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  #1  
Old June 11th, 2011, 12:17 PM
durangokid durangokid is offline
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Default Lens question for the experts

What lens would be good on a Canon for model photography? Iím using my wifeís Canon XSi with the kit lens EF-S 18-55 with IS. Now it may be operator error but Iím not getting the sharp images I would like. Iím sure there are a myriad of reasons why Iím not getting great photos but this is what I have learned reading the internet:

Set cameraís setting to highest MP (but not RAW)
Turned the aperture to the highest setting (focal length?)
ISO set by the camera at 100
Using four 85w florescent bulbs at 5500k with a 91cri
Using Picasa for basic editing

The images below are examples using these settings. You can see that the images are not that sharp. Iím not sure if that is due to the lens or operator error or both. The latter is likely the correct answer! It does seem that the images are sharper when they are loaded on my computer but on a web page, they donít look as good. Could it have something to do with the resolution? Do I need to resize them?

Sorry fellas, I know Iím all over the place here but itís getting a little frustrating. Here I thought you just buy an expensive camera, push a button and you will have beautiful photosÖnot! I have a hornet that I just completed and I canít seem to get all the variations in the paint that I worked so hard on, to come out. Any help would be greatly appreciated.








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  #2  
Old June 11th, 2011, 12:30 PM
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PlasticWeapons PlasticWeapons is offline
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Your photos look great. I believe it's the photo hosting site, Photobucket, which tends to degrade the photo quality some what - no, a lot.
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Last edited by PlasticWeapons; September 21st, 2013 at 11:55 AM.
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  #3  
Old June 11th, 2011, 01:55 PM
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It will take a little to explain. I have had that lens so I learned a lot about it:

First yo have to know that every lens has its own sweet spot of sharpness which is usual 3 stops up from the lowest aperture number for particular lens. In your case (f3.5-5.6) it was f11-16 and you will get the best sharpness with apertures between f11-16. Lower values than F11 causes the image to degrade due to diffraction, and I found any higher value than F16 is very unusable with your lens. Than you have DLA (Diffraction Limited Aperture) for your body which is the f8.4. DLA is mathematical calculation that approximates the aperture where diffraction begins to visibly affect image sharpness at the pixel level. So in your body-lens combination the sweet spot for sharpness should be f11.

Second, your camera is cropped sensor camera, which mean that 55mm focal length on your camera is actually longer focal length, 'cause you have to multiply it with crop factor for your body, which is 1.6x (your sensor is 22.2 x 14.8mm). It mean that when you shoot the photo with 55mm it is actually 88mm. The lover the focal length is, the lover is field of depth. So you should consider the combination of focal length range 28-40mm and f11-16. Actually, 35mm should give you the best results, but don't go with smaller aperture size than f16 (22 and smaller give you the very bad results). From the values I have read from your photos exif - f25, f32 and f36 you can not expect any god results.

Third, the total field of depth is distributed in a way that it covers 1/3 ahead of the focus point to 2/3 beyond focus point. So if you imagine two parallel lines orthogonal on the lens pointing line, where closer line is touching the closest point of object that should be in depth field and further one is touching the farthest point of object and the distance between them is, for example 24cm, your focal point should be 8cm beyond imaginary first parallel line and 16cm in front of second. In that way you will have the whole object in focus if f number you have set allows you that.

So it is on you to experiment a little within this value range I gave you to get the best results.

For a kit lens, this is not bad at all, but it is far away from a quality lens.

Hope I have help you a bit with my limited knowledge of English. If you do not understand something, I will try to explain better.
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  #4  
Old June 12th, 2011, 12:46 PM
durangokid durangokid is offline
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Wow, my head is spinning. I understood some of what you were sayingÖI think. Thanks for taking the time to write all of that. So I need to set my aperture to a lower number right? I had it all the way up to get more area into focus but if I understand you correctly, that degrades the resolution. Iíll try f11 and see if that helps. The part Iím not sure about is the focal length. Are you saying I should be closer to the object or farther? Unfortunately, you have to explain it as if I in the 6th grade.

My wife has a Canon EF 100mm f/2.8 Macro USM Lens, would that be better? It just seems with that lens you have to be so far away from the object.

Ryan, is there any options out there other than Photobucket that doesnít degrade the resolution?
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Old June 12th, 2011, 02:55 PM
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strikeeagle801 strikeeagle801 is offline
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I've got that lens as well. I really like using it for pictures of my kids, but have not used it much on models yet. I found this Wikipedia article to be helpful when explaining F-stops and focal lengths. Here's the most relevent part for me:

Quote:
Picture sharpness also varies with f-number. The optimal f-stop varies with the lens characteristics. For modern standard lenses having 6 or 7 elements, the sharpest image is often obtained around f/5.6–f/8
The Canon website says that the lens in question has 11 elements in 9 groups instead of 6-7, but I'm guessing that this range will still work rather well. I know that when Randy was helping me with my lenses in the past, he described f/8 as his "sweet spot" (the "perfect balance" between sharpness and depth) for his 100-400mm lens. I'd give f/5.6 or f/8 a try (letting the camera choose shutter speed and ISO) and see if that helps you out any with getting the results you want, and "tweak" it from there if needs be, but staying as close to that range as you can.

