Full frame or cropped?

NickTB

NickTB

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I have the opportunity of buying either a Sony A55 or a Sony A65. Both are very similar in content but the A65 is full frame. Now do i need to spend another £150 for full frame? MP is 16 and 24 respectively and to be honest it seems at that point I don't need more than 16! But on the other hand is full frame a radically different animal?

And these are bodies only. I'm possibly looking at a Tamron 10-24 for shooting my baby indoors in a low light situation.

Any advice re ff and lenses would be welcome.

Thanks,

Nick
 
scottthehat said:
none of those cams are full frame both are croppers.
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Really? I was going by what the guy in jessops told me today!! Hence my question here.... Glad I'm not buying one from them then!
 
Aside from the issue with the jessops info, there were two points to your question;
1) crop vs full frame
2) tamron 10-24 for low light portraits

The first question is quite an animal of a question. The only ff Sony bodies are the A900 and A850 - although updates are expected in the next 6-12 months. The advantages of full frame are less distortion at wide angle and better bokeh*. Historically, the A900 and A850 have also been famed for their AMAZING viewfinders, they really do give you a huge image of what you are shooting, but the new electronic viewfinder on A65 and A77 now offer a similarly impressive viewfinder, albeit with a few limitations of electronic viewfinder (best to test it out in store yourself to see).

Given your needs, I would suggest a crop body, simply because they're cheaper and if you're coming from the Nex system you'll be used to the crop sensor size, and as such what composition/magnification you can expect from the focal lengths.

Regards to the second point, I wouldn't get a tamron 10-24 for portraits. It's a very wide lens (crop body only by the way), and won't give you the out of focus areas you want in portraits without being incredibly close to the subject (and thus distorting their face and features). You will probably be best served by the tamron 17-50 f2.8 and/or a 50mm f1.8 (or f1.7) prime lens. The former will give you more flexibility in terms of it's zoom, but the latter will give you better image quality and more flexibility in terms of depth of field and bokeh. Both would serve you well in low light, but more so the prime lens.


*this latter point will no doubt have the arguments rolling; but for the same composition of an image with a lens on ff vs. crop, you need to be closer to the object with a ff, and thus the dof is smaller and bokeh more impressive.
 
Thanks for the reply tricky. Just looking about and digitalrev have an A55 bundle including the Sony 50mm f1.4 AF lens for a reasonable price. I have always liked the canon 50mm. Is this a similar performer?
 
bokeh specifically is the appearance of the out of focus areas in a picture and is a property of the lens and has nothing to do with the camera.

What changes with sensor size is the depth of field, i.e. how much of the picture is in focus.

There are pluses and minuses with regards to FF vs. crop depth of field differences.
 
Both have the same sensor but to get an extra 8Mp's on it I think might be overcrowding it a bit. My Canon 7D has an 18Mp sensor and gives me brilliant, bright and sharp images with good ISO handling. Putting the extra photosites on the same sized sensor means they have to be smaller so wont gather the light as well. As I've got a Canon 5DMkII with 21Mp's from a larger sensor I can say IMO that the IQ of the 5DMkII is slightly better than the 7D, so I would think that the IQ on the 16Mp a55 will be similar to the 7D.
 
NickTB said:
I actually added this to the bag, but cancelled it when the postage was £50!
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Can you please let me know the exact items you are purchasing? I have tried adding the Sony A65 and Tamron 10-24mm, which is around £30 for shipping, not £50.

There is also an extra £10 off as forum member, which I can provide the coupon code to you via PM once you confirmed.

Please let me know. :)
 
Nawty said:
What changes with sensor size is the depth of field, i.e. how much of the picture is in focus.
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This myth again? :D Sensor size does not affect DoF. When you use a smaller sensor you are effectively just cropping an existing picture and taking a pair of scissors to a photograph can't change the DoF.

