Macro Choice of F-stop

[ellery]

<p>Ok, so ive been doing macro for 1 week now...got my macro lens on 3/26/12 - tamron 90mm f2.8....<br /><br />Anyway, a PN member was kind enough to give me this advice both on a couple of my shots, but somehow I find this advice contrary to what the books and common prevailing internet wisdom would state and wanted to open the subject for discussion (as I have studied photography, I found many topics not totally clear, with grey areas so it makes since)<br /><br />Basically, the advice I was given was to operate my macro (and any lens for that matter) at f2.8 to f5.6 for best results as far as sharpness...that much I can generally agree with, although I think that some have sweet spots even at smaller apertures around f8 if I recall....anyway...<br /><br />But in macro, it is as I understand in obsessively reading on the net and in my first week of attemps, it is a balance between sharpness/defraction and DOF...and in the end for "true macro" that is 1:1 - f-stops are mostly f11 minimal, more so I find myself at f14-f16...and higher if I need to, up to f22.<br /><br />Now I am aware that at f14, my sharpness falls as compared to say f8 or f5.6...but when I try and go to even f8 when at 1:1, the DOF is so small....not to mention at f5.6. And this may be why the websites (many of them, including PN) state to pretty much live at f14 ish for 1:1 macro....but by this PN member I am told that is a "common mistake"....<br /><br />Also I was advised to not necessarily use 1:1, and that I can crop quite a bit acceptably...this would afford me more DOF - this is true and I have backed off a bit to expand my DOF, but for many of the tiny bugs so far that I have encountered (see my macro folder), backing off seem problematic...even at 1:1, I am at times cropping significantly.....once I start seeing bigger spiders and grasshoppers (right now they are like infants) I can do this though I guess if needed<br /><br />Am I missing something?...I am skeptical of this advice, but being a beginner, I keep an open mind and realize the limitations of my education/experience.....at the same time, this "mistake" is sooooooo common in books printed (bryan peterson for example), I cannot help but wonder if this member may be mistaken?<br /><br />If my uderstanding at this point is mistaken, then someone needs to write to alot of websites and ammend content.<br /><br />Regards,<br />Ellery</p>

[bebu_lamar]

<p>You should do whatever works best for you and ignore all advice including mine. I agree with you and not your PN that most lenses are sharpest around f/8 and not between f/2.8-f/5.6. But we would have to test each lens to prove it either way. Now let's assume that your PN is correct on that, in my opinion f/2.8-5.6 provides too shallow DOF for macro work. May be your PN is into paper thin DOF and loves the very shallow DOF. Cropping to gain DOF is like using a smaller format camera to gain DOF. Now larger format cameras tend to cost more, i.e FX is more expensive than DX, and cropping is waisting your sensor that you paid dearly for. </p>

[dave_s]

<p>Ellery, hi again. I don't know whose advice it was to use a large aperture, but as all advice on photo.net, that's one person's opinion. At 1:1 and a set aperture of f/2.8 to 5.6 on a macro lens, you'll have little depth of field, but for some subjects this will be OK.</p>

<p>You have hit on a key point in close-up/macro: it's a fight between depth of field and aberrations (which improve at small apertures) and diffraction (which degrades the image at small apertures). One way around this is <a href="http://en.wikipedia.org/wiki/Focus_stacking">focus stacking</a>, if your camera and subject are both motionless. This is easy to do in the digital age, but photographers have been doing it for decades with film photography.</p>

<p>Cropping an image won't help you-- unless I'm missing something. If you take a photo at, say, 1:3, and then crop out the center third (by linear dimension), you'll just magnify the blur. (A fancy way of saying this would be that you need a 3x smaller circle of confusion to get the same depth of field if you are enlarging 3x.)</p>

