't a math class now. It's za photography session. But on the left we have at five x a stacked image that was shot at five x with the lens set at three point five. Okay, my effective aperture is f twenty one on that left hand shot. This is the this is this cannon lands. You know we have here on the right. We have ah, a single image. I said, you know, you know, I can't be bothered with the stacking stuff. This lens goes down to f sixteen. No problem. He's going to shoot this baby it f sixteen. Okay, so now, at this size, this man, a patient and it's hard for me to tell on the screen how much you know you can really see the difference so what I did was I just took a section the same section in both at one the one on the screen and this is what they look like you no wonder one so you can see the difference I think hopefully very obviously here everybody give a couple of head nods can you see the difference, eh yeah the the image on the right is totally destroyed because of diffraction and this is not something you typically will encounter in ordinary photography because they're your f stops are fairly accurate and lo and behold the camera manufacturers know never to ah you know, make a lens for you for thirty five millimetre or on a psc center that you could stop down to f ninety six because you're going to think it's the world's worst lens in fact when can it came out with this lens? They made it very easy toe work at five acts and there are there were more than one person I've seen that got that wins is the oddest lenses garbage you know these pictures what a piece of junk you know, I really wasted my money now it's a great lands but they're out there at five x and they're taking the pictures I'd have sixteen because they think they need to stop that protect the fields so they're getting stuff like you see on the right there when in reality, lynch is more than capable enough, if you use it properly and, uh, I have benchmarks now that this is this is tricky way we used to have everybody had thirty five millimeter pretty much now we have different slice sensors, but the three most common or the micro four thirds the a p s c I call it ap sea and thirty five millimeter format, which is twenty four by thirty six millimeter center. Now, just you know, we're not going to get into the physics and wise and wherefores, but these are the benchmarks I I used in other words, I'm photographing with the cans that have which are a pfc I try to avoid any combination that will get me down with an effective after small in f twenty two soon as soon as I look and I don't calculate this every time, but when I'm contemplating a setup for something I'm going to use on my desktop studio, if you would indoors, I think, well, what if I did this and I look and say, gosh, that is being effective after a forty five? I can't I can't work that I got to come up with another solution because I know with that size sensor once I get below with twenty two things, that things were going to get really soft really fast you got a little more leeway thirty five millimetre I use that to and if you're one of these real pixel peepers and you just got yourself you know sony with forty two megapixels or canon with fifty mics because you're going to see things that and they're going to say well you know this camera's diffraction limited at five six r f eight or something like that and yeah maybe but good luck when you get into the macro will you you're not going to get those types of apertures and if you did you have image tax that were six, seven hundred pictures long and you know you'd be running a stack for a day and a half you know why you went on vacation or something to get to get an image out of the thing so now these are the benchmarks I used not your benchmarks could be different if you're just doing small pictures on the internet you may be able to except a little more diffraction of the smaller it is the less is less noticeable it is if you're you know if you got to make the big twenty by thirty prints on the wall well then you you know you want to go the other way instead of twenty two I may be trying to get f sixteen or something like that as my smallest effect of effect of the keywords effective aperture now you're gonna find when you get it until the higher magnification is that you simply cannot always get it where you want theological solutions don't exist yeah, they may be do exist but I have a friend who works from telling he was telling me about one of the lenses that they usedto create their chips and it's like a million dollars you know there's only like one or two of them in the world, so yeah, I mean exist but you don't have I don't have intel has one um and the last optical issue is something we think about in conventional photography but not to the degree we need to think about it and we're working at higher magnification that's vibration now mirrors mirror single lens reflex I don't know what cameras you guys are using now you single lens reflex or be using from from million years and is a mirror that goes up flops up flops down and that creates vibrations and that's that's almost a no brainer. I don't even talk about that anymore because anybody that does close up work they know that the mirror creates vibrations so you you have a work around for that you have a mirror, a lockup or you you know you have other missions that you use so I don't even talk about yes, you know the mirrors that there is a really bad actor, you got it, you got it take care of that but what a lot of people don't think about is the shutter vibration most of our camera still have mechanical shutters now this is many magnitudes less vibration in the mirror flopping up and down so people will say well I got this new camera it's a merrill this camera I don't have to I have to worry about vibration now that's not true because he's still more than likely in the vast majority cases you'll still have a mechanical shudder even though it's controlled electronically there two blades that come and they move and when they hit the first one hits is a little bit of vibration set up you don't see it in ninety nine percent of conventional photographer photography I guarantee you that you'll see it when you start doing tabletop set up ten twenty fifty x and you will definitely see if you got a camera mounted on a microscope where it's hard couples right toe everything and you're working at even higher magnification sometimes so the hand of the shutter is something you have to you have to have to think about handling your camera you know we were taking as we'll see we're taking stages of focus where we're changing the focus we're doing things on the way we're handling the camera we're changing maybe the the ice or something you need to let things settle down a little bit after you don't you don't really until I have ten x magnified live you my eyes just popped open I said holy smokes you know I'd be downstairs working and the dryer on the outside of the house or the clothes wash it would be on spin cycle and I look at the ten x magnification and everything be shaking you know, uh, somebody walks heavily across the room upstairs, everything everything shakes. So you really, really have tio pay attention to handling and external environmental sources of vibration