Sensor size will however influence what lens you use and the camera to subject distance and framing and the apertue you use (because you've changed the camera to subject distance) and these are the things that make the DoF look different, but the actual size of the sensor in itself can not affect DoF.
 
woof woof said:
This myth again? :D Sensor size does not affect DoF. When you use a smaller sensor you are effectively just cropping an existing picture and taking a pair of scissors to a photograph can't change the DoF.

Sensor size will however influence what lens you use and the camera to subject distance and framing and the apertue you use (because you've changed the camera to subject distance) and these are the things that make the DoF look different, but the actual size of the sensor in itself can not affect DoF.
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so we should all buy point and shots, beacuse the af is the sme the imagea quality is the same in print and depth of field is the same, my misses will be happy.
 
woof woof said:
This myth again? :D Sensor size does not affect DoF. When you use a smaller sensor you are effectively just cropping an existing picture and taking a pair of scissors to a photograph can't change the DoF.

Sensor size will however influence what lens you use and the camera to subject distance and framing and the apertue you use (because you've changed the camera to subject distance) and these are the things that make the DoF look different, but the actual size of the sensor in itself can not affect DoF.
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Tee hee. Groundhog Day returns ;)

DoF is only apparent when you render the image, not when you capture it. I can take a photo from any sensor and the depth of field varies depending on how big I print it and how far away I view it.

Sensor size affects that as for any given print size, you are magnifying the image more or less depending on the size of the sensor. A smaller sensor needs to have bigger magnification than a larger sensor for a given print and will actually give a shallower depth of field accordingly, all else being equal.
By magnification, I mean to make a print at 36cm along the longest edge, for a full frame sensor at 3.6cm along the longest edge, I'm magnifying it by 10. For an APS-C sensor at 2.36cm along the longest side, I have to magnify it by 16 to get the same print size.
 
DigitalRevDeals said:
Can you please let me know the exact items you are purchasing? I have tried adding the Sony A65 and Tamron 10-24mm, which is around £30 for shipping, not £50.

There is also an extra £10 off as forum member, which I can provide the coupon code to you via PM once you confirmed.

Please let me know. :)
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It was the 50mm f1.4 bundle
 
scottthehat said:
so we should all buy point and shots, beacuse the af is the sme the imagea quality is the same in print and depth of field is the same, my misses will be happy.
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Er... dunno about you or your Mrs. but when I'm using a P+S I'm probably using a 6mm lens at f4 or summot like that, not an 85mm at f1.4. If you can't see the effect that'll have then it's back to basics for you for a few days :D
 
arad85 said:
Tee hee. Groundhog Day returns ;)
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It's such an often repeated thing that I worry that newbies like me will end up believing it when it's soooooo much more interesting to have a better understanding of what's actually happening so you can work with the limitations / advantages and just plain extra choices different formats give even if in practice it may for some make little difference if (although wrongly) they believe it.
 
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arad85 said:
Sensor size affects that as for any given print size,
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No. By playing with print sizes all you are doing is making the attributes of the image more or less visible. That'll affect how we see the image and the DoF etc but it doesn't actually change anything. It's all still there and it is what it is.
 
woof woof said:
No. By playing with print sizes all you are doing is making the attributes of the image more or less visible. That'll affect how we see the image and the DoF etc but it doesn't actually change anything. It's all still there and it is what it is.
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You're missing the point that everything outside of the plane of focus is out of focus to some degree or other. Assuming a perfect lens and infinite pixels (so you never get to a point where lens resolution or pixel density is the defining factor) you could have an image shot so DoFmaster says the DoF extends from 1m to infinity, but by blowing up the image, you could get a DoF which is in inches. Same image, just a different rendition.

DoF is a perceived thing and depends on how much you magnify the sensor image for print, and how far away you view it from. Out of focus is a physical thing and in any picture, out of focus is anything off the focus plane (which may not be flat, but that's something else). Whether or not it is perceived to be out of focus depends on how big you print it. Sensor size affects it simply because with a larger sensor you have less enlarging to do to get to a specific print size.