<p>The other thing you might try is to ignore diffraction, and shoot at your smallest aperture. See if you get the results you want. There is a fellow named <a href="http://www.google.ca/search?q=books+by+alfred+blaker&hl=en&rls=com.microsoft:en-ca&prmd=ivnso&ei=oaZ4T4iYBOiWiALI6synDg&start=0&sa=N">Alfred Blaker</a>, a university technical photographer, who advised that approach, at least to some extent, in his books from the 1970s. Some of his published 35mm shots were at an effective f/64. He broke all the rules and got excellent results. In the end, it's the photo that counts, not how you got there.</p>

<p>Last time I shot macro was probably on Kodachrome 25 . . . . so my advice will be dated. Look for photo.net posts by a guy named Dan Fromm-- scientific photographer who knows a lot about the optics of photomacrography.</p>

[SCL]

<p>One thing to add to the list of many to think about in macro work, is that when you stop a lens down too much, you may experience loss of sharpness due to diffraction, sort of defeating the purpose of increasing DOF for sharpness. An easy solution, especially as you are so new to macro work, and eager to experiment, is stacking of images to increase DOF. If you are doing your post processing in Photoshop, you already have the software to do this at no extra cost. Essentially you shoot a series of macro shots of the same subject, same exposure, etc., but at different points of focus....stack the images together and let the software combine the layers and keep the sharpest points of each layer...blending them all together to produce a macro subject with incredible DOF. Rather than go into a long explanation of how to do it here, taking up space and readers' attention...if you would like to hear more, and how to do it on a shoestring, drop me a line.</p>

[starvy]

I am using a makeshift macro setup with an extension tube. I use a 135mm 2.8 lens. It closes down to f/16 and after spending countless hours I have worked out that anything below f/8 is almost impossible to pull off for my style of photography. So I tend to shoot mostly at f/11.

 

As others have said, this is trial and error. See what you like and take it from there. Much also depends on the where the light is coming from as well as what kind of object you might be shooting.

[paddler4]

<blockquote>

<p>Basically, the advice I was given was to operate my macro (and any lens for that matter) at f2.8 to f5.6 for best results as far as sharpness...that much I can generally agree with, although I think that some have sweet spots even at smaller apertures around f8 if I recall.</p>

</blockquote>

<p>Bad advice, IMHO.</p>

<p>Leaving aside DOF, virtually no lens is at its optimal sharpness wide open. Depending on what you are shooting, the sweet spot is probably somewhere within a stop of f/8. My guess (you can test this out for yourself) is that you can close down a few stops from there without noticing any degradation, unless you print large.</p>

<p>However, this is really a moot point with macro, where shallow DOF dominates the impression an image creates. Unless you are shooting something absolutely flat, you won't get enough DOF at f/2.8 (or anything close) to be useful at macro distances.</p>

<p>If you are shooting something static, so you can maintain the alignment of the camera, you can shoot at the sweet spot and stack images in software for more DOF. (Not all images stack well, but that is another issue). If you don't stack, you are likely to find that opening the lens to more than f/11 will give you unacceptable results at macro distances.</p>

<p>What you should be concerned about is the impression of sharpness in your image, not the optical sharpness of the lens in isolation. Depending on the image, if find that that extra DOF more than offsets a minor loss of sharpness from diffraction. You will have to experiment to see what works for you, but I find that f/13 is usually fine (even with a 50D, which experiences diffraction at a lower stop than some because of the pixel density). For flowers that don't have a lot of detail, I've been able to go to f/20 on occasion, printing at 8 x 10. Beyond f/20, things start deteriorating more.</p>

<p>I would not back off. that reduces the amount of information you have for the part of the image you want.</p>

<p>I'll post a few examples, although it is hard to check out detail at the low resolution you get on the web. However, I really urge you to try this yourself, to see what works with the kinds of images you want. Pick something that will stay put (not bugs), and shot at different apertures. Keep track of what is what, and then examine them to see which you like best.</p>

