Will a 50mm 1.2 lens on a crop camera like the Rebel XTi require the same shutter speed if placed on a fullframe back like a 5D Mark II?
Taking a portrait.
Distance from subject is fixed. (I realize that the crop camera will have a slightly larger zoom because it is functioning in my case with a 1.6 crop making the 50mm work like an 80mm.)
Lighting is fixed.
Lets say the aperture is set to 1.2 to make a small depth of field and blur the background a bit. Lets also set the ISO at 100.
Now my assumption is because a I'm using more of the focal plane of the lens (IE I'm not cropping it.) and my sensor is larger(IE Each pixel is actually larger meaning it pulls in more light.) I should see a reduction in shutter speed or in other words it will be faster.
If this is the case is there anyway to calculate this difference or maybe a website that might show me/explain to me the difference?
Thanks,
Shelby Hl
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M$3 Answers
Because of this standardized nature of ISO, exposure for any camera in ambient lighting conditions can even be calculated using tables like this one: http://www.calculator.org/exposure.aspx
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M$In an age of digital and photoshop, it may not make sense to tell you that if you made mistakes with f-stop or aperture with a film camera using different film speeds, you could more easily visualize how these things work. While mistakes may not be welcome, you do learn from them.
ISO and ASA in film indicate how much light is necessary to expose the film to in order for the image to be captured. Film speeds when I started learning photography were around ASA 64, and a typical daylight exposure might require 5.6 or 8 at 125 or 250. As the ASA/ISO numbers went higher, the film required less light to set the image, so you could get better results in low light. If you used 400ASA in the daytime you pushed the settings up to 16 or 22 on the aperture and used a high f-stop, maybe as much as 500 or 1000.
In digital cameras, to create that effect, there are ISO speeds so you can do the same tricks with the camera that you could with film. If you want a grainy fast shot with higher contrast, set the ISO high, if you want rich colors and have a sedentary or slow moving subject, set the ISO low. It sounds like you've figured out depth of field. http://www.photonhead.com/beginners/filmspeed.php
Your question said
>>>>Now my assumption is because a I'm using more of the focal plane of the lens (IE I'm not cropping it.) and my sensor is larger (IE Each pixel is actually larger meaning it pulls in more light.) I should see a reduction in shutter speed or in other words it will be faster.<<<<
You're asking about the speed of the shutter, based on the receptiveness of the sensor. The laws of physics and the speed of light would dictate that your light isn't any faster, it's all in how you set the ISO with it's sensitivity to the light. It may be acting more like a film camera with the size of the sensor, but light isn't traveling any faster through the lens to reach it. The sensitivity of the good digital camera versus a film camera with the same ISO or film setting is going to yield a comparable photo, with the difference being that if both are enlarged, the film camera will come up with an image that is much larger than the digital camera, but the digital camera will come up with a crisper image when they're both at their optimum enlargement.
Here is a web site where the photograph describes in great detail how he tested a Pentax film and a Canon digital camera, setting up tripods side by side and using comparable settings. If you work your way through you'll see his examples of the relative merits and differences between the cameras. http://www.luminous-landscape.com/reviews/shootout.shtml
With your digital camera, pay attention to your ISO speed, and as you're learning to do this, bracket your photos. If you're consistent in your bracketing so you can remember what you did, you should be able to see the difference. Set the ISO, set the aperture, and leave the f speed on automatic. Then, leaving the ISO where it is, set the f speed, and leave the aperture on automatic. And try a few on the camera's auto setting.
When you get back to your computer, load these into a folder, and open it in Adobe Bridge so you can see all of the metadata for each shot. As you review the results you should be able to compare the settings and see what worked best.
I am not a professional photographer, and when I use the digital I use some features and not others. I am more conversant with the film camera and how it works, so what I am trying to explain here is how the sensor may be working based upon film camera (ISO) terms. I suppose if film had never come along first, digital cameras wouldn't have these faux-film settings, they would just get on with what they need to do. How we do things now is based upon how things used to work. Did you know that the gauge of standard railroads has a correlation to the distance between yoked horses or oxen pulling a carriage? And that we "dial" our cell phones? There are a lot of artifacts of old technology embedded in the new, because of what we understand about how things work. I think you'll find that if you can come to a clearer understanding of what was going on with film cameras and film speed, you might sort out what the digital camera is trying to emulate.
Good luck with your photos. The really great thing about experimenting with the digital camera is that it is a heckuva lot cheaper since it doesn't waste film! :)
Film speed information http://www.photonhead.com/beginners/filmspeed.php
http://www.luminous-landscape.com/reviews/shootout.shtml
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M$
I tried to respond and it went away.
This was a difficult, multi-part question, in which it sounded like the speed of light was the focus, based upon the sensitivity of a larger sensor in the new camera, but the ISO setting is the factor he needs to consider, and the f-stop shouldn't be any faster if the both sensors accurately mimic the ASA/ISO rating of film.
I originally started this with "the short answer is 'yes'" but then edited that out, because it didn't mean a lot unless there was some discussion of the issues involved. But I'll add it back in here, in case it isn't spelled out clearly in my answer. I think if you move this lens from one camera to the other (lucky it fits!) the nature of the sensor shouldn't change the shutter speed. The main "speed" discernible involved the operation of the camera (any digital camera) has to do with the time it takes to write to the memory card. But that's a different question. . .
Not to argue for or against the answer, but one aspect of the answer is incorrect. The speed of light has absolutely nothing to do with the shutter speed or ISO settings. The aperture and shutter speed simply determine how much light (i.e. how many photons) will reach the sensitive medium (film or sensor). This is simply because as you open the shutter wider, photons that might have hit outside the aperture with a narrower setting will make it to the medium. Similarly, a slower shutter speed will allow photons that arrive later to still get in.
So, to summarize, you might see a difference in low-light situations. However, with digital cameras, camera settings and performance (hardware/software) will likely have a far larger impact than the sensor size. For instance, if the cameras you use have different noise processing, the net benefit of the larger sensor size could easily be lost.
I have never found a website that provides that information, and I'm not sure you could accurately measure the difference. Hope that helps.
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M$
ISO determines the sensitivity of your sensor. A lower ISO rating will require a longer exposure to allow in the same level of light. A lower ISO will reduce digital "noise" in your image.
A f/1.2 lens (wide open) will have a VERY shallow depth of field. So much so that many photographers will think their image is out of focus when all that has happened is they (or their subject) has moved slightly before the shutter is activated.
That same lens can have a narrower aperture just like any other lens (such as f/16) and take a similar image to other lenses. The quality of the image captured will depend on the quality of the glass and noise reduction (through lower ISO or post processing in-camera or via software). The 50mm f/1.2 is a high quality lens. The downside is that focusing takes longer than say the 50mm f/1.4 (which I own) and it's way more expensive. The 50mm f/1.8 is cheaper, but the quality of the images (some say) is also cheaper. The construction of the f/1.8 is also cheaper (easier to damage, but at such a low cost also easier to replace).
Using the chart @sutherland linked to can help you. Just keep in mind that the lowest ISO that allows you the proper exposure time to get your image is going to have the least digital noise.
That link to the chart is what made the answer work for this asker, I think. I've bookmarked it myself. ;-)