now that you typically the urine house you could control, you know? Yeah, yeah, sit down. You know, run around upstairs, you done with laundry, you know? And I can work external could be tough. Most of us don't have to deal with my external. I mean, you know, if you live in the city on a very busy street, I did a job for comcast. We're in a high rise and I had photographs and things and the elevators were right next next to where they had me set up and the building actually moved a little bit and I think this is fine for lots of things, but this is a little bit of a problem for me and, you know, just really interesting to two cases of stick out in my mind about environmental vibration, I had a fella, eh? Conversations with online and he was from finland and they lived next to a rock quarry so when they were working at the rock quarry between blowing things up unloading my truck so he couldn't work and add another fella recently who somewhere south american might have in costa rica with is an active volcano going all the time and he literally has pictures of the volcano from his deck I mean, it looks like mount rainier does from downtown salem and you see the smoke and he says, yeah, I can't work a lot of the time anymore what can I do? Eliminate the external vibrations fortunately, this is something we don't have to deal with very much and a little bit of external vibration that we have weaken were usually in control and so you know, external vibration yeah, you know you gotta pay attention to that the loud music good grief I've had if you had speakers on if you've got a real baseball line going on now you know everything's moved uh in the mirror yeah, you all know about that everybody knows about the shutter vibration okay? A fully mechanical shadow will negatively impact image quality guaranteed guaranteed I don't care if you've got your setup embedded in cement I've got a microscope please about a hundred pounds at home I still worry about it it's still the shutter vibration so if you have a fully mechanical shudder uh you can get away from you get around this by using a very long shutter speed that seems weird that seems counter intuitive but the reason is because the shutter vibration that causes problems typically occurs for just a a few milliseconds at the very beginning of the exposure. So yeah boom click the shutter opens and I think shake but they stop very quickly so if you gotta want second explorers or two second exposure ninety nine ninety five percenter exposure everything dead calm so ironically, you know you can use long exposures to teo take care of ah shutter vibration problem you can use electronic flash electronic flash obviously the power levels we use in doing some fairly low so you're effective show to speed is the flash duration which which can often be sometimes five thousands of a second ten thousands of second speed lights you know, the on camera flashes that we use have very, very, very short flash durations and, um that will take care of usually most camera vibrations and if you're really obsessive compulsive and you have sweet like you can use both along shutter speed and flash with the second curtain sink and then you know then you got it licked you have to work in very subdued light, but you know, like a one second exposure with second currents sink and electronic flash man, you've taken care of all your camera vibration problems right that I don't resort to that because I now have a camera I use only cameras that have what's called an elektronik first shut occurred this has become mohr and more common uh many of the candid cameras have it is actually the only one night condom aware of the deep d a ten I think it is the latest nikon some of sony's have it some of the muralist cameras have it now too but what this is it's sort of a hybrid system when you're alive, you you looking the shutters actually open that's why you could see it because the lights hitting the censor when you initiate exposure typically what happened? What used to happen was the shutter was closed and then reopen again on dh he got that bang bang of the shutter going now with electronic first showed a curtain they electronically clear the shutter the shutter doesn't have to close to initiate the explosion, but they still use a rear mechanical curtain to finish the explosion, but at that point I'm done I don't care what the cheddar hits when that pictures done a little bit of vibration kicks in does not affect my pictures the difference could be night and day especially I never used him out my cameras on my microscope at least not this type of camera uh because because of the vibration from the shutter soon as I got cameras with this elektronik first shuter curtain I now will not come on the microphone before I used to have a step big, heavy duty separate stand and I would have separation between the camera and microscope so any camera vibration couldn't be carried over into the microscope so charles you mentioned marylise cameras it seems like marylise cameras that would eliminate a lot of the eliminated the mirror they include air over including but I say that's that's a no brainer most people are aware of that yeah, what a lot of people don't realize is that if you have a marylise that does not have an elektronik for showed a curtain, you're actually worse off than a single lens reflex that has merrill lockup because what happens is you're looking t the image the shutters open and then if it doesn't have electronics and the shutter has actually closed and then reopens to start exporting so you get you get bambam so so instead of having nothing happened mechanically you actually have a mechanical shop closing, reopening and I don't know if you you know you may even if you're not into ah uh this type of photography for awhile there some of these cameras they were having issues issue with something they called shutter shake to the point where in in certain cannon lettuce cameras they actually made a setting that you could set so that when you hit the, uh thing, that there would be a delayed, almost imperceptible but enough delay the bother people for that to die out that first down to die out before it opened again and so it's ironic but a marylise camera? Yes, it doesn't have the mirror, but it could give you a double mechanical shudder hit as opposed to a a single one or better yet, none at all. Now we're starting to see a few cameras with interchangeable lenses that have ah fully elektronik shutter. Okay, that's great! I can't wait for the day they have that uh, right now they don't the first shuter curtain works very, very well, fully elektronik would be even better. Um the fact, the only one I know interchangeable that's now that has a really functional, fully electronic shutter is one of these new sony ones I forget which one it is of new forty two mega pixel one, and there might be another sony model but that's great, I mean that that that will be yes, and now the scientific cameras that they make from microscope yeah, they're they're all electronic shows they don't none of them have mechanical shows, but you know what? I'm trying to get this, I don't use one, uh but but I always have to consider the work around. You know, how can I? How can I deal with vibration? That that that I do have?