<p>f/13, 50D, 100mm macro, 36mm extension:<br>

<img src="http://dkoretz.smugmug.com/Bugs/butterflies-damselflies/i-DscQRD3/0/L/MG7252-L.jpg" alt="" /></p>

<p>same setup:<br>

<img src="http://dkoretz.smugmug.com/Bugs/butterflies-damselflies/i-k3s69PC/1/L/MG7328-L.jpg" alt="" width="800" height="559" /></p>

<p>XTi, 60mm macro, no extension, f/20</p>

<p><img src="http://dkoretz.smugmug.com/Flowers/Flowers-and-mushrooms/IMG2212810/498633502_RJ8cq-L.jpg" alt="" /></p>

[ellery]

<p>thanks all....<br /><br />I am aware of focus stacking...I tried it with a paper clip 1:1 shot friday night and used a free program (if I recall it is called combineZM) and was pretty amazed at the result...Indeed today I shot a few shots of some flowers and within doing so shot some 3 shot series of variable focus and will try it out and see how it does...I can imagine some subjects would be difficult or impossible to stack...obviously if they are a bug or animal or whatever that are moving, it would be difficult...<br /><br />I have tried shooting at f5.6 (which with my lens, you cannot shoot 1:1 I believe at less than 5.6 in reality) - the DOF is paper thin....ill post this attempt in a bit for folks to see...it really shows how thin the DOF is at f5.6 @ 1:1....f8 is a bit better, but still, it is quite thin...so far for my purposes in chasing insects in the backyard in the limited time I have f11-f14 (depending on what I am shooting, how parrallel I am, etc)...but I will frequently hit f16-f22 if I want much more of the insect in focus...even at f22 at 1:1 the DOF is not massive by any stretch....<br /><br />Im sure that folks have shot PARTICULAR macro shots at f5.6, but if a person is to give a newb advice on macro shooting, many times you are trying to give roughly generally the most applicable advice....and it seems very apparent that f14-f16 ish (stress "ish") is a good place for folks to start, then experiment with more or less DOF and closely examine the results YOU get...so far I am please with "most" results up to f22. I have a shot of a bug at f5.6, and it really shows how thin we are talking here - ill post this shot in a few minutes...I can see me experimenting with f5.6 for 1:1 macro, but it will certainly not be a mainstay for this it would seem.<br /><br />For these reasons discussed, I think it explains why this advice is not advised to give to a newb...it is why I think books and websites all agree to live in the f11-f18 range, if not f22 at times if needed....and for that matter, I think it is why professionals choose to shoot at these ranges as well.....</p>

[jcuknz]

<p>Another wrinkle to the situation .... when you are working at 1:1 that f/8 aperture is actually f/16 while the f/11 is f/22 and f/16 is f/32 :-) <br>

My understanding of diffraction is that it depends on the physical size of the aperture so you find a longer lens has quite a large aperture and less diffraction.<br>

When I started photography I was confined to the studio for the first term and 'normally' worked at f/64 with an 8" lens and got sharp clean results ... diffraction only comes into the equation when you play with smaller cameras and their shorter focal length lenses.<br>

That f/64 marked on the lens could have been effectively f/128 for some of my closer shots with greater extension. No EXIF on plates so it is just my rose tinted memory of the time :-)</p>

[danny_low]

<p>A tack sharp badly composed macro photo is still a badly composed photo. So the most important thing in any macro photo is the same as in any photo, get the composition you want first. If that requires you shoot at f4 then shoot at f4. If it requires you shoot at f22 then shoot at f22. In the final analysis, the only reason for a macro is to get the composition that a regular lens will not get you.</p>

<p>It's nice to be able to use the optimal f-stop but sometimes that will not get you the DOF you need for the composition. Sometimes it will give you too much DOF and background clutter becomes a distraction as it is too sharp and noticeable.</p>

<p>So get the composition first and try to get the f-stop that gives you the sharpest photo and still maintain the composition.</p>

<p>Danny Low</p>

 

[Mattman944]