If you don't believe me, take a look at this picture shot at 17mm and F4 with a 5D2.

http://www.arad85.co.uk/hosted/talkp/_8439.jpg

DoFmaster says the depth of field should extend to infinity. It does if you view it full screen (i.e. shrink the image so it fills the screen), but it doesn't when you pixel peep. That's because if you view it on a 24" monitor at 1920 pixels wide, and view it from 50cm (my viewing conditions), you've magnified the original image far beyond the "normal" range for depth of field calculations. You're now seeing the out of focus areas more clearly - the DoF is far reduced, probably to a few metres.
 
woof woof said:
when it's soooooo much more interesting to have a better understanding of what's actually happening
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Yes. I agree. What I am describing is how it works - it's simple physics. You just don't seem to be understanding how all of this hangs together fully.

DoF has nothing to do with image capture but all to do with how the image is rendered. Simple as.
 
arad85 said:
You're missing the point
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No I'm not. The image is what it is and by printing it bigger or smaller or looking at it from an inch away or from a mile away you can't alter what it is. Nor can you alter it by cutting bits off it.

If you don't believe me get hold of a 35mm negative and look at it close up and then from the other side of the room and then print it out at different sizes. Whatever you do you can't change the DoF / field of focus of the nagative. It just is what it is and all you can do is alter how you percieve it... but that's not the same as being able to change what it is. Shoot the shot and the DoF and everything else is set and mucking about with print sizes can only affect how you perceive it at your viewing distance.

The reason I've said that the sensor doesn't change the DoF is to prompt anyone who believes that it does to think about it. If after thinking about it they want to believe that format size affects DoF (rather than affecting the decisions you make which go on to affect DoF) then I'm happy for them :D
 
arad85 said:
DoF has nothing to do with image capture but all to do with how the image is rendered. Simple as.
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Well, obviously I disagree :D The image is captured set when you press the shutter :D and the DoF will be visible on the negative :D before you decide what print size you are going to produce.
 
woof woof said:
Well, obviously I disagree :D The image is captured set when you press the shutter :D and the DoF will be visible on the negative :D before you decide what print size you are going to produce.
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Tee hee... What you have captured is points that are in focus and those that are out of focus. Whether you see them as in focus or out of focus depends on how big you print that "negative" and how far away you view it.

That's all there is to it. Nothing more, nothing less.
 
woof woof said:
If you don't believe me get hold of a 35mm negative and look at it close up and then from the other side of the room and then print it out at different sizes.
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They will have different DoF but they will also have the same in focus points and out of focus points. Depending on size and viewing distance, some of the out of focus points will appear to be in focus. That's why DoF changes. Whether something is in or out of physical focus doesn't change and it is that you capture.

Once you split image capture (whether the image object is sharply focused or not) away from print (which gives you your perceived depth of field), it all falls very neatly into place.

Have a look at that image I linked to if you don't believe me. With it displayed on my screen so that I can see the whole picture (i.e. at ~700x1024) it looks to have infinite DoF. Click on it so you are pixel peeping and all of a sudden the DoF changes. Image is the same, DoF changes due to the rendering.
 
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arad85 said:
Yes. I agree. What I am describing is how it works - it's simple physics. You just don't seem to be understanding how all of this hangs together fully.

DoF has nothing to do with image capture but all to do with how the image is rendered. Simple as.
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Yes.

woof woof said:
Well, obviously I disagree :D The image is captured set when you press the shutter :D and the DoF will be visible on the negative :D before you decide what print size you are going to produce.
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Alan, you are not allowed to disagree ;) Because that's what DoF is. For DoF to exist, you have to look at a finished rendering, the final output and preferably a print to show it properly.

The concept of DoF includes a whole raft of parameters, some of which we take for granted because they are laid down by international standards, and some that we as photographers can adjust.

