TCambell, I absolutely love when you drop by a thread. Thanks for your detailed explanations!
On the topic of prime lenses...I've been toying around in the shop today and I'm noticing that on my smaller items I absolutely love the nifty fifty because of the ability to blur the background.
However on my larger items I'm wondering what lense would produce the same effect? Such as an armoire, or large desk, couch, bed frame...Is there anything that can focus on something so large, from far away yet blur the background? Not sure if I'm getting my issue across, I'll post pictures tonight if nobody gets what I'm trying to say.
The contrast in focus (sharp vs. soft) is based on the "depth of field" produced in that particular image. Depth of field is the range of distances at which the focus will appear to be more or less acceptable to our eyes.
The depth of field is controlled by three factors:
1) The focal ratio used for that image. High f-stops (smaller size aperture openings) produce broader depth of field. Smaller f-stops produce shallower depth of field.
2) The focal length of the lens used for that image. Shorter focal length lenses produce broader depth of field. Longer lenses produce shallower depth of field. I have a 14mm wide angle (which is VERY wide on a full-frame body) and I practically don't need to focus it (almost regardless of f-stop used.)
3) Subject focus distance. More distant subjects have broader depth of field. Closer subjects produce shallow depth of field.
You have to combine all three of these to get the final result. Using a "long" focal length lens at an extremely shallow depth of field with a VERY close focus distance produces "paper thin" depth of field. Using a very wide lens to take a landscape (high focal ratio and vast distances) produces a very very broad depth of field.
A desk or armor are going to be a challenge to produce a soft background because those items are large and framing them requires that you stand at a greater distance. As you do this... the extent to which the background blurs will decrease (it'll be blurred... only mildly so). If the focusing distance is close, then the background blur will be stronger.
So let's suppose you want a photograph of a chair ... and suppose this chair is about 3' wide, 3' deep, and 4' high. Perhaps we dress the shot to add in a plant, a background window or drapery, etc. to dress the shot. I'll arbitrarily choose a dimensional field of view (at the chair distance) of 5 x 7.5'.
I can use this site to find the distance I need to stand to get that framing:
http://www.tawbaware.com/maxlyons/calc.htm
If I look at the "dimensional field of view calculator" and test some values, I find that we'd need to be somewhere around 16-17' away to get that framing. Let's just go with 16' for now.
If I go to DOFmaster.com and use their online DOF calculator here
Online Depth of Field Calculator I can poke in some values to test. Remember... we want a DoF of about 3'.
I'll need to pick a camera body with an APS-C size sensor (the 70D isn't listed but the 60D is... the math will be identical).
I need to pick the 50mm focal length.
I need to pick that 16' distance we established earlier.
Now I can toy with f-stops ... looking for an f-stop that yields about 3' of DOF.
It turns out f/2.8 does this rather nicely (a DoF of about 3 1/3rd feet)
But the next factor is to consider the background. Background elements which are "immediately" behind the chair won't have much blur to them (just a little). The farther back you place them, the stronger the effect of blur. This chair would need to be brought well-forward of any backgrounds.
If we crop in a bit tighter on our "chair" and reduce the focusing distance, we can increase the amount of blur in the background.
Here's where you get to be a little artsy: Is it actually necessary for 100% of a subject to be in tack sharp focus? I'll see people take pictures of food and they want the entire "plate" in the frame and they want it all in-focus. But the photograph is not about the "plate" ... we all know what dinner plates look like. We don't necessarily need to see them and we can even crop out a bit if we want. The image is about the food and while we need a representative sample in sharp focus, we may not necessarily need 100% in sharp focus. You certainly don't want a blurry subject, but there's an artistic judgement you'll need to make about what areas and how much of an object needs to be in tack sharp focus before the viewer gets the idea and doesn't need to see the whole thing in tack-sharp focus. The point here is that you may be able to cheat on your depth of field. You'll need to be the judge as to how much "cheating" is appropriate to achieve the results you want.
I did some scanning through images at Pixel-Peeper.com to look for something taken with the 50mm f/1.8 lens using focal ratios between f/2 and f/2.8 with far enough subject distance that they "might" show results comparable to this chair example (I couldn't find a great representative shot).
These are NOT my images (they come from Pixel-Peeper) so I can't post the images here, but I can post the links. Look at these two:
This one is f/2.8:
https://www.flickr.com/photos/andreas_helke/1351963797/in/photostream/
Notice the background here has only very moderate blur.
This one is f/2.2:
https://www.flickr.com/photos/42193708@N04/3998715439
Now... you're going to need to imagine this shot rotated to a vertical orientation with a chair in it to get the idea. Really I'm trying to show the difference between subject and background blur. This f/2.2 shot obviously shows more blur than the f/2.8 shot... but the blur in the background is not extremely strong (also this shot shows the "nifty fifty's" "nervous" or "jittery" bokeh. The bokeh isn't so smooth or creamy here. This is because the lens has a 5 blade aperture and is not well-rounded. The f/1.4 version of the 50mm lens is a bit higher quality. The f/1.2 version has an even smoother quality but at a CONSIDERABLY jump in price tag.
Given that you're photographing antique furniture, consider broad lighting sources off to the side. This causes the light to cast shadows which reveal surface detail with more dimension to them. Straight on lighting doesn't cast shadows so details in fabrics, carved furniture, etc. will appear more "flat". Light sources off the sides will cast shadows and that cues the eye that the detail has depth ... the details and contours are more visible. Pinpoint light sources cast shadows with harsh edges (rapid transition from light to shadow)... but broad light sources cast shadows with softer edges and look more pleasing.
![[No title]](/data/xfmg/thumbnail/37/37603-739c5d9b541a083a12f2f30e45ca2b7b.jpg?1734170731)
![[No title]](/data/xfmg/thumbnail/37/37605-90c8efaef5b7d1f52d4bf8e7dfd33673.jpg?1734170732)