<p>How much diffraction is acceptable will depend on the sensor pixel density and how the image is displayed. With my setup (40D, 100mm non-IS macro), f11 is as good as f8, f16 is almost as good. f22 is usable in some situations, f32 is not usable in most situations. </p>

<p>Note that with sharpening applied and at 50%, equivalent to a web display or small print, diffraction is less noticeable.</p>

<p>The bad advice I often see, is people saying a 700 pixel web image shot at f16 isn't sharp because of diffraction. It may not be sharp at 100%, but if it isn't sharp at 700 pixels, it is because of another reason.</p>

<p>http://www.mattman944.com/photodotnet/diffraction%20test.html</p>

 

[ellery]

<p>Danny - well, my experience so far in doing macro is that the different of f22 and f8 as far as the "background clutter" is the same....the difference in DOF in this wide range of f-stops gives you relatively only a bit more DOF...on the scale of a fly or a moth, it may be the different between getting most of the bug in focus and only half of it, but will not really make much a difference as far as beyond this....my background at 1:1 at nearly any f-stop seems to be totally blurred...I may be wrong about that though....ill compare some images later...</p>

[ellery]

<p>@JC Unks ....yeah, i have read that...but with Nikon, what you see in the viewfinder is what you get...other cameras it is I understand as you put it....but I know what you mean I think.....or so I have read...</p>

[ellery]

<p>this is for another thread, but I have tried my best in whatever I shoot to keep in mind larger prints later...I love putting stuff on my FB and photo.net, but I try and keep in mind a desire to print a one in a lifetime shot in a larger version....having said that, I try and fill my frames with the composition I ultimately want (this is something I have STRUGGLED with, but inch forward a bit more every day).....<br /><br />Point taken about composition....I imagine with macro newbs the struggle to get the hang of just getting bugs in the focal plane and pressing the shutter is enough to distract composition...some of that is unavoidable I imagine....once my muscle memory improves, my brain can focus on more :D </p>

[jaydesi]

<p>Bugs are more lethargic in the morning while it's still very cool outside. Something to keep in mind if you'd like to try focus stacking. Dead bugs are also good candidates, but if you squish them, they tend to look a bit mangled (see attached). :)</p><div></div>

[ellery]

<p>ok, follow up question, and hopefully the PN member will come onto the thread as I have requested him too...but I was also advised that macro lenses at 1:1 are often at reduced quality:<br /><br />"First, a "macro " designed lens does not imply that it has to be used at such a close range that the DOF is measured in millimeters or less. That is incorrect. In fact, many commercial macro lens DO NOT provide excellent results at close range no matter what f-stop is employed. There are limited by their design and build quality."<br /><br /><br />Also I was advised that as such, I can just back off from 1:1 and come back up and open up aperture....<br /><br />Hopefully he will come on here and likely better explain the advice, but still, I am skeptical....I like the 1:1, and frankly, I already am itching for some extension tubes for later once I get things down better....some of the shots I would like just a bit more detail - the idea for many of the smaller bugs I shot so far and backing off from 1:1 I find undesirable...</p>

[SCL]

<p>One thing which hasn't been mentioned in this thread yet is the use of flash to provide additional illumination, and/or directional light on the macro subject. Although I have a macro ring light, I rarely use it as most of my shots are taken in relatively strong light. I have several friends, however, who want to catch certain insects, but they are too active at warmer temperatures, so they go out around dawn and use a flash to provide the necessary light. Years ago, a lab I worked at used a spray of cooled carbon dioxide to slow down the insects...it would keep them still for a minute or so while they were being photographed, or sometimes positioned for a macro shot. They also used multiple flashes for lighting.</p>

[ellery]

<p>yep, I use an external flash alot so far...fired off camera..</p>

[paddler4]