The whole shooting match (haha!) includes the sensor size, subject distance, focal length and f/number. In addition, the print size, viewing distance and circle of confusion that is laid down. You will notice that every single one of these parameters is a component of magnification, even the f/number because of the phyiscal diameter of the aperture. DoF is the net effect of all those factors, and if you change any one of them the whole calculation changes.

So, if you want to be picky about it, you have to specifiy every one of those things every time you refer to a DoF change. But since nobody ever does that, various shorthand phrases are used, and there's one in particular that you continually object to, which is "smaller sensors give more DoF, and larger ones less."

Now you might not like that, but most people find it acceptable because in actual picture taking it's the one you can't change because it's set by the camera and everything else is adjusted accordingly. You might say that it's the shorter focal length lenses used on smaller format cameras that changes the DoF, but the only reason you have to do that is because the sensor size has changed.

The sensor size is fundamental, and it drives every other decision because that's the way we work - fixed sensor size, and lens focal length adjusted accordingly. If we worked the other way around with a fixed lens and then adjusted the sensor size to change framing, you might have a point, but we don't.
 
Let's try this mathematically (the more Alan baulks at this, the more it forces me to understand what is actually going on ;)).

From: http://dofmaster.com/equations.html you can see that Hyperfocal distance is related to circle of confusion. Hyperfocal distance is used (together with lens focal length and distance to subject) to give you near and far distance of acceptable sharpness.

Looking here: http://en.wikipedia.org/wiki/Circle_of_confusion you can see that CoC is defined as:

CoC (mm) = viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25

This is all to do with output parameters. The KEY thing here is enlargement. This is defined as the amount you are enlarging the captured image to get the printed image. I.e. for a full frame sensor at 3.6cm on one side, if you're printing at 36cm along the longest edge, the enlargement would be 10. The higher the enlargement, the smaller the CoC becomes.

These formulae directly relate sensor size to perceived depth of field. I don't see how much clearer this could be.....
 
And it was predicted that this banter would be summoned...

Tricky01 said:
*this latter point will no doubt have the arguments rolling; but for the same composition of an image with a lens on ff vs. crop, you need to be closer to the object with a ff, and thus the dof is smaller....
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...although there was one fatal error in his thinking...


Tricky01 said:
...and bokeh more impressive.
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As noted by someone above, the bokeh is lens specific. However, the DoF - DEPTH of field - IS impacted by the sensor size if you are composing the identical shot on a crop and a ff.

Depth of field is a CALCULATED via the following equation:
http://www.dofmaster.com/equations.html
Where:
H - is the hyperfocal distance, mm
f - is the lens focal length, mm
s - is the focus distance
Dn - is the near distance for acceptable sharpness
Df - is the far distance for acceptable sharpness
N - is the f-number
c - is the circle of confusion, mm

Now without even looking at the calculation, we know that if we use the same lens with the same settings, then all of the above variables are constants, except one; 's' - the focus distance, and now I'll explain why;

If we want to FRAME precisely the same shot with both a full frame camera and a crop sensor camera, we will need to be CLOSER to the subject with the full frame camera, and FURTHER away from the subject with the crop sensor camera. Therefore, for each identically FRAMED photo, 's' is smaller when shot with the full frame camera.

Now all you need know is if all variables except 's' are constants, then as 's' tends to zero (shorter focus distance), the depth of field also becomes smaller - or shorter.

So what does that mean? It means the area of the image which appears 'sharp' (or in focus) just in front and just behind the distance at which you focused is smaller; throwing the foreground and background out of focus and making the area in focus stand out more. This video here:
http://www.youtube.com/watch?v=mFf6zhbhI8Y helps with DoF and although John also did a BRILLIANT session explaining crop vs. ff, it's not on youtube (so go buy the class, it is worth every penny!)
 
arad85 said:
I don't see how much clearer this could be.....
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You couldn't be more right, and I wish I'd read your post before reading half way down and then writing my reply! :clap:
 
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