Aaron
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Old June 12th, 2011, 03:18 PM
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Ok, I will try to clarify you a little bit... the lower the focal length is, the larger the depth of field is. With 24mm you will have the larger depth of field, than with 55mm for the same f (aperture) number. Focal length of your camera is from 18mm to 55mm. So you will have to find a compromise, but my recommendation is to play with focal length between 35 and 55mm and with f11-16.
If the following part is what confusing you
Quote:
Second, your camera is cropped sensor camera, which mean that 55mm focal length on your camera is actually longer focal length, 'cause you have to multiply it with crop factor for your body, which is 1.6x (your sensor is 22.2 x 14.8mm). It mean that when you shoot the photo with 55mm it is actually 88mm. The lover the focal length is, the lover is field of depth.
I will try to clarify you, because this have nothing with shooting distance.
Full frame sensor is the sensor which dimensions are the same as at the regular 35mm film dimensions - 36mmx24mm. All lenses focal length were given for full frame sensor and so called "normal" lens for that size of film is nothing else but the mathematical calculation and is equal to diagonal of the film or sensor. In case of full frame sensor it is 43.26mm. In case of your sensor, dimensions are 22.2x14.8 so diagonal is equal to 26.68. So we have situation that 43.26/26.68=1.62 and this mean that your sensor can register 1.62x smaller area that full frame sensor and this is why we call it "crop" sensor. So if you set your focal length on your lens to 35mm it will be 35mm if you have body with full frame sensor, but with your sensor it will be 35mm x 1.6=56mm.
So when you finish composing the frame as you want, you should pay attention on distance from your lens of the closest and the farthest point of the object you want to be in focus. Distance from the closest point to the farthest point is required depth of field and it have to be distributed 1/3 to 2/3 regarding the focus point.

I am sorry if I make you even more confused, but it will be much easier to explain on some examples and I suppose my English imposing me some limitations as well. So you will benefit from same basic book about photography much more than from my writings here!
But I'm not saying that I ain't gonna answer you on any following question, just I'm not sure will you understand me properly... and my English sentences!
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  #7  
Old June 12th, 2011, 03:32 PM
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PlasticWeapons PlasticWeapons is offline
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It won't matter how tack sharp you can get your photos with camera gear and technique if the photo hosting site you upload your photos to downgrades the original photo's resolution when wanting to share pics with fellow modelers.

Anyone recommend a good (free) site that doesn't fiddle with the photo resolution post upload? Photobucket sucks.
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  #8  
Old June 12th, 2011, 03:45 PM
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@strikeeagle801
In my first post I gave characteristics for his particular lens. In his case (Canon 18-55mm 1:3.5-5.6 IS) sharpness deteriorate significantly if he go under f11 or above f16 for lens set at 55mm. For 28mm to 35mm best sharpness is at f5.6 and then deteriorate slightly toward the f11 but still sharp and is acceptable at f16. At 24mm best sharpness is at f5.6 deteriorate toward f8 and still acceptable at f11. For 18mm sharpest is at f5.6 and deteriorate toward f11 and still acceptable at f16.

I'm using http://imagefra.me/ (http://picoodle.com/ same site different domain name) for a long time and I never noticied any messing with the photos I have uploaded.

This is an example:

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Last edited by Niko@inScale; June 12th, 2011 at 04:27 PM.
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  #9  
Old June 12th, 2011, 04:48 PM
durangokid durangokid is offline
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Ok guys, I thinks itís starting to make sense. I didnít know that setting the aperture at its highest setting (number wise) would degrade the resolution, I thought it would just give a better DOF. Just to be clear, when you talk about focal length, you mean the distance from the camera to the object correct? I donít understand the mathematical stuff but Iím getting an overall grasp of what you are describing.

So my game plan will be to start my aperture at 8 and work to 16. Iíll let the camera choose the ISO and shutter speed. I did change the shutter speed a bit with the photos above to lighten them up a bit.

Thanks for the help guys and Iíll check out the hosting sites too. I donít mind paying a small fee for hosting if it will help too.
Oh and one more thing, would using the other lens help? It was a lot more money than the kit lens but it sure has to have a lot more distance. That and the DOF is a lot less but I have yet to mess with the aperture settings.


And thanks for the link Aaron, it will give me something to study.
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  #10  
Old June 12th, 2011, 05:42 PM
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Focal length is inner camera thing and roughly this is the distance from the lens to CCD sensor. So your lens is of variable focal length from 28 to 55mm. And your macro 100mm lens is 100mm focal length. But it will lead us to optics science if I gonna explain you that.

And I would use the lowest ISO settings in your place. You don't have to take photos from your hand... use the tripod or improvise some kind of base for camera, so you can shoot the much longer shutter speeds. If you pay attention I have shoot that phantom photo with 1/13sec by relying camera on firm box as the basis. I gave you the best sharpness ranges for each focal length on your lens so it is on you to experiment. When you shooting from tripod or from improvised base, it is smart to use self-timer. Set on couple of seconds and in that way you will avoid any camera shacking as a result of pressing the button! Remote control is even better!

Do you think on 100mm macro that you have or to by another lens? Your wife lens should be by far better quality than yours. Take couple of shots and you will see... much better!
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