<blockquote>

<p>"First, a "macro " designed lens does not imply that it has to be used at such a close range that the DOF is measured in millimeters or less. That is incorrect. In fact, many commercial macro lens DO NOT provide excellent results at close range no matter what f-stop is employed. There are limited by their design and build quality."</p>

</blockquote>

<p>The first part is right, the second part isn't.</p>

<p>Most macro lenses can be used at any distance. For example, I use my 100mm as a telephoto lens, and the 60 makes a nice portrait lens. That is one (of several) advantages of a macro lens over, say, extension tubes, which eliminate distant focusing.</p>

<p>Re this claim: "many commercial macro lens DO NOT provide excellent results at close range": I don't know what macro lenses the poster is referring to, but this is not true of the three I have used (the EF 50 f/2.5, the EF-S 60 f/2.8, and the EF 100 L f/2.8). All produce superb images at minimum focusing distance. I typically back off from minimum focusing distance a tiny bit just to give myself wiggle room for focusing, but there is no reason to back off for reasons of optical quality.</p>

<p>Frankly, given what you have relayed to us from that original advice, I would put that aside aside rather than trying to reconcile it with advice from elsewhere. There are a number of dedicated macro forums (e.g., http://www.dgrin.com/forumdisplay.php?f=23) where you can find both tutorials and excellent advice.</p>

[ellery]

<p><a href="http://www.dgrin.com/showthread.php?t=58028">http://www.dgrin.com/showthread.php?t=58028</a><br /><br />Thanks Matthew...I saw this series from "LordV" (who seems to be quite a good macro photog) - this confirmed what my experience with even f5.6 at 1:1 was been... *nearly* far too narrow DOF for most desired shots...f8 if you are careful seems to be acceptable if parrallel *mostly*...and even at f8 it aint like you have massive DOF by any stretch...<br /><br />THis has all made me ask a strange question:<br /><br />What is the shape of the DOF? I mean the area in a 3D manner...it is likely not a flat plane right? the focal "plane", I wonder how curved is it (if it is curved)? That may be why experiementing with not only perfectly parallel, but as lordV put in his post above, but on a 45 degree angle with the angle tilted upward a bit....not sure if these thoughts are making since?</p>

[JDMvW]

<p>I have the Tamron 90mm Macro too. It is a bargain and high-quality too. </p>

<p>One of the key problems in any macro work is the shallow depth of field. Opening up isn't going to help unless you want to isolate larger things from the background (as in flowers, etc.). On the other hand, diffraction does kick in as some point, so <strong>optimum</strong> aperture is always a compromise, or even a "contradiction". For real, 1:1, macro, you may even want to "<a href="http://en.wikipedia.org/wiki/Focus_stacking">stack focus</a>"<br>

Most macro lenses are designed to have a flatter curvature of focus than are 'normal' lenses.<br>

(details on the Tamron can be found in an older test on <a href="http://www.photozone.de/canon-eos/282-tamron-af-90mm-f28-di-sp-macro-test-report--review">Photozone.de</a>).</p>

[sravan]

<p>When folks talk about sharpest from the wide aperture side, they talk about f2.8 for the f1.x primes, f4 for the f2.8 primes and zooms and f5.6 for the f4 zooms. This means that the aberrations are minimized by this f stop. This does not mean the lens starts to deteriorate at this point. It is actually very hard to tell the difference between the sharpness for F5.6 and f11 for most lens.</p>

<p>Most lens are sharp till diffraction limits are reached. Now it is important to note that the F stop for diffraction limit effects is dependent on the sensor size and density and not the lens. You need to check it online, but for a full frame sensor in the 20MP range, the diffraction effects start for around F11 (Canon 5D3 for example). For a Full frame sensor in the 12MP range, the F stop for diffraction is F13 (Canon 5D classic for example). Now beyond that diffraction can start to cause issues, but it is not immediately noticeable. The absolute F stop when diffraction becomes a clear issue is again based on the sensor size. For the 20MP full frame sensor it is normally in the range of F22. for the 12MP Full frame sensor it is around F26. </p>

<p>So taking the example of the Canon 5D3, and the 100 F2.8macro lens, you will have minimal distortions from F5.6 to F11. Obviously F11 has the maximum DOF.<br>

After F11 while the diffraction starts to affect image quality, for most purposes you will get great resolution until F14. after that you will start to see the resolution go down.<br>

I do not go below F16 on my 5D classic. I don't do much macro now but now I wouldn't go below F14 for my 5D3.</p>

<p>Now the other issues you have with macro lens is the field of curvature. The plane of focus is not flat like you would expect at the shortest focus distances. It is actually curved a bit. The better lens have more flatter plane of focus. Most true 1:1 macro lens are designed to keep the focal plane as flat as possible and that is why they perform better for flat subjects than getting 1:1 using other methods like extensions, bellows or reverse lens designs. Not to say the other ways are bad. So if you have a curvy subject, having a curvy field of focus might help if the curvature is the same type.</p>

<p>The field of focus is not tilted by default for most well designed lens. It is curved. That brings to the use of Tilt Shift lens for macro. One other way to get good DOF without going too deep in the F number is to tilt the field of focus. This is done using the tilt shift lens or bellows if you are using them. With a tilt shift lens you need to use extensions again to get near 1:1 macro. With proper bellows you get both 1:1 as well as the ability to tilt in one and that is why many prefer it to a straight 1:1 macro lens. The only problem is the subject matter where you can use this to shoot macro comes down. I personally find it hard to do tilt, focus (Tilt shift lens are all manual focus) and shoot for insects. I love doing small jewellery items using Tilt shift since they don't move and i can take my time. And mostly i don't need 1:1 macro also as the items are not that small.</p>

[ellery]

<p>Thanks sravan...you echoed what I have essentially read...I have a D90..I think it is 12.3 mp and a tamron 90mm f2.8 macro lens.<br /><br />I sort of suspected that the DOF would have a bit of curve to it...makes since...interesting points on the tilt shift lens..seems like I recall them using those for architecture as well...which seems for obvious reasons I think.<br /><br />Also, I was just glancing through the photo critique forum and looking at photos, saw a pretty nice flower macro shot...f29 shot...pretty good detail...<br /><a href="../photo/15459792">http://www.photo.net/photo/15459792</a><br /><br />I have I think noticed on my D90 setup defraction effects above f16 only in certain insects I have shot so far...It seems that for me so far, I percieve what I think is defraction at around f18 and above...sometimes it is not noticable, but for like finer lines and things, I think it becomes more noticable...expecially if the subject is VERY small...as in this shot, when I went above as I recall f16, I saw what I think was more defraction along that little sucker thingie..<br /><br /><a href="../photo/15453032&size=lg">http://www.photo.net/photo/15453032&size=lg</a><br /><br />Anyway...f11-f14 seems to for me be very sharp so far, I have been staying in that range for what I have been doing now...i will be experimenting with f8 more, but I seem to struggle to get what I want in the focal plan at f5.6-f8 with moving insects!!...probably just need more practice for using that narrow of DOF...<br /><br /><br />Well, Ill keep at it...thanks for the advice folks...keep it coming if you feel compelled...I am about to post a differnt topic in the realm of macro...</p>

[ellery]

<p>""On the other hand, diffraction does kick in as some point, so <strong>optimum</strong> aperture is always a compromise, or even a "contradiction". "<br /><br />JDM von Weinberg...yes, that seems apparent to me at this point...what the photo.net member had suggested instead of shooting at 1:1 with reduced DOF was to back off 1:1, then crop more after the fact to improve DOF and sacrifice perhaps resolution a bit...but as I communicated with him...in many situations, backing off 1:1 simly means bringing some things out of resolution at all, thus making a sharper result irrelevant...or so it seems to me...<br /><br />It seems like when we are arguing about this he wants to have his cake and eat it